2026 天文年會 (ASROC Annual Meeting)

May 15, 2026, 12:00 AM → May 17, 2026, 3:30 PM Asia/Taipei

College of Hakka Studies at NYCU, Zhubei, Hsinchu County 國立陽明交通大學客家學院(竹北六家校區)

Welcome to the ASROC 2026 Annual Meeting

The 2026 Scientific Assembly of the Astronomical Society of the Republic of China (ASROC2026) will be held at the College of Hakka Studies at National Yang Ming  Chiao Tung University in Zhubei on May 15 (Friday) – May 17 (Sunday), 2026.

This year, the plenary talks will be given by Prof. Hisashi Hayakawa (Nagoya University) and Prof. Sebastien Charnoz (Université de Paris Cité), and the talk’s titles are “Investigations for Historical Archival Records and Reconstructions of Centennial Solar Activity” and "Condensation of the first solids of the Solar System in fast non-equilibrium process: a new way to oxidize planets".

A competition for the best oral and poster awards for students will be held during the meeting. The best student oral presentation will be awarded with NTD 10,000 prize, and the three best student posters will be awarded with NTD 5,000 prize. The three best poster winners need to give a 3-minute oral presentation at the general assembly meeting.

The registration and abstract submission are now open. The deadline for abstract submission is April 10th, and for online registration is April 26. Participants of the scientific assembly should submit their abstracts and register online. A registration fee of NTD 2,500 (NTD 1500 for students) should be paid on site or via bank remittance. After completing the transfer, please remember to enter the last 5 digits of the transferring bank account on the registration page. The bank information of ASROC is: Hua Nan Bank (華南商業銀行), Bank code: 008. account# 154-10-000602-3, account name: 中華民國天文學會, branch: 台大分行.

歡迎來到2026天文年會

2026年中華民國天文學會年會將於2026年5月15至5月17日（星期五、六、日）於國立陽明交通大學客家學院(竹北六家校區)舉行。這是國內天文工作者一年一度發表研究的新發現和工作成果的聚會，也是適合交換研究心得或洽商研究合作的場合。歡迎所有與天文和天文物理研究、天文教育（國小、國中、高中及大專院校）、以及天文推廣工作（如社團、社區大學、天文館、科博館等）相關領域的口頭成果報告或壁報論文。

此次年會中除了會員大會、學術論文報告、壁報論文、天文教育和業餘天文活動報告等之外，亦安排兩場大會專題演講，特別邀請早川尚志教授（名古屋大學​​）與 Sebastien Charnoz （巴黎城市大學）教授進行大會專題演講 。演講題目分別為 “Investigations for Historical Archival Records and Reconstructions of Centennial Solar Activity”與"Condensation of the first solids of the Solar System in fast non-equilibrium process: a new way to oxidize planets"。

年會設有最佳學生口頭報告獎一名，頒發獎金新台幣10,000元。最佳學生壁報獎三名，每名頒發獎金新台幣5,000元（壁報獎得主必須準備3分鐘演講於5月17日會員大會中報告）。敬請把握摘要投稿截止日期踴躍投稿。

2026年天文年會之網站已經啟動，有意參加年會者請至天文學會網站報名。摘要上傳截止日為 4月 10 日，線上註冊截止日為4月 26 日。一般會員註冊費為新台幣2500元，學生會員註冊費為新台幣1500元，請於會議現場繳交或透過銀行匯款（會員得以該年度學會年費抵免註冊費，永久會員可免繳註冊費）。匯款後請記得在報名頁面提供匯款銀行之末五碼。匯款帳號資訊：華南商業銀行台大分行 (銀行代號：008)  帳號 154-10-000602-3   戶名:中華民國天文學會 。

 

 

年會議程委員會 Program Committee
江國興（清華大學 天文所；主席）
王祥宇 (中研院 天文所)
李景輝（中研院 天文所)
秦一男 (淡江大學 物理系)
曾瑋玲 (師範大學 地科系)
潘彥丞（中央大學 天文所)
賴詩萍 (清華大學 天文所)
郭政育（中山大學 物理系)

年會組織委員會 LOC
江國興（清華大學 天文所）
譚雪瑩（陽明交通大學 物理研究所）
潘國全（清華大學 天文所）
高筱茵（清華大學 天文所）

主辦/協辦/贊助單位/Sponsors
國立陽明交通大學(NYCU)
國立清華大學(NTHU)
國家科學及技術委員會(NSTC)
物理研究推動中心(PRPC)
國家太空中心(TASA)
台灣天文研究聯盟(TARA)

 

ASROC 2026.pdf

contributions.pdf

新竹安捷-2026天文年會訂房單Rebecca260129.pdf

Fri, May 15

Registration

Opening ceremony

Convener: Albert Kong

Plenary

Convener: Sut-Ieng Tam (NYCU, IoP)

1 Early Planet Formation in Embedded Disks in Ophiuchus (eDisk@Oph): Project Overview and Recent Progress

As an extension of the ALMA Large Program Early Planet Formation in Embedded Disks (eDisk), we are conducting a survey of a homogeneous sample of 25 protostars in the Ophiuchus star-forming region (eDisk@Oph). The targets were selected from the Spitzer c2d catalog based on their bolometric luminosities and near-infrared spectral indices. The primary scientific objective of this project is to measure the dynamical masses of the protostars and to investigate their relationship with disk properties.

Among the 25 sources, 19 were newly observed with ALMA in Cycles 10 and 11 in Band 6, obtaining 1.3 mm continuum emission as well as several molecular lines, including CO isotopologues such as C$^{18}$O (2–1). For the remaining six sources, comparable datasets were retrieved from the ALMA archive. The typical angular resolution of the observations is ∼0.14″–0.17″, with sensitivities of ∼30 μJy beam$^{-1}$ for the continuum and ∼2–4 mJy beam$^{-1}$ per channel for the molecular lines.

The 1.3 mm continuum emission is clearly detected toward all 25 protostars, revealing a wide diversity in source sizes spanning approximately one order of magnitude; in several cases, the emission is not fully spatially resolved. A subset of the sources are identified as binary systems. Compact C$^{18}$O emission associated with the continuum emission is detected in a fraction of the sample, while compact $^{12}$CO (2–1) emission associated with the continuum emission is detected toward all sources except one. These compact emissions are considered to trace either envelopes or disks associated with the protostars.

In this presentation, I will provide an overview of the eDisk@Oph project and report on the current status and recent progress of the data reduction and initial analysis with particular emphasis on the velocity structures of the molecular emission.

Speaker: Nagayoshi Ohashi (ASIAA)

2 First High-Resolution ALMA Observations of the Protostellar Jet HH 212 in SiO J = 16–15

HH 212 is a nearby protostellar jet driven by the Class 0 protostar IRAS 05413–0104, exhibiting a highly symmetric morphology with well-defined knot structures close to the disk. Previous ALMA observations have mapped HH 212 in the SiO J = 8–7 transition (Band 7). Here, we present the first high-resolution observations of the higher-J transition, SiO J = 16–15 (Band 9).

We find that the knots exhibit smaller Gaussian radii, narrower line widths, and lower brightness in Band 9 than in Band 7. These results can be understood if the jet has a decreasing radial density profile and a significant radial velocity component, as predicted by the X-wind model (Shu et al. 1995; Lee et al. 2022).

Assuming a radial density profile derived from the X-wind model, we construct a simple non-LTE model that reasonably reproduces the observed jet geometry and line ratios and highlights the importance of non-LTE effects in higher-J transitions. Our results confirm the previously adopted physical conditions in the innermost jet and provide further support for the X-wind model in generating protostellar jets.

Speaker: YU-SYUAN TU (中研院天文及天文物理研究所(ASIAA))

First High-Resolution ALMA Observations of the Protostellar Jet.pdf

3 COMPASS - inventory of sulfur-bearing molecules toward BHR71-IRS1

Sulfur is the tenth most abundant element in the universe. It is found in various biomolecules from amino acids to lipids. In space, most of the sulfur is thought to reside on and inside dust grains during the early stages of star and planet formation. Sulfur-bearing molecules have also been detected in comets. To better understand the sulfur trail from diffuse ISM to planet-forming materials, we analyze the unbiased spectral survey data from the ALMA Large Program “Complex Organic Molecules in Protostars with ALMA Spectral Surveys” (COMPASS). We will present one of the first results of COMPASS focusing on the sulfur-bearing molecules toward the embedded protostar BHR71-IRS1.

Speaker: Daniel Harsono

4 Physics-Informed Neural Network for Kilonova Light Curves Modeling

Physics-informed neural networks (PINNs) have gained considerable importance in recent years in the domain of Astronomy \& Astrophysics, particularly as a potential tool to solve differential equations within the given boundary conditions, not only for making accurate predictions but also for providing an efficient approach for large computations. In this work, we have focused on solving the kilonova equations adopted from a specific kilonova model through the direct implementation of the PINN on the differential equations and the respective boundary conditions provided in the model. The PINN architecture is trained on differential equations conditioned on certain boundary conditions, thus learning the evolution of KNe light curves based on given ranges of physical parameters. To test the performance, after successful training, predictions of the light curve for a known set of physical parameters are given as input, and a comparison is made between the true and predicted light curves. Current results point to stable training with significant recovery of the light curves, showing a low mean squared error between them. Training and inference for the light curves are completed in under 2 hours. The ultimate goal is to develop an accurate PINN-based kilonova model for light-curve generation and low-latency parameter estimation.

Speaker: Surojit Saha (Institute of Astronomy, National Tsing Hua University, Taiwan)

5 A measurement of the Hubble constant with angular cross-correlation between fast radio bursts and galaxies: application to the Second CHIME/FRB Catalog

The precise measurement of the Hubble constant remains a central challenge in modern cosmology, particularly given the tension between early-universe ( cosmic microwave background) and late-universe ( Type Ia supernovae) measurements. Independent probes are essential for clarifying the origin of this discrepancy. Fast Radio Bursts (FRBs) possess the potential to offer a unique alternative. The unique measurement of FRBs, dispersion measure (DM) in the intergalactic space, serves as a proxy for the cosmological distance measure. Combined with independent measurements of redshift (z), the DM-z relation can constrain the Hubble constant, analogous to the Hubble diagram for Type Ia supernovae. However, largely due to the observational challenges of precise localization, fewer than 10% of the total FRB samples have identified host galaxies, limiting the statistical power of their cosmological utility. To address this, we propose a statistical method using the angular cross-correlation between FRBs in wide-field surveys and galaxies in large-scale galaxy surveys. By correlating FRBs in DM bins with galaxies in redshift bins, we reconstruct the probability distribution on the DM-z plane without requiring individual host identifications. This method enables us to measure the Hubble constant using unlocalized FRBs, which significantly outnumber the localized ones, thereby providing strong statistical power owing to their large numbers. We will demonstrate this method with mock-FRB samples and will present preliminary results using the latest data from the second CHIME/FRB Catalog and DESI Legacy Imaging Surveys. Our results demonstrate the potential of FRB-galaxy cross-correlations as a robust, independent cosmological probe.

Speaker: Tomoki Wada (Tohoku Univ/ NCHU)

6 Simulating AGN feedback in galaxy clusters with pre-existing turbulence

Feedback from active galactic nuclei (AGN) is believed to play a significant role in suppressing cooling flows in cool-core (CC) clusters. Turbulence in the intracluster medium (ICM), which may be induced by AGN activity or pre-existing motions, has been proposed as a potential heating mechanism based on analysis of Chandra X-ray surface brightness fluctuations. However, subsequent simulation results have found the subdominant role of turbulence in heating the ICM. To investigate this discrepancy, we perform three-dimensional hydrodynamic simulations of a Perseus-like cluster including both AGN feedback and pre-existing turbulence, which is stirred to the observationally constrained level in the Perseus cluster. Our results indicate that, although the velocity field is dominated by the pre-existing turbulence, AGN heating through bubbles and shocks remains significant. More importantly, analysis of the velocity structure function and the energy power spectrum shows that the turbulent heating rate is smaller than the radiative cooling rate, especially in the cluster core. Our results offer insights relevant for recent XRISM observations and indicate that turbulent heating alone cannot offset radiative cooling in CC clusters.

Speaker: Jia-Lun Li (清華大學天文所)

7 Revealing the Configurations of Near-Resonance Exoplanetary Systems through Long Baseline Transit Timing

The possibility that there is a third planet in Kepler-396 system was proposed, but not yet confirmed. In order to investigate this, and understand Kepler-396 system’s configuration, new TESS data are employed to form a long baseline transit timing. Our results support the existence of a third planet. With updated parameters, the planet properties are further investigated. In addition, as three planets are near resonances, dynamical simulations are performed to examine whether it is a new resonant chain. Moreover, through transit timing, the main results of several other interesting systems we obtained and published will be reviewed and summarized.

Speaker: Ing-Guey Jiang (National Tsing Hua University)

Coffee break and poster session

Supernova and exotic transients

Convener: Yen-Chen Pan (National Central University)

8 SN 2024ahr: A Type-Ic Superluminous Supernova Featuring a Rare Pre-Peak Bump and Exceptional Nickel Production.

We present a comprehensive analysis of the nearby Type-Ic superluminous supernova (SLSN) 2024ahr at a redshift of z = 0.086. The event exhibits an unusually high late-time 56Ni mass of ~5.5 M☉, derived from nebular spectral synthesis modeling, and shows notable similarities to SN 2007bi in both light curve evolution and spectroscopic properties. The light curve shows a pre-peak bump lasting ~23 days, with a slow rise of ~77 days to a peak absolute magnitude of r ≈ −21.4 mag. We interpret SN 2024ahr as an extremely energetic core-collapse supernova powered primarily by a magnetar central engine. The pre-peak bump is modeled using a magnetar-driven shock breakout framework with TransFit, while the overall light curve modeling with MOSFiT magnetar model yields a spin period P_spin = 0.95 ms, magnetic field B = 2.5 × 10^14 G, and ejecta mass M_ej = 64.29 M☉. Early-time spectra display the characteristic W-shaped O II absorption feature, which fades near maximum light, while late-time spectra (+268 and +450 days) are dominated by nebular emission lines and host-galaxy features. Spectral modeling with SYN++ identifies the dominant absorption features across epochs, providing a consistent description of the spectroscopic evolution. Overall, SN 2024ahr represents an extreme magnetar-powered Type Ic superluminous supernova with a large nickel yield.

Speaker: Aiswarya Sankar Kachiprath (National Central University)

9 The Role of Binary Interaction in Shaping Supernova and CSM Properties

Binary star interactions play a critical role in shaping the circumstellar medium (CSM) and influencing the observational properties of supernovae (SNe). This study focuses on the mass-loss processes in interacting binary stars with solar-like metallicity, particularly in the Case C systems where mass transfer occurs during the donor star's secondary expansion phase, which follows helium ignition. Using the MESA stellar evolution code, we simulate binary stars across a grid of donor star masses and orbital separations. We aim to understand the mass transfer dynamics, the resulting CSM structures, and their influence on SNe progenitor classifications. This project combines numerical simulations with observational results, comparing SNe observations with our models and interpreting the resulting CSM properties. The outcomes will provide a comprehensive framework linking binary stellar evolution, mass-loss mechanisms, and SNe diversity, offering new insights into the physics of interacting supernovae.

Speaker: Sung-Han Tsai (ASIAA / NTU Department of Physics)

10 Impact of chiral neutrino radiation on core-collapse supernova dynamics

Chiral effects induced by quantum anomalies, such as the chiral magnetic effect, are expected to influence the dynamics of core-collapse supernovae (CCSN). These effects arise in strong magnetic fields and rapid flows, which are common in supernova cores. In this work, we investigate the dynamical relevance of chiral neutrino radiation transport in CCSN, focusing on near-equilibrium contributions to the neutrino radiation energy-momentum tensor based on the formulation of Yamamoto & Yang (2021). Using data from two-dimensional CCSN simulations with neutrino transport, we evaluate the chiral radiation source term. We implement the chiral neutrino radiation term into the FLASH simulation code and investigate its impact on the hydrodynamic evolution, with self-consistent coupling in progress, to explore whether it may contribute to neutron star kicks.

Speaker: Chang-Mao Yang (NTHU)

11 Binary Pathways to Fast-Rotating Core-Collapse Supernova Progenitors through Chemically Homogeneous Evolution and Common Envelope Tidal Spin-Up

Identifying the progenitors of rapidly rotating core-collapse supernovae (CCSNe) is crucial for understanding the formation of magnetars and the origin of long gamma-ray bursts. In this study, we investigated the evolution of mass-transferring binary systems in a low-metallicity environment ($Z = 10^{-3}$) using the MESA stellar evolution code. We explored a parameter space with initial mass ratios ($q$) from 0.5 to 0.8, orbital periods ($P_\mathrm{i}$) from 8 to 18 days, and donor star masses ($M_\mathrm{d,0}$) from 20 to $65 M_\odot$. By evolving these systems until the onset of core collapse, we compared their pre-supernova properties with single-star models. We found that the accretor stars bifurcate into two distinct evolutionary pathways. A fraction of the accretors undergo Chemically Homogeneous Evolution (CHE) due to efficient rotational mixing; these B-CHE models achieve extremely compact structures, maintaining core rotation rates ($\omega_c$) and $T/|W|$ ratios nearly an order of magnitude higher than single-star baselines. Conversely, for accretors that follow standard evolution (B-Std) and retain a hydrogen envelope, we demonstrate that a subsequent Common Envelope (CE) phase can rescue their angular momentum. If the post-CE stripped star enters a tight orbit ($P_\mathrm{CE} \le 0.5$ days) with a companion, robust tidal synchronization can spin up the core to rotation rates that rival or even exceed those of the CHE models. Ultimately, our results highlight that binary interactions—through either mass-accretion-induced CHE or post-CE tidal locking—are highly effective and necessary channels for producing the fast-rotating cores.

Speaker: Yo-Yo Chu

ASROC_YoYo.pdf

12 Exploring the spectral characteristics of Type Ia supernovae and their relationship with host galaxies

The progenitor systems and explosion mechanisms of Type Ia supernovae (SNe Ia) are not yet fully understood. We aim to constrain them by analyzing the properties of their host galaxies, from which we can infer key information about the progenitors. In this study, we analyze the maximum light spectra of SNe Ia using data from ePESSTO+ from 2019 to 2023. We investigate the relationship between the SN ejecta velocities and pseudo-equivalent widths (pEW) of the Si II λ6355 and Si II λ5972 absorption lines and the physical properties of their host galaxies, including stellar mass, star formation rate, and specific star formation rate. We test how different SN Ia classification schemes correlate with their host galaxy environments. Our results show that the conventional subtype classification provides the clearest distinctions among host properties. Furthermore, High-velocity (HV) events correlate with host properties suggestive of sub-Chandrasekhar mass explosions, whereas Normal-velocity (NV) events likely arise from multiple channels. For these subtypes, the pEW of the Si II λ6355 line appears to be a more effective indicator than its velocity for distinguishing between their explosion mechanisms.

Speaker: Cheng-Han Lai (Institute of Astronomy, National Central University)

13 Probing unburned Carbon in White Dwarf Explosions: SN 2022xlp in the Context of Thermonuclear Supernovae

The community has reached a consensus that thermonuclear supernovae are explosions of white dwarfs. But it is not known how an isolated white dwarf can explode. Most explosion scenarios involve white dwarfs in a binary to explain thermonuclear explosions. But the exact nature of the companion star, and the explosion mechanisms are not well understood. White dwarf supernovae are also important source of Fe group elements, so it is important to study their impact on galactic chemical evolution.
Observational campaigns over the years have strengthened the need for invoking multiple progenitor scenarios. This lack of understanding impacts their use as standardizable candles.  We present a detailed case study of SN 2022xlp, a low-luminosity Type Ia supernova exhibiting prominent carbon features at early phases. Our analysis includes optical light curves and spectroscopic observations. The observed properties, supported by spectroscopic modeling, are consistent with an explosion of a carbon–oxygen white dwarf. We compare SN 2022xlp with other thermonuclear supernovae, particularly the 2002cx-like (Type Iax) subclass, to place it in the broader context of SN Ia diversity. 2002cx-like supernovae are crucial for understanding the diversity of thermonuclear explosions, as they likely arise from failed or partial deflagrations and provide key constraints on progenitor systems and explosion physics.

A key focus of this work is the carbon feature at $\lambda6580$, located adjacent to the Si,{\sc ii} $\lambda6355$ doublet. In normal and high-velocity SNe Ia, these features are often blended, complicating their interpretation. However, the relatively low expansion velocities in SN 2022xlp result in less blended spectral features, providing a unique opportunity to probe the presence and role of unburned carbon. Furthermore, we investigate the ionization states across a sample of SNe Ia and find that their wide luminosity range leads to significant differences in ionization and excitation conditions. We would discuss the connections of the plasma conditions to the progenitor scenario.

Speaker: Anirban Dutta (National Central University)

14 Tracing Progenitor and Explosion Properties of Type Ia Supernovae with Swift Ultraviolet Spectra

We investigate the ultraviolet (UV) spectral properties of a large sample of Type Ia supernovae (SNe~Ia) observed with the {\it Swift} UltraViolet and Optical Telescope (UVOT) grism. This sample is much larger than our previous works and includes more early-time UV spectra. We investigate how the UV emission relates to $\Delta m_{15}(B)$, host-galaxy properties, and ejecta characteristics. We recover the previously reported correlation between UV flux levels and $\Delta m_{15}(B)$ at near-peak phase, and find the relation to also hold at early times. In contrast, we do not confirm earlier claims of a metallicity dependence at near-peak and find only a weak trend at early times, with no significant correlations observed with other global host-galaxy parameters such as stellar mass, age, star-formation rate, and specific star-formation rate. The UV properties show a strong connection with ejecta properties such as the pseudo-equivalent width of \si\ at both early and near-peak phases, while only a weak association with \si\ ejecta velocity at early times. Furthermore, we investigate SNe~Ia exhibiting early-time photometric excesses and find no corresponding enhancement in their UV spectra, suggesting that these excesses are unlikely to be driven by circumstellar interactions. Finally, we compare the UV spectra of several SNe~Ia subtypes and find distinct UV signatures, consistent with their optical properties. These results indicate that the UV diversity of SNe~Ia is primarily driven by explosion and ejecta properties rather than by their global host-galaxy environment. The UV spectra used in this work are publicly available on \texttt{GitHub}.

Speaker: Snehasish Bhattacharjee (National Central University)

Welcome reception

Sat, May 16

Plenary talk: Investigations for Historical Archival Records and Reconstructions of Centennial Solar Activity

Convener: Hao-Yuan Duan

15 Investigations for Historical Archival Records and Reconstructions of Centennial Solar Activity

The solar activity shows not only regular Schwabe cycles every ≈ 11 years but also some long-term variations and secular trends. Among them, we have some extreme cases such as the Maunder Minimum. Such long-term modulations are challenging to capture or analyse, as the space-borne measurements and most of the ground-based observations cover only decades. The scientific community can resolve such difficulties using historical records, especially those for sunspot observations and eclipse observations, as they offer data in centennial timescales. However, the existing reconstructions conflict each other before 1900. Here, we explore several case studies for reconstructions of the past solar activity, putting foci on the major fault lines of the sunspot number recalibrations, namely the Dalton Minimum, the Maunder Minimum, and their neighborhood. We have substantial developments in this field all the way back to 1607 by instrumental sunspot observations and back to -708 by historical eclipse observations. These records allow us to contrast the Maunder Minimum with its aftermath and the Dalton Minimum, emphasizing how peculiar the Maunder Minimum was.

Speaker: Prof. Hisashi Hayakawa (Nagoya University)

Coffee break, group photo, poster session

Compact objects and high-energy astrophysics

Convener: Hsiang-Yi Karen Yang (National Tsing Hua University)

16 A Confirmed Supernova Remnant and a Possible Neutron Star in the Main Body of 30 Doradus

30 Doradus is one of the most active star-forming regions. In its main body, confirming supernova remnants (SNRs) remains challenging due to the highly ionized environment, strong thermal emission, and diluted optical shock diagnostics.

In this work, we present compelling multiwavelength evidence for an SNR located in Shell 1 within the main body of 30 Dor A, based on archival observations from HST, CTIO, Spitzer, Chandra, MeerKAT, and ASKAP.

We identify several key SNR signatures, including diffuse X-ray emission, nonthermal radio emission with a spectral index of $\alpha \approx -0.64$, localized enhancements of the [SII]/H$\alpha$ ratio, and high-velocity features in the H$\alpha$ line revealed by high-dispersion echelle spectroscopy. Taken together, these diagnostics strongly support the presence of an SNR embedded in a highly photoionized environment, where traditional criteria alone may fail.

By examining the underlying massive stellar population, we further constrain the properties of the supernova progenitor and identify a bright X-ray point source, CX15, consistent with a neutron star or pulsar candidate.

Our results demonstrate that multiwavelength analysis is essential for identifying SNRs in extreme environments such as 30 Dor, and provide new insights into supernova activity in giant HII regions.

Speaker: Kai-I Cheng (NTU/ASIAA)

17 3D Global Relativistic Radiation Magnetohydrodynamics of Magnetically Arrested Disk Accretion Flows in AGNs

We carry out three-dimensional radiation-relativistic magnetohydrodynamic (3D Rad-RMHD) simulations of accretion flows around spinning active galactic nuclei (AGNs). Our study focuses on the magnetically arrested disk (MAD) state, utilizing a single-temperature model that incorporates bremsstrahlung opacity as the sole radiation process while varying the black hole spin from non-spinning to rapidly spinning cases. Our findings indicate that the MAD state persists across all spin values, as evidenced by the normalized magnetic flux at the event horizon and the spatially averaged plasma beta. The overall flow dynamics remain qualitatively similar for all spin models in 3D simulations, suggesting that black hole spin has minimal impact on the accretion dynamics. Additionally, we conduct post-processing using a two-temperature model to calculate the luminosities from synchrotron and bremsstrahlung radiation. We discover that the total radiation luminosity is significantly higher than the luminosities from either synchrotron or bremsstrahlung alone. This result emphasizes the role of radiation in influencing the dynamics of the accretion flow. Our analysis reveals that the electron temperature is notably high in the jet region, regardless of the spin value. Furthermore, we observe that the temporal evolution of both radiative and synchrotron luminosities exhibits qualitatively similar behavior across all spin values. In conclusion, our results suggest that black hole spin has a minimal effect on the spectral energy distribution (SED) in MAD state accretion flows.

Speaker: Mohammed Ramiz Aktar (Institute of Astronomy, National Tsing Hua University)

18 Simulations of images of accretion discs around Kerr black holes relevant to M87∗

Supermassive black holes (SMBHs) like M87∗ and Sgr A∗ have been observed with the Event Horizon Telescope (EHT), facilitating the investigation of null geodesics near a black hole. The null geodesic around black holes and relevant features such as photon ring, lensing ring and black hole shadow, have been modelled analytically. The emission and absorption of plasmas surrounding a black hole is highly related to the physical quantities such as mass density, momentum, internal energy, magnetic field, black hole spin, and angular momentum. The images of accretion discs around black holes are affected by Doppler shift, gravitational redshift, and frequency-dependent emissivity and absorption coefficient, which can be assessed by numerical simulations. In this work, a numerical ray-tracing scheme and a covariant radiative transfer scheme are proposed to simulate the photon trajectories emitting from the accretion discs around Kerr black holes, hence to reconstruct their images. A set of magnetized, geometrically thick accretion discs are adopted to compute the emissivity and absorption coefficient, which are then used to reconstruct the images of the subject accretion discs. The effects of magnetization, black hole spin, angular momentum and geometry of the discs are studied. The effects of Doppler shift, gravitational lensing, and frequency-dependent emissivity and absorption coefficient are investigated by simulations.

Speaker: Dr Che-Jui Chang (National Taiwan University)

19 Unsupervised Classification of M87* Polarization Images via Autoencoders

Polarized emission from the vicinity of black hole systems carries essential information about local magnetic field configurations in the strong gravity regime. In this work, we employ unsupervised learning to a library of model GRMHD Stokes images of M87*, cluster the images based on the polarized image features, and explore how the clustering depends on the model parameters such as black hole spin, accretion type, and electron energies. To perform the clustering, we apply an autoencoder for dimension reduction of the image library, and group the resulting distributions in the latent space with k-mean clustering. The clustering results depend on whether the polarized properties are included in the channel of the input data, implying how the information of model parameters are embedded in different polarized properties.

Speaker: Chieh-Yu Kuo (NTNU)

20 Equatorially Asymmetric Magnetic Fields and Their Impact on Black Hole Accretion Dynamics

We investigate the impact of equatorial asymmetry in the magnetic field geometry on accretion dynamics around a spinning black hole using axisymmetric general relativistic magnetohydrodynamic simulations. We consider a Fishbone--Moncrief torus orbiting a Kerr black hole with spin parameter $a = 0.9375$, threaded by large-scale magnetic fields that are asymmetric about the equatorial plane. The degree of equatorial asymmetry in the magnetic field is parametrized by an angle, with values of $30^\circ$, $45^\circ$, and $60^\circ$. We examine how this equatorially asymmetric initial magnetic field configuration influences the magnetic field structure, accretion flow morphology, and angular momentum transport across a range of initial plasma beta values ($\beta = 0.007, 0.005, 0.001$). We find that such deformation in the magnetic field leads to noticeable changes in the inner disk structure, asymmetric outflow patterns in the poloidal plane, and time-dependent variations in accretion rates. These effects are generally more pronounced at lower beta values, where magnetic pressure dominates; in particular, the $30^\circ$ case at $\beta = 0.001$ exhibits strong and persistent asymmetric inflows and outflows. Our results demonstrate that equatorially asymmetric magnetic field configurations can significantly influence the structure and variability of relativistic accretion flows. These findings motivate future extensions to full three-dimensional studies, where black hole magnetosphere can be explored in a more general setting.

Speaker: Ishika Palit (National Tsing Hua University)

Galaxies

Convener: Tetsuya Hashimoto (National Chung Hsing University)

21 Estimating the number density of ORCs in the AGN scenario

This study investigates the origin of Odd Radio Circles (ORCs) by modeling them as remnants of active galactic nucleus (AGN) feedback using the JET semi-analytical framework. Motivated by observed host galaxy properties and recent simulations suggesting that ORCs represent relics of AGN activity following a phase of rapid supermassive black hole (SMBH) growth, we identify candidate hosts with stellar masses of 10^11-10^11.5 M_⊙ and black hole masses of 10^7.5-10^8.7 M_⊙ in a radiatively inefficient accretion state. By applying the Sheth-Tormen halo mass function, we calculate predicted numbers as a function of redshift, finding a stable distribution within 10^12-10^13 M_⊙ halos for 1 ≤ z ≤ 3. Crucially, the model yields predicted number densities at z < 1 that are of the same order of magnitude as observed counts and recent estimates (de Gasperin et al. 2026), with predicted numbers as a function of redshift providing a predictive roadmap for future deep-field radio surveys. These findings strongly support the hypothesis that ORCs are long-lived remnants of powerful AGN jets.

Speaker: Guan-Hong Li (National Tsing Hua University)

22 Early-Time Asymmetry in AGN-Driven Outflows: Insights from SRHD Simulations and Synthetic Spectra

Active galactic nucleus (AGN) feedback drives powerful outflows that play a crucial role in galaxy evolution. The physical origin of asymmetric outflow structures seen in observations remains unclear, as such asymmetries are often attributed to dust obscuration rather than being intrinsically produced. Recent infrared observations with JWST of NGC 7469, however, reveal intrinsically asymmetric outflows, suggesting a physical origin beyond simple obscuration. We perform three-dimensional special relativistic hydrodynamic (SRHD) simulations to study the interaction between an AGN wind and a clumpy galactic disk interstellar medium (ISM). At early times ($\sim 0.1\,\mathrm{Myr}$), the wind--disk interaction naturally produces strongly asymmetric bipolar outflows, with one side reaching velocities of $\sim 2000\,\mathrm{km\,s^{-1}}$ while the other is suppressed by dense gas. Using TRIDENT, a post-processing tool that generates synthetic spectra from hydrodynamic simulations, we generate synthetic spectra of the high-ionization [Ne~V] $24.3\,\mu\mathrm{m}$ line and find that the asymmetry leads to skewed line profiles and preferential blueshifted components. These results demonstrate that environmental interaction alone can explain observed one-sided outflows, providing a direct link between SRHD simulations and high-ionization spectral observations.

Speaker: Chiung-Yin Chang (National Tsing Hua University, Institute of Astronomy)

23 Spatially-Resolved Metallicity of Six Fast Radio Burst Host Galaxies with VLT/MUSE IFU: Probing Their Local and Global Environments

Fast radio bursts (FRBs) are millisecond-duration radio transients whose physical origin remains unknown. Different progenitor channels are expected to arise in distinct host-galaxy environments. However, most previous studies have been limited to analyses of entire host galaxies rather than the immediate environments of FRB sites. Spatially resolved studies are therefore essential for placing direct constraints on progenitor environments. Among the environmental properties, metallicity is particularly important because it governs the stellar evolution of progenitor systems. In this project, we investigate the gas-phase metallicity of six localized FRB host galaxies using optical integral-field spectroscopic data obtained with the Multi Unit Spectroscopic Explorer (MUSE) mounted on the Very Large Telescope (VLT). The sample is selected based on the availability of suitable MUSE observations, and sufficient localization accuracy and reliable spatial association between the FRB position and its host galaxy. We measure key nebular emission lines, including Hβ, [O III] λ5007, Hα, and [N II] λ6584, and estimate metallicities using the O3N2 index. While previous studies have mainly focused on global metallicity, this project will provide the first systematic investigation of local metallicity at FRB sites. By comparing the global and local metallicities of the host galaxies, this study will provide a more direct probe of the immediate FRB environments, test whether FRBs preferentially occur in chemically distinct regions within their hosts, and place tighter constraints on their progenitor populations.

Speaker: Jie Shiuan Gong

24 The first study of local star-formation history in fast radio bursts host galaxies.

Fast Radio Bursts (FRBs) are energetic, millisecond radio signals from cosmological distances. The nature of FRBs, especially their short duration, leads to a lack of well-localized FRBs, being the major challenge for studies on FRB progenitors. The key measurement is the delay time between FRB emergence and past star formation in their host galaxy, called the delay time distribution (DTD). DTD significantly depends on the progenitor types (young/old or single/binary systems). Therefore, it allows us to constrain the FRB progenitor. However, previous studies are limited to the DTD measurements for the entire host galaxies, which are less sensitive to the true delay time at the locations of FRBs, and thus cannot effectively narrow down the possibility of the progenitor type. In our study, we focus on the local star formation history (SFH) and provide DTD at the exact sites of FRBs for the first time. We used archive data of the optical integral field spectrograph, VLT/MUSE, for 6 FRB host galaxies. We conducted spectral energy distribution fitting for the host galaxies and FRB sites with pPXF. For several FRBs’ locations, we found stellar components that are distinct from the global environment. We will discuss case-by-case scenarios and the statistical comparison between FRB sites and the global region.

Speaker: CHUAN-KENG CHUANG

25 Testing the Satellite Origin of Mg II Absorbers around Massive Galaxies

The physical origins of the cool gas traced by Mg II absorption lines around massive galaxies remain an open question. Previous studies have suggested that the cool gas around luminous red galaxies (LRGs) may be associated with their satellite galaxies. In this talk, I will present our effort to test this scenario. We use the largest sample of LRG–QSO pairs from the Dark Energy Spectroscopic Instrument (DESI) and perform cross-correlation measurements to probe the satellite galaxy distribution around LRGs with and without detected Mg II absorption. These measurements allow us to examine whether the detection of Mg II absorption correlates with the presence of satellite galaxies in the vicinity of the sightline, shedding light on the origins of cool gas around massive galaxies.

Speaker: Yu-Ling Chang

Stars and star formation

Convener: Ruolan Jin (National Taitung University)

26 Turbulence and star formation in M33

Understanding the turbulent structure of molecular clouds is essential for linking galactic environment to the regulation of star formation. While the turbulent properties of Galactic molecular clouds have been extensively investigated, direct observational constraints on turbulence modes in external galaxies remain limited.

In this work, we apply the statistical framework developed by Brunt and Federrath to quantify the relative fraction of solenoidal and compressive turbulent motions within a sample of 128 $^{13}$CO(2-1) molecular clouds in the nearby spiral galaxy M33. We measure the relative fraction of turbulent power contained in solenoidal modes (the solenoidal fraction, $R$) and investigate its variation with galactocentric distance, spiral structure, and tracers of recent star formation.

The solenoidal fraction spans $R \approx 0.05$-$0.8$, with mean and median values of $R \approx 0.29$ and $0.23$, respectively. The distribution is systematically shifted toward lower values compared to Galactic measurements obtained using the same methodology, indicating that compressive motions dominate the turbulent energy budget of M33 molecular clouds. The solenoidal fraction exhibits modest but systematic radial variations, with a minimum at $R_{\rm gal} \sim 2$-$4$~kpc, but shows no clear association with spiral arms or far-infrared tracers of recent star formation.

These results suggest that, while the balance between compressive and solenoidal modes varies weakly across the disk, the turbulent structure of molecular clouds is largely decoupled from large-scale galactic features and instead evolves primarily under local cloud-scale processes.

This work represents the first application of the Brunt \& Federrath statistical framework to molecular clouds in an external galaxy, demonstrating that turbulence mode analysis can now be extended beyond the Milky Way using spectroscopic data alone.

Speaker: Raffaele Rani (NTHU)

27 Chemistry in the turbulent interstellar medium

Chemistry in the interstellar medium (ISM) is the crucial link between theory and observations. While hydrodynamical simulations are the standard for forward modeling, they often lack the resolution to capture essential small-scale processes. In this talk, I will demonstrate that even in cutting-edge, high-resolution simulations (on parsec scales), sub-grid clumping remains a critical missing piece. Moreover, I will discuss the limitations of the traditional clumping factors and present a novel sub-grid model that accounts for the competition between turbulent mixing and chemical reactions.

Speaker: Chia-Yu Hu (Institute of Astrophysics, National Taiwan University)

28 Simulating the Dynamical Evolution of Globular Clusters in a Galactic Environment

The evolution of globular clusters is an important topic in astronomy.
Observational results suggested that the external tidal field will
affect the evolution of globular clusters significantly. Therefore, we
use the method of N-body simulations to investigate how various physical
parameters of a globular cluster—such as total mass, half-mass radius,
concentration parameter, and truncation parameter—
evolve over time under different external tidal fields.

Speaker: Yu-Hao Yao

29 Thermochemical models of embedded disks in the era of JWST, ELT/METIS, and PRIMA

Planets form within protoplanetary disks; therefore, understanding the diversity of planetary compositions requires studying how material is distributed and evolves within these disks. During their first million years, young disks remain embedded in the envelopes of natal molecular clouds and continue to accrete material. This accreting material alters the disk’s physical and thermal structure and undergoes chemical processing as environmental conditions change. With recent evidence suggesting that planet formation may begin during this embedded stage, it becomes essential to characterize the physical and chemical evolution of such systems. Current and upcoming facilities like JWST (James Webb Space Telescope), ELT/METIS (Extremely Large Telescope/Mid-infrared ELT Imager and Spectrograph), and PRIMA (PRobe far-Infrared Mission for Astrophysics) offer unprecedented spectral and spatial resolution at infrared wavelengths, providing new opportunities to probe planet-forming regions in embedded disks. To complement these observations, we develop a grid of 2D thermo-chemical models incorporating both disk and envelope components using the DALI (Dust And LIne) code. We focus on the dominant physical and chemical processes governing the distribution and evolution of material in embedded disks. We will present the initial results from the study and discuss the evolution of the physical-chemical structure of the disk during its embedded phase.

Speaker: MIHIRKUMAR SANJEEVKUMAR TRIPATHI (National Tsing Hua University)

30 How azimuthal accretion flows can affect dust growth via streaming instabilities

The streaming instability (SI) is a key mechanism for forming kilometer-sized planetesimals from dust or pebbles in the core accretion scenario of planet formation. In disks with a radial pressure gradient, the SI can locally enhance the dust-to-gas ratio, leading to gravitational collapse and helping to overcome both collisional and radial drift barriers. Recent studies have identified a new variant, the azimuthal-drift streaming instability (AdSI), which is driven by azimuthal accretion flows and can operate even in the absence of a radial pressure gradient.
In this study, we perform hydrodynamic simulations using an axisymmetric shearing box to investigate dust growth efficiency under varying strengths of azimuthal accretion flow. Our results suggest that in the non-clumping regime of the classical SI, azimuthal accretion flow enhances dust growth efficiency. In contrast, in the clumping regime, azimuthal accretion flow stabilizes the SI, thereby reducing growth efficiency.

Speaker: Shiang-Chih Wang (National Tsing Hua University/ ASIAA)

Lunch

Compact objects and high-energy astrophysics

Convener: YI CHOU (Graduate Institute of Astronomy, NCU)

31 Drivers of Black Hole Accretion in JWST Galaxies Across 0 < z < 17

We investigate the physical drivers of active galactic nucleus (AGN) luminosity and its connection to host galaxy evolution across cosmic time using a multi-wavelength dataset from the \textit{James Webb Space Telescope} (JWST) SMILES and JADES surveys. Our sample consists of 2,735 galaxies spanning lookback times from 0.8 to 13.6 Gyr ($z \gtrsim 0$--17), with robust spectral energy distribution (SED) fitting performed using \texttt{CIGALE} to derive key physical properties, including stellar mass, star formation rate (SFR), dust luminosity, stellar age, and AGN contribution ($frac_{\rm AGN}$).
We perform correlation analysis and principal component analysis (PCA) to identify the dominant factors governing AGN activity. We find that AGN luminosity ($\log L_{\rm AGN}$) correlates strongly with recent star-forming activity ($\log \mathrm{SFR}_{10\,\mathrm{Myr}}$) and dust luminosity ($\log L_{\rm dust}$), indicating a shared dependence on cold gas reservoirs. In contrast, stellar age and star formation history (SFH) duration show moderate negative correlations, suggesting that AGN activity preferentially occurs in younger systems. Stellar mass exhibits a secondary positive correlation, acting as a scaling factor rather than a primary driver.
PCA reveals that the majority of variance ($>90\%$) is captured by two components: an activity/scale axis linking AGN power, SFR, and dust emission, and an evolution axis tracing stellar age. We identify a peak in the dominance of the activity axis at intermediate redshifts, where galaxy mass and energetic output are most tightly coupled. At higher redshifts, AGN accretion, star formation, and dust heating become increasingly synchronized, reflecting gas-rich conditions in the early universe.
Our results demonstrate that AGN luminosity is primarily governed by the host galaxy's current gas supply and recent star formation, with galaxy mass setting the overall potential. This highlights a co-evolution scenario in which black hole growth and star formation are tightly linked, particularly at early cosmic epochs.

Speaker: Priyanka Jalan (Institute of Astronomy, National Tsing Hua University)

32 Multi-wavelength Observations of a Long-term Monitored Hyperluminous X-ray Source: An AGN-like IMBH or a Low-mass SMBH

Identifying intermediate-mass black holes (IMBHs) is crucial for understanding the co-evolution of galaxies and the seeds of supermassive black holes. We present a comprehensive multi-wavelength analysis of IC 1633 X-4 (2CXO J010952.3-455526), a hyperluminous X-ray source projected at the outskirts of the galaxy IC 1633 (z $\approx$ 0.024). By combining optical photometry from HST/WFPC2 with multi-epoch X-ray observations from Chandra, XMM-Newton, and Swift/XRT, along with UV coverage from Swift/UVOT to GALEX, we constructed a detailed broadband spectral energy distribution (SED).
We studied the interaction between the accretion disk and the X-ray corona using an irradiated disk model that incorporates both Galactic and intrinsic reddening. Our SED fitting yields a bolometric luminosity of $L_{bol} \approx 3.54 \times 10^{42}$ erg s$^{-1}$ and $\log(f_X/f_{opt}) = -0.25$. These results are remarkably consistent with the properties of standard active galactic nuclei (AGN), suggesting that the source operates in a similar accretion regime.
Most notably, the best-fit model reveals a low disk temperature of $kT_{bb} \approx 41$eV and an X-ray photon index of $\Gamma \approx 2$. Combined with the measured $L_{bol}$, it provides evidence for a black hole mass in the range of $10^4 - 10^6 M_\odot$, assuming sub-Eddington to near-Eddington accretion rates. Our findings indicate that IC 1633 X-4 is either a viable IMBH candidate, exhibiting AGN-like physics scaled down to the intermediate-mass regime, or a low-mass SMBH operating at a relatively low accretion rate.

Speaker: Yi-Chi Chang (Institute of Astronomy, National Tsing Hua University, Hsinchu 30013, Taiwan)

33 Properties of GS 1354-64 During its Recent 2025-26 Outburst

GS 1354-64 is a dynamically confirmed Galactic transient black hole. Recently, it exhibited a bright outburst. We study the temporal, spectral, and polarimetric properties of the source using multi-satellite data. The outburst consists of two short-duration ($\sim 3$-$5$ days) bright X-ray flares, with peak fluxes of 1.4 and 0.8 Crab, respectively. The source exhibits strong signatures of quasi-periodic oscillations (QPOs) and their evolution. The propagating oscillatory shock (POS) model successfully fits the monotonic evolution of the QPO frequency. This provides a clearer understanding of the evolution of the shock wave responsible for the origin of the observed QPOs. A strong signature of relativistic reflection is also observed. From spectral analysis using the relativistic reflection model {\tt RELXILL}, the black hole spin and inclination angle are estimated to be $a = 0.997 \pm 0.002$ and $i \sim (61$--$71)^\circ$, respectively. Strong polarization is detected, with a polarization degree (PD) of $4.1 \pm 0.45$ % ($\sim 10\sigma$ confidence) and a polarization angle (PA) of $(-2.31 \pm 2.8)^\circ$ in the IXPE energy band of $2$-$8$ keV. Both PD and PA are also found to evolve with energy. Detailed spectral analysis suggests that the source was in the softest spectral state during both flares.

Speaker: Dipak Debnath (National Tsing Hua University)

34 Investigating the nature of magnetic turbulence in Tycho’s SNR using X-ray observation

Supernova remnants (SNRs) are widely regarded as the primary sources of Galactic cosmic rays, with particles accelerated at their shock fronts through the diffusive shock acceleration (DSA) mechanism, gaining energy via repeated shock crossings. Magnetic turbulence plays a crucial role in scattering these particles, making its characterization essential for understanding the acceleration process. In this study, we apply the two-point correlation method to derive the magnetic energy spectrum from the non-thermal X-ray flux image of Tycho’s SNR. The non-thermal flux image is obtained using Poissonian-based Generalized Morphological Component Analysis (pGMCA). The turbulence length scale inferred from the resulting magnetic energy spectrum is smaller than that derived from previous radio studies of Tycho’s SNR. Additionally, we estimate the magnetic energy spectrum using the X-ray rim thickness measured across the remnant, which serves as a proxy for the magnetic field strength. The turbulence scale derived from this approach is consistent with the magnetic energy spectrum obtained from the non-thermal X-ray flux analysis.

Speaker: Ashwin Aravindaraj (Institute of Astronomy, National Tsing Hua University)

35 Broadband Spectral and Timing Study of GX 9+9 Using Multi-mission Observations

We present a comprehensive broadband spectral and timing study of the bright atoll neutron star low-mass X-ray binary GX~9+9 using two simultaneous NICER, NuSTAR, and MAXI observations obtained in 2019 and 2022. During both epochs, the source resides in the lower banana branch of the color–color diagram, consistent with a soft spectral state. The broadband spectra in the $0.7-40$ keV band are adequately described by a combination of multicolor disk emission, thermal Comptonization of blackbody seed photons originating from the neutron star surface, and disk reflection. We employ both phenomenological and physical models, including blurred reflection models \texttt{relxillCp} and \texttt{relxillNs}, and find that both frameworks adequately describe the reflection features, including a prominent narrow Fe K emission line present in both observations. However, the reflection hump is found to be relatively stronger in the 2022 epoch. Our spectral analysis reveals clear evidence of spectral evolution between the two observations. The spectrum obtained from the 2022 observation shows a steeper Comptonized component, characterized by a lower optical depth, along with an increase in both the inner disk temperature and the seed blackbody temperature. Despite the soft spectral state, reflection modeling indicates a substantially truncated inner accretion disk in both epochs, while thermal Comptonization strongly dominates the overall source flux. Independent constraints from disk continuum modeling also support this truncated geometry, with a modest inward shift of the disk in 2022. The inferred reflection fraction in terms of the solid angle subtended by the reflector appears to be consistent with the truncated disk scenario. Timing analysis shows that the variability is dominated by the Comptonized component, while the disk remains relatively stable. We detect significant soft (negative) lags at high frequencies, which may be associated with thermal reprocessing of hard X-rays in a truncated accretion disk. The lag–energy spectra exhibit structured features, with deviations around the Fe K band, indicative of Fe K reverberation.

Speaker: Dr Swadesh Chand (Postdoc, Institute of Astronomy, National Tsing Hua University)

36 Phase-Resolved X-ray Spectral Evolution of the Radio Magnetar XTE J1810-197

Radio emission from magnetars is closely linked to their X-ray activity, yet the connection remains complex. Radio emission is typically observed during and after X-ray outbursts, exhibiting highly variable flux evolution, in contrast to the more monotonic decay seen in X-rays. In this paper, we present a phase-resolved X-ray spectroscopic analysis of the 2018 outburst of XTE J1810−197. Pulse phases are defined using both X-ray and radio pulse profiles to enable a direct comparison between the two emission regimes. We model the phase-resolved spectra using blackbody, power-law, or their combination. In addition, we investigate the evolution of the components in the X-ray pulse profile. These results are then compared with the radio evolution reported in the literature. We find that most spectra require two-component models to achieve acceptable fits, while some phases at certain epochs can be well described by a single-component model. However, neither the spectral parameters nor the epochs where single-component models are sufficient show a clear evolutionary correlation with the radio behavior, despite the complex variability seen in the radio emission. This study provides new insights into the phase-dependent coupling between X-ray and radio emission processes in magnetars and helps constrain the multiwavelength behavior.

Speaker: Che-Yen Chu (National Changhua University of Education)

37 A cosipy Pipeline for Pulsar Timing and Phase Resolved Spectroscopy with COSI

Pulsars are critical laboratories for studying extreme particle acceleration, with the Crab pulsar serving as a benchmark across the electromagnetic spectrum. Observations in the MeV gamma-ray band ($0.2–5$ MeV) are essential for probing the spectral turnover where emission mechanisms transition. The upcoming Compton Spectrometer and Imager (COSI) will provide sensitive measurements in this regime; however, analyzing pulsar data with a Compton telescope requires managing large datasets and complex phase-resolved selection. We present a streamlined, high-performance framework developed using vectorized NumPy-based algorithms to facilitate phase-resolved studies using simulated COSI data.Our framework consists of a specialized suite designed for the rapid processing of MEGAlib simulated event files. It features a frequency-based PhaseAssigner for efficient pulsar folding and a robust PhaseSelector capable of handling multiple, simultaneous phase intervals to isolate specific components of the pulse profile. To validate detection significance, we implement a cumulative $Z^2_2$ statistic diagnostic, enabling real-time monitoring of signal growth over the observation duration. By applying this framework to the Crab pulsar as a test case, we demonstrate the construction of high-resolution pulse profiles and the effective separation of pulsed emission from steady-state nebular components. This methodology establishes a scalable foundation for future COSI pulsar analyses, highlighting the mission's potential to advance our understanding of magnetospheric emission physics through optimized, large-scale event processing.

Speaker: Koothodil Abhijith Augustine (Institute of Astronomy, National Tsing Hua University, Hsinchu)

Galaxies

Convener: Hung-Yi Pu (National Taiwan Normal University)

38 Constraining the X-ray Count Rate-Mass Scaling Relation of RASS Clusters in a Joint Analysis of Halo Clustering and Weak Lensing

We constrain the X-ray count rate-mass relation of 7408 RASS X-ray selected galaxy clusters at $0.05 < z < 1$. The sample is further optically confirmed based on the optical imaging from Legacy Survey DR9 and DR10, leading to a sample purity at $90\%$. We measure the weak-lensing shear profiles using the Hyper Suprime-Cam (HSC) Y3 data set, resulting in a total signal-to-noise ratio of $30.9$. Meanwhile, we measure  the auto correlation of the clusters and the cross-correlation between them and the  Bright Galaxy Survey (BGS) sample from the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1). We model the measurements of the shear profiles and the correlation functions jointly to constrain the X-ray count rate-mass relation. Finally, we compare the results from small-scale weak lensing and the large-scale clustering to assess mass calibration across different scales.

Speaker: I-Hsuan Li (National Cheng Kung University)

39 The Stellar Content of Galaxy Clusters selected in X-rays

We aim to measure the stellar mass content and luminosity function of 6,439 X-ray selected galaxy clusters from the all-sky RASS-MCMF catalog, using WISE W1 (3.4 μm) photometric data. Our sample spans a mass range of $10^{13}M_\odot \lesssim M \lesssim 10^{15}M_\odot$ and redshifts $0.05 <z_{cl}< 0.4$. We use the unWISE catalog with a limiting magnitude of W1 ≈ 20.45 mag.
In our work, we apply corrections for spatial masking and detection incompleteness during the photometric analysis. With these corrections, we measure the luminosity function of these clusters up to the limiting magnitude of the 50% completeness. In addition, we investigate the radial dependence of the luminosity function within galaxy clusters.
We will model the stellar mass content using stellar population synthesis (SPS) models based on the measured luminosity functions.

Speaker: Wen-Chi Hua (National Cheng Kung University)

40 Age Gradients of Post-starburst Galaxies at 1 < z < 1.5 Revealed by JWST

Recent observations with the James Webb Space Telescope (JWST) are revealing an increasing number of quiescent galaxies that had already stopped forming stars when the Universe was only a few billion years old. Given the limited time available for secular evolution at these early epochs, the existence of such quenched systems suggests that their star formation was abruptly shut down. Identifying the physical mechanisms responsible for this early and rapid quenching remains a key challenge in galaxy evolution. Post-starburst galaxies (PSBs), which have shut down their star formation both recently and rapidly, provide a unique opportunity to study these quenching mechanisms.
In this work, we investigate spatially resolved stellar age gradients in a sample of nine PSBs at 1 < z < 1.5 using multi-band JWST and HST imaging. Six PSBs show younger central stellar populations, while three exhibit flat age gradients. Overall, our analysis reveals predominantly younger stellar populations in the central regions of PSBs, consistent with recent centrally concentrated star formation superimposed on an older, more extended stellar component. This results in flat or mildly positive radial age gradients. The observed central starbursts may be driven by dissipative processes such as secular disk instabilities or gas-rich mergers, followed by rapid quenching via disk stabilization or feedback from active galactic nuclei (AGN) and massive stars. Our results support a fast quenching scenario, indicating that multiple mechanisms likely act together to drive the rapid transition from star-forming to quiescent phases in PSBs at this redshift.

Keywords: Post-starburst galaxies (PSBs), Stellar age gradients, Rapid quenching

Speaker: Rajashree Bhuyan (National Taiwan University, Department of Physics)

41 Tracing Obscured AGN Contribution and Number Fraction Across 0 < z < 6 with JWST

Active galactic nuclei (AGN) are pivotal drivers of galaxy evolution, yet many remain undetected in ultraviolet and optical surveys due to heavy dust obscuration. Tracking the AGN infrared (IR) contribution and number fraction (AGN fraction of IR-selected galaxies) provides insight into the dominance of AGN activity within galaxies and how common AGNs are across cosmic time. In these systems, dust absorbs the high-energy accretion disk emission and re-radiates it at longer wavelengths, making mid-IR observations essential for uncovering the full population of obscured AGN. Historically, the AKARI space telescope provided key insights into these populations; however, JWST’s 6.5m mirror offers ∼90 times the sensitivity of AKARI’s 0.68m aperture, allowing for the detection of much fainter objects during early stages of galaxy growth. Utilizing the JWST Systematic Mid-infrared Instrument Legacy Extragalactic Survey (SMILES) and the JWST Advanced Deep Extragalactic Survey (JADES), we leverage continuous optical to mid-IR coverage (5–25 μm) in the GOODS-S field to identify obscured AGN via multi- wavelength SED fitting with CIGALE. Our sample includes 278 AGN across 0 < z < 6, a seven-fold increase over previous JWST Cosmic Evolution Early Release Science (CEERS) survey studies due to the larger 15-pointing SMILES MIRI footprint. We find that both the AGN IR contribution and number fraction increase significantly with redshift, while decreasing as a function of total IR luminosity. This suggests that at higher redshifts, the IR galaxy luminosity is dominated by AGN activity and is primarily driven by abundant gas reservoirs and frequent mergers in the early universe, whereas in the local universe, high IR luminosity is increasingly dominated by intense starburst activity rather than black hole accretion. These results highlight JWST’s capacity to reveal previously hidden populations, suggesting that AGN activity was more prevalent and energetically dominant in the early universe.

Speaker: Angel Rodriguez Barbosa (National Tsing Hua University)

42 Cosmological inference with halo clustering reconstructed from redshift-space galaxy distributions

Accurate modeling of small-scale redshift-space clustering is crucial for full-shape RSD analyses, where satellite galaxies contribute to 1-halo terms and Finger-of-God distortions. We study halo reconstruction with the cylinder-grouping method of Okumura et al. (2017), which selects an effective halo-center tracer from the observed galaxy distribution. Using DESI-like LRG mocks from AbacusSummit $N$-body simulations at $z=1.1$, we perform EFT-based fits to the power-spectrum multipoles within the ShapeFit framework.
We show that the main reconstruction-induced systematics can be consistently handled within the same EFT likelihood. In particular, the dominant large-scale effect is captured by a simple multipole-dependent rescaling measured directly from the data, while residual small-scale changes are absorbed by the standard counterterm and stochastic sectors without introducing reconstruction-specific parameters. Compared to galaxy-based fits, the reconstructed sample yields more stable constraints on all ShapeFit parameters as $k_{\max}$ is increased. In particular, the inferred $f\sigma_8$ remains consistent with the fiducial cosmology beyond $k_{\max}\simeq 0.2\,h\,{\rm Mpc}^{-1}$, where the galaxy-based result begins to drift. At higher $k_{\max}$, reconstruction reduces the $1\sigma$ uncertainty on $f\sigma_8$ by $\gtrsim 20\%$ relative to the galaxy case.

Speaker: Ryuichiro Hada (ASIAA)

43 Galactic Mergers as a Universal‑Scale Astrophysical Resolution of the Fermi Paradox

The Fermi Paradox poses a fundamental question: why, given the immense age and scale of the Universe, have we not observed evidence of advanced civilizations beyond our own? Explanations range from sociological ideas such as the zoo hypothesis to the possibility that advanced civilizations are inherently undetectable. An alternative line of inquiry emphasizes astrophysical causes. Previous studies have shown that hazardous astrophysical events—including asteroids, supernovae (SNe), and giant molecular clouds (GMCs)—can eradicate advanced civilizations within the Milky Way (MW). Among these, asteroids appear to be the most decisive factor. This raises a deeper issue: could civilizations have disappeared even before the MW itself was assembled? The early universe was shaped by frequent galactic mergers, in which smaller systems combined to form larger structures, including our own Galaxy. To investigate this scenario, we simulated the migration and potential extinction of advanced civilizations during a major galactic merger. As a representative case, we examined the predicted future collision between the MW and the Andromeda Galaxy (M31). Preliminary results indicate that such mergers may lead to partial extinction events, driven primarily by the elevated rate of SNe formation. These findings strengthen astrophysical interpretations of the Fermi Paradox, suggesting that the absence of detectable civilizations may be explained by the destructive influence of large‑scale galactic dynamics. In this framework, the absence of observable civilizations is interpreted as a consequence of the inherent fragility of life when subjected to destructive astrophysical events.

Speaker: Mr Deriyan Senjaya (Department of Physics NTHU Taiwan)

44 Measuring dwarf galaxy distances with Surface Brightness Fluctuations in the DESI Legacy Survey

Accurate distance measurements are fundamental to understanding the formation and distribution of galaxies in the nearby universe. For faint and diffuse systems, such as dwarf and low-surface-brightness (LSB) galaxies, distances are needed to distinguish satellites from background systems, to derive physical properties such as mass and size, and to map the structure of the local volume (LV). However, measuring these distances remains challenging. Redshift-based estimates are unreliable due to the local velocity field, while stellar-based methods such as the tip of the red giant branch (TRGB) require resolved imaging that is often unavailable for LSB dwarfs.

The surface brightness fluctuation (SBF) method provides a robust method for measuring distances to dwarf galaxies in the nearby universe. With the advent of deep, wide-field surveys such as the DESI Legacy Imaging Surveys (LS), Euclid, and the upcoming LSST, the SBF method has seen renewed interest as a tool for mapping the nearby dwarf galaxy population.

In this work, we apply and adapt the SBF method to LS imaging. We introduce two key modifications to account for 1) correlated noise and 2) varying point-spread function (PSF) in the coadd images. We demonstrate that reliable SBF distances can be recovered for dwarf galaxies within $\sim10$ Mpc by measuring the SBF of galaxies with known TRGB distances and mock dwarfs injected into LS coadds.

Finally, we perform a systematic search for dwarf galaxies across the LS footprint and aim to build a catalogue of SBF distances. This catalogue will provide new insights into the three-dimensional distribution of satellite and field dwarf galaxies, helping to constrain the large-scale structure and star formation history of the local volume.

Speaker: Tsz Hei Chan (NTHU)

Stars and star formation

Convener: Chin-Fei Lee (ASIAA)

45 Comparison Analysis of gri-Band Period-Luminosity-Metallicity Relations and Host Environment of RR Lyrae

We compared empirical RR Lyrae period-luminosity-metallicity (PLZ) and period-Wesenheit-metallicity (PWZ) relations that were calibrated using various RR Lyrae origins to evaluate the accuracy and validity of distance estimations. Our analysis employs RR Lyrae samples from various host systems, including the Large Magellanic Cloud, Draco dwarf galaxy, and globular cluster $\omega$ Centauri. We evaluated the performances and consistencies of the empirical relations by comparing the relation-inferred distances with distances that were independently measured. Furthermore, we conducted statistical tests to compare the pulsating behaviors and explore the evolutionary effects of each dataset, aiming to explain the RR Lyrae differences in diverse host environments. The comparative analysis may provide a standard to reduce the selection bias in calibrating the PLZ relations and the capabilities of existing gri-band empirical relations

Speaker: Pin-Hsien Lai (Graduate Institute of Astronomy, National Central University)

46 HOPS-288: A Laboratory for Complex Organics in Proto-binary/Proto-multiple Systems

Proto-binary and proto-multiple systems with close separations are particularly valuable targets for investigating chemical inheritance and reaction, as their members are expected to form from similar material in their parental cloud. Complex organic molecules (COMs) in young stellar objects (YSOs) have attracted significant attention due to their potential connection to pre-biotic chemistry and their utility as tracers of warm or shocked gas components. We present ALMA observations of the hierarchical proto-triple system HOPS-288, focusing on the physical structure, kinematics, and COM compositions. The system is treated as a proto-binary system due to the limited spatial resolutions, with a separation of 200 au. Three COM-rich features are revealed: two hot corinos associated with the two members, rich in a variety of COMs, and an intervening component between the two members. One hot corino exhibits rotational features and might trace a disk. The other one is also possibly exhibiting rotational motion. The intervening component could possibly trace a shocked region in the circumbinary disk or a bridge between the two members. The column densities of COMs are broadly similar between the two sources, possibly suggesting the complex organic similarities among proto-binary/multiple systems. Given the complexity of the studied physical structures, further detailed investigations will be essential to confirm this result.

Speaker: Shih-Ying Hsu (ASIAA)

47 Early Planet Formation in Embedded Disks in Ophiuchus (eDisk@Oph): A super-resolution analysis of protostellar disks

Substructures are ubiquitous --- nearly 60\% of protostellar disks, which is less than 1 Myr, host features such as rings/gaps, spirals, and crescents. These features are widely interpreted as evidence for embedded giant planets, suggesting that planet formation occurs much earlier than previously thought. However, previous observations have been biased toward bright, large disks, even though small disks dominate statistically. This prompts the question: `Do small protostellar disks possess substructures in their disks?'

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As an extension of the ALMA Large Program Early Planet Formation in Embedded Disks (eDisk), we are conducting a survey of a homogeneous sample of 25 protostars in the Ophiuchus star-forming region (eDisk@Oph). By focusing on a single star-forming region, rather than combining samples from regions at different distances, we minimize uncertainties and biases arising from variations in sample completeness and environment. In this sub-project, we analyze dust continuum emission of protostellar disks using sparse modeling (SpM). The application of SpM has revealed sharper substructures---such as additional rings, gaps, and spirals---even in compact or marginally resolved disks, demonstrating its capability for super-resolution reconstruction.

\medskip

Our sample comprises 25 protostellar disks, including 11 large (with radii $> 20$ au) and 14 small disks ($< 20$ au). Among large disks, three substructures have been already known. To statistically assess whether the occurrence rates of substructures in small and large protostellar disks differ significantly, we use Fisher’s exact test. If the number of detected substructures in small disks is below 9, the two populations of small and large protostellar disks will be considered statistically consistent at the commonly used significance level of 0.05. Conversely, detecting more than 10 substructures would indicate that the two populations are significantly different. This could imply that planet formation is more efficient in small protostellar disks than in large ones.

\medskip

By applying SpM, the spatial resolution improves to approximately 20 mas (2.8~au), compared to $\sim$100 mas (14 au) obtained with the CLEAN algorithm, the standard image reconstruction method in radio astronomy. As a result, we newly identify three substructures in small disks that are not recovered by CLEAN. We tentatively concluded that the substructures are also a universal characteristic in small protostellar disks. In my talk, I will also present the update in data analysis.

Speaker: Jun Hashimoto

48 Evolution of dust in a protoplanetary disc driven by stellar flybys: implications for the streaming instability

Stellar flybys are a common dynamical process in young stellar clusters and can significantly reshape protoplanetary discs. However, their impact on dust dynamics remains poorly understood, particularly in the weakly coupled regime ($\mathrm{St}≫1$). We present three-dimensional hydrodynamical simulations of parabolic stellar flybys—both coplanar and inclined—interacting with a gaseous and dusty protoplanetary disc. Gas and dust spirals differ in morphology and position, with their offset enhancing dust accumulation measured through the linear growth of the streaming instability. Flybys with mass equal to the central star (1 ${\rm M_{\odot}}$) truncate the disc, producing tightly wound, ring-like spirals that promote dust concentration. By mapping the streaming instability growth rates in the solid abundance-Stokes number space across three evolutionary phases, we find that a low-mass flyby suppresses dust concentration below the critical clumping threshold after periastron and maintains this suppression over time, indicating long-lasting inhibition of dust clumping. An equal-mass flyby raises growth rates well above the threshold, suggesting that such encounters may foster conditions favourable for dust clumping. Flyby-induced spirals play a central role in shaping dust evolution, leading to distinct spatial and temporal behaviours in weakly coupled discs.

Speaker: Wei-Shan Su

49 Assessing the Reliability of the Polarization–Intensity Gradient Method in Realistic Star-Forming Environments

Magnetic fields play a crucial role in the process of star formation and the evolution of collapsing dense cores. However, direct measurements of magnetic field strength from observations remain challenging. The polarization–intensity gradient method is a new approach to estimate the magnetic field strength using polarization angle and intensity gradient, which can provide the map of position-dependent magnetic field strength estimates. In this project, we evaluate the applicability and robustness of this method when applied to realistic observational conditions. We perform synthetic Atacama Large Millimeter/submillimeter Array (ALMA) and James Clerk Maxwell Telescope (JCMT) observations based on RAMSES simulations, and apply the polarization–intensity gradient method to estimate the magnetic field strength. We then compare the derived field strengths with the intrinsic values from the simulation to quantify the associated uncertainties. Furthermore, we discuss the physical conditions and environments of dense cores under which the polarization–intensity gradient method provides reliable estimates. Our results aim to clarify the limitations and applicability of this method in interpreting observations of star-forming regions.

Speaker: Jo-Shui Kao (NTHU/ASIAA)

50 Triggered filament and subsequent star formation in the Perseus Molecular Cloud revealed by Nobeyama 45-m telescope

Filamentary molecular clouds are now recognized as the fundamental structures that set the initial conditions of star formation. However, their formation mechanism remains an open question. Among the proposed scenarios, converging gas flows induced by colliding gas layers have emerged as a compelling candidate (Inoue et al. 2018; Arzoumanian et al. 2018, 2022), yet direct observational constraints on how filament properties—such as column density and line mass—are established are still under debate. Here, we present new observational evidences linking filament formation to colliding gas flows in the Perseus molecular cloud, one of the nearest star-cluster-forming regions at a distance of ~300 pc. Using the Nobeyama 45-m telescope, we performed wide-field observations of $^{12}$CO, $^{13}$CO, and C$^{18}$O toward two subregions of Perseus (NGC 1333: 1 deg. $\times$ 1 deg., IC 348: 45 arcmin $\times$ 20 arcmin), tracing gas over a wide range of densities (10$^2$--10$^5$). We identify two molecular cloud components with a velocity separation of ~5 km s$^{-1}$ in both NGC 1333 and IC 348, as observed in $^{12}$CO and $^{13}$CO. These components are connected in velocity space and exhibit complementary spatial distributions—hallmarks of cloud–cloud collisions (Fukui et al. 2021). The two velocity components are also confirmed in HI data obtained with the Arecibo telescope, suggesting that cloud–cloud collisions over a wide dynamic range are occurring throughout Perseus. In C$^{18}$O, we detect a rich network of filaments (20 in IC 348 and 54 in NGC 1333) with a characteristic width of ~0.1 pc. Strikingly, all filaments with line masses exceeding 100 $M_\odot$ pc$^{-1}$ are confined to regions where the two velocity components overlap. We also find that $^{12}$CO filamentary structure in areas lacking C$^{18}$O detection, and these $^{12}$CO filaments are accompanied by the two HI gas components with column density of $\sim$5$\times$10$^{20}$ cm $^{-2}$ for each. Based on these results, we suggest that a collision between $^{13}$CO-detectable gas forms a multiple network of filaments with large line mass, and a collision between HI gas formed the $^{12}$CO filaments. Hence, the line mass of filaments is likely regulated by the pre-collision gas density. We will further discuss the origin and driving mechanisms of cloud–cloud collisions across the Perseus molecular cloud.

Speaker: Rin Yamada (National Astronomical Observatory of Japan)

51 From Clear to Dusty Fields: A Practical Route to CFHT u-Band Calibration

Accurate u-band photometry in the Galactic plane is challenging because crowding, spatially variable extinction, and filter-system differences can strongly distort the observed stellar locus and complicate direct calibration. In this work, I develop an empirical framework for calibrating and interpreting CFHT u-band observations in heavily reddened fields by linking them to external optical and astrometric constraints. Matched CFHT, Pan-STARRS, and Gaia samples are used to place the data in a common comparison space, while Gaia geometric distances and 3D dust information help trace how extinction reshapes stellar colors along the line of sight. A low-extinction reference field is used to characterize the intrinsic behavior of well-measured stars, and that reference is then transferred to a high-extinction target field to study the resulting color-color distribution in a more controlled way. The approach emphasizes careful stellar selection and robust fitting so that calibration trends can be separated from astrophysical scatter. Beyond the immediate CFHT application, this framework is intended to be flexible and may also serve as a useful starting point for thinking about crowded Milky Way optical datasets in future survey contexts, including Rubin/LSST, where related calibration and interpretation challenges are likely to arise.

Speaker: Atharva Patil (National Central University)

Coffee break and poster session

Compact objects and high-energy astrophysics

Convener: Chin-Ping Hu (National Changhua University of Education)

52 Gamma-ray Transient Monitor (GTM): Feasibility of Spectral Study of the Crab pulsar

We present the assessment of scientific capabilities of the Gamma-ray Transient Monitor (GTM) for observing the Crab pulsar. GTM is the science payload on board FORMOSAT-8B (FS-8B), a remote sensing satellite of Taiwan Space Agency (TASA) to launch in late 2026. Two modules of GTM detectors are mounted on opposite (+y and -y) sides of FS-8B, and each consists of four sensor units comprising Gadolinium Aluminum Gallium Garnet (GAGG) scintillator arrays. The geometry of the sensors enables GTM to cover the whole sky at any time, including the directions occulted by the Earth. GTM is most sensitive in the energy range from 50 keV to 2 MeV.

The Crab is a standard candle in high-energy astrophysics, and has yet to be extensively studied in the MeV energy range. Our goals of the Crab pulsar study using GTM in this window include studying the synchrotron tail emission and monitoring possible flux variations. Through simulations with the Medium-Energy Gamma-ray Astronomy library (MEGAlib) in a high-inclination low-Earth-orbit radiation background, the count rates are estimated to be about 1 cps (pulsed component) and about 300 cps (nebula plus background) in the 50-300 keV range. These results indicate that an observation over 100 ks (~1 week, accounting for duty cycle) can achieve a detection significance exceeding 5σ for the pulsed emission. We also assess the instrument’s ability to perform spectral or even polarimetric analysis. These results highlight the mission’s potential to contribute to long-term monitoring and cross-validation with other observatories, demonstrating the additional scientific value of small telescope platforms.

Speaker: JR-YUE HSIANG

53 Study on GRB Detection Efficiency and Localization Capability of Four CubeSat Instrument Models

This study reports the localization performance and detection efficiency analysis of a compact GRB monitor to fly on a future CubeSat. Our current study involves four model concepts of the instrument. Among them, two consist of four hexagonal CsI(Tl) scintillator detectors of geometric area 12.5 cm$^2$, read out by silicon photomultipliers (SiPM), encased in aluminum of 2-mm thickness on the sides, named Model-1 and Model-2, respectively, with Model-1 having one extra square detector of area 8 cm$^2$ on the top. It is to study the performance improvement due to addition of the top detector. Similarly, the other two models have five and four square CsI(Tl) detectors of geometric area 23 cm$^2$ each and they are named Model-3 and Model-4. All detectors have a thickness of 0.8 cm. The base of each instrument has a 3-mm-thick tungsten layer to protect the SiPM from radiation damage. We run simulations with MEGAlib to study the detection efficiency and localization capability of such an instrument and how much the performance can be improved due to the presence of a 5th detector unit. We demonstrate the localization capability of such a 1U-class instrument. Among the four models, the heaviest one, Model-3, can localize a bright GRB (fluence level $7\times 10^{-5} \, \rm {ergs/cm^{2}}$) with a 3$\sigma$ spread of $10^\circ$. When operated in a CubeSat constellation, the arrival time difference method can be employed to further refine the localization.

Speaker: Kaustubha Sen (IoA, NTHU)

54 Rapid Gravitaional Wave Detector Background Estimation using Self-supervised Learning

Estimating the background noise power is essential for gravitational wave (GW) analysis. Typically, people compute the power spectral density (PSD) of the noise background using the Welch method, which is a sliding average over a long period of data, usually spanning tens to thousands of seconds. However, the detector strain data is non-stationary and sometimes glitchy due to the detector's bad status. This can make the estimated noise background not representative of the data we are analyzing. In such cases, people can either manually select a relatively clean segment or use the Monte Carlo method to estimate the noise PSD. Still, the former requires additional manpower for the search, and the latter requires Monte Carlo sampling and is computationally expensive. In this work, we developed a machine-learning method to estimate the PSD from the data we analyzed, without accounting for prior data quality.

Speaker: Yu-Chiung Lin (National Tsing Hua University)

55 Demonstration of Coherence Monitor and Noise Reduction on KAGRA O4a Data

We present an automated noise subtraction pipeline combining Coherence Monitor (CohMon) and DeepClean for KAGRA’s O4a data. CohMon evaluates PEM sensors via frequency-domain coherence to select optimal witness channels. These feed into DeepClean, a 1D CNN, to model and subtract non-linear noise. Applied to O4a strain, it removes artifacts without altering astrophysical signals. Evaluated by ASD ratios, this provides a automated denoising framework for KAGRA.

Speaker: Nim Ki Wong (National Yang Ming Chiao Tung University)

56 Gravitational-Wave Signatures of Fly-by Scatterings from the Kozai-Lidov Effect

ravitational-wave astronomy has provided a unique probe into the dynamics of globular clusters, active galactic nuclei, and few-body gravitationally interacting systems. While binary black hole systems are a prevalent source of gravitational waves in ground-based interferometers, such systems could also be perturbed by the presence of a distant, third body, i.e. a supermassive black hole. Over secular timescales (i.e. timescales larger than the orbital period of the binary), the gravitational interaction of the binary with the third body may lead to orbital resonances. One such resonance, known as the Kozai mechanism, causes an oscillation between the values of the binary’s eccentricity and its inclination with respect to the third body, driving the initially circular binary to arbitrarily high eccentricities at low inclinations. Such eccentricities result in close encounters near periapsis, with GW bursts particularly relevant for ground-based detectors. In this paper, we focus on the Kozai mechanism within the context of gravitational wave astronomy. We use REBOUND, a few-body simulation code, to simulate the dynamics of triple bodies with one steller mass black hole, one intermediate mass black hole, and one supermassive black hole, with kozai oscillations. From the quadrupole formalism, we extract gravitational-wave templates in cases that may be detectable by future detectors, and speculate on the event rate of these kinds of systems.

Speaker: Dr Peter Lott (Phenikaa University)

57 Volumetric rate density of fast radio bursts and its evolution with redshift from CHIME/FRB Catalog 2

Fast Radio Bursts (FRBs) are luminous, coherent radio pulses primarily of extragalactic origin. While a Galactic magnetar has been linked to a few FRB-like events, the progenitors for the vast majority of FRBs remain elusive, largely due to the poor localization capabilities of current FRB instruments. To circumvent this limitation, we employ a statistical approach by investigating the redshift evolution of the FRB volumetric rate density. If FRB progenitors are associated with short-lived star-formation remnants, such as magnetars, their volumetric rate density should track the cosmic star-formation history, increasing toward higher redshifts (z ~ 1-2). In contrast, a nearly constant or decreasing density would suggest an origin in old stellar populations, such as white dwarfs and old neutron stars. While previous studies were limited by small sample sizes (e.g., 164 non-repeaters by Hashimoto et al. 2020), leading to divergent conclusions, this work utilizes 1,077 non-repeaters from the CHIME/FRB Catalog 2. Containing approximately an order of magnitude more non-repeater samples than Catalog 1, this dataset allows for a more robust statistical analysis. We present preliminary results on the volumetric rate density as a function of redshift. The preliminary result suggests a decreasing trend of the volumetric rate density of non-repeaters towards higher redshifts up to z~2, being consistent with the old stellar population scenario. We will also discuss the potential impact of frequency-dependent selection effects on our inference. Significant populations of FRBs at z<0.2 are detected at <600 MHz at the source frame, while such low-frequency events are not detectable at higher redshifts due to the limited bandwidth of CHIME.

Speaker: Tetsuya Hashimoto (National Chung Hsing University)

Hashimoto_ASROC_FRB_2026.pdf

58 An Energy–Duration Correlation for Fast Radio Bursts from the Second CHIME/FRB Catalog.

Fast radio bursts (FRBs) are bright millisecond-duration radio transients from distant galaxies, whose physical origin remains uncertain. Studying relations between burst properties, such as energy and intrinsic duration, may enable the use of FRBs as cosmological probes by providing luminosity distance estimates when combined with spectroscopic redshifts, without relying on the $H_0$--$f_{\rm IGM}$ degeneracy inherent in dispersion measure-based methods. Previous studies reported a possible energy--duration correlation in non-repeating FRBs ($p \approx 10^{-3}$); however, earlier analyses were based on relatively small samples, leading to large statistical uncertainties in the measured relation. In this work, we update the intrinsic energy--duration relation using the recently released CHIME/FRB Second Catalog. After applying selection criteria, we analyze 2304 non-repeating FRBs, providing the largest sample used to study this relation to date. For each burst, we compute the rest-frame intrinsic duration and isotropic burst energy integrated over a 400~MHz bandwidth and investigate their correlation across multiple redshift intervals ($0 < z < 0.3$, $0.3 < z < 0.5$, $0.5 < z < 1.0$, and $1.0 < z < 1.5$). We find a positive correlation between burst energy and intrinsic duration in all redshift bins, with best-fit slopes of $b \sim 0.13$--$0.21$. The positive slopes indicate that more energetic bursts tend to have longer intrinsic durations. The corresponding $p$-values are $2.9 \times 10^{-5}$, $3.9 \times 10^{-6}$, $2.5 \times 10^{-5}$, and $1.6 \times 10^{-2}$, indicating strong statistical significance.The persistence of the $E$--$w$ relation across all redshift bins suggests an intrinsic origin; however, its strong correlation with $\tau_{\rm scat}$ indicates that propagation effects remain a significant contributor to the observed dispersion. The much larger CHIME/FRB Catalog 2 sample significantly improves the statistical robustness compared to earlier studies based on smaller datasets. These results suggest that the energy--duration relation reflects an intrinsic physical property of non-repeating FRB emission and may provide a potential tool for future FRB-based cosmological studies.

Speaker: Mr Chakrapani Reddy (National Chung Hsing University)

Solar system and exoplanets

Convener: Ing-Guey Jiang (National Tsing Hua University)

59 Binding Energy and desorption pre-exponential factors: two key desorption parameters for astrophysical ice chemistry

The binding energy and desorption pre-exponential factor are key parameters in astrophysical ice chemistry, governing gas-surface processes that ultimately yield the astrophysical observations of a wide variety of gas-phase chemical species in cold environments (e.g., prestellar cores). Without accurate values, contemporary astrochemical models are compelled to rely on wild guesses, often producing misleading results. While the former has been well addressed in recent years by both experimental and computational methods, the latter remains somewhat ill-defined, and different schemes have been proposed in the literature for its evaluation. In the astrochemistry context, binding energies and pre-exponential factors are key parameters that enter microkinetic models for studying the evolution over time of the chemical species in the universe. We focus on these parameters controlling the thermal desorption of ices and how these determine pathways toward molecular complexity and define the location of snowlines, which ultimately influence the planet formation process. We provide binding energies for astrochemically important radicals, alcohols, thiols, and their plausible precursors, as predicted by quantum-chemical computations, with amorphous solid water as the substrate and water as the principal constituent of interstellar ice. Conventional models often rely on single-valued binding energies, overlooking the intrinsic distribution arising from the diversity of adsorption sites. We incorporate a distribution of binding energies to capture the realistic variation in adsorption strengths. Our calculations provide a range of binding energy values rather than just a single estimate. We incorporated our calculated binding energies in astrochemical models, revealing significant effects on predicted molecular abundances.

Speaker: Milan Sil (Institute of Astronomy, National Tsing Hua University)

60 The Influence of Aerosol-Driven Transport on the D/H Stratification in the Middle Atmosphere of Venus

The atmospheric dynamics of Venus's mesosphere (60–120 km) present a long-standing scientific challenge, characterized by complex interactions between meridional circulation and photochemistry. A recent, unexpected observation revealed a massive increase in the gas-phase deuterium-to-hydrogen (D/H) ratio in this layer, rising from 162 to 1,519 times Earth’s standard between 70 and 108 km in altitude, suggesting the existence of a powerful transport mechanism, possibly an aerosol-driven cycle and a meridional circulation (Mahieux et al., 2024).

To quantitatively test this hypothesis, this study employs the 2D KINETIC (Yung et al., 2009) and 1D VULCAN (Tsai et al., 2017; Dai et al., 2024) Chemical Transport Models (CTMs). Both models were updated to integrate the requisite physics, including a temperature-dependent frozen-reservoir switch, bimodal aerosol transport, altitude-dependent condensation fractionation, and differential photolysis.

Our simulations demonstrate that the theoretical pathways for upward transport and high-altitude release are numerically viable and capable of producing upper-atmosphere D/H anomalies. Both models correctly sequester deuterium into the condensed phase near the cold trap (80–95 km). However, when strictly enforcing physically realistic, mass-conserving co-transport of both H₂O and HDO, the extreme upper-mesospheric D/H enrichment collapses to a low-amplitude ceiling in our models. These results indicate that the fundamental bottleneck is not the atmospheric transport architecture itself, but rather the insufficient isotopic enrichment within the aerosol reservoir prior to its ascent. Ultimately, this structural limitation suggests that replicating the observed stratification requires either a stronger or repeated Rayleigh-like fractionation. This study provides critical new constraints for understanding Venus's atmospheric evolution and historical water loss (Donahue et al., 1982).

This presentation is dedicated to the memory of Professor Yuk L. Yung (1946-2026).

Speaker: Cheng-An Hsieh (National Taiwan University)

61 A Photodynamical Pipeline for Exomoon Detection Using Transit Timing Variations

The detection of exomoons, natural satellites orbiting exoplanets, remains one of the most challenging and intriguing problems in modern astronomy. In this work, we develop a photodynamical pipeline to search for exomoon signatures using transit timing variations (TTV). By analyzing periodic shifts in transit mid-times, we aim to identify the dynamical effects induced by a potential orbiting moon.

We apply this approach to the HAT-P-1 b system using 16 high-quality transits from multiple TESS sectors. The observed light curves are used to construct a physically consistent star-planet-moon model, and synthetic transit signals are generated under realistic observational conditions. Particular attention is given to improving timing precision through optimized sampling and noise treatment. The resulting TTV signals are compared with theoretical models, allowing us to explore whether an exomoon-like configuration can reproduce the observed variations. This study demonstrates how combining high-precision photometry with dynamical modeling can provide indirect but powerful constraints on exomoon candidates, contributing to our understanding of the diversity and formation of planetary systems beyond our Solar System.

Speaker: Prangsutip Cherdwongsung (National Tsing Hua University)

62 Solar Radio Burst (SRB) Classification and Catalog during the Solar Cycle 25: Late-Maximum Phase

A comprehensive catalog of Solar Radio bursts that is recorded from a Dual Dipole Antenna operating in Philippines at RTU Baras, specifically located the coordinates of 14°34′34.4″N, 121°15′53.3″E with a moderate elevation on the fringes of the Sierra Madre Mountain range. The antenna detects solar radio bursts between 16 MHz and 24 MHz using a calibrated software-defined radio (SDR) receiver during the interval 1:00:00 UTC to 7:00:00 UTC which is operated daily. With the objective of enhancing local observational solar radio emissions through continuous monitoring of dynamic spectrogram analysis and manual verification and classification (Solar Radio bursts types I - IV), and the measurement of key parameters such as duration of the radio bursts, frequency span, drift rate, peak flux above noise floor considering the RFI environment and the ionospheric cutoff frequency. Through cataloguing the total observations of more than 50 solar radio bursts observed in the locality of Baras . The results characterized the burst type occurrences rate, the morphological and the spectral drift properties of the solar radio bursts in the high frequency range (16 Mhz to 24 Mhz), during late maximum phase of the solar cycle 25. The catalog provides a comprehensive analysis that contributes to the ground-based solar and space weather monitoring in the Philippines.

Speaker: Roberto III Serrano (Rizal Technological University)

63 Modeling Atmospheric Chemistry of the Ultra Low Density Exoplanet WASP-193b

The recently discovered exoplanet WASP-193 b represents an extreme example of a “cotton candy” gas giant exoplanet, exhibiting an exceptionally low density (⍴=0.059±0.014 g·cm^-3) that current planetary evolution models cannot explain. With a Jupiter-like radius (R_p=1.464 R_{Jup}) but a mass of only 0.139 M_{Jup}, this highly irradiated planet (T_eq=1254 K) challenges our understanding of atmospheric inflation and mass-loss mechanisms (Barkaoui et al., 2024). This population of extremely low-density planets have inflated radii that require additional heating mechanisms, such as tidal or ohmic dissipation. To investigate the physical processes driving WASP-193 b’s anomalous structure, we employ VULCAN, a comprehensive photochemical kinetics model, to simulate its thermochemical equilibrium and disequilibrium chemistry under intense stellar irradiation. The model predicts atmospheric composition and vertical thermal structure. We will apply climate and photochemical modelling to explore the observability of internal heating, assessing how internal energy flux influences molecular abundances and spectral features. Our results will constrain the role of internal heating and mass loss in producing inflated atmospheres, providing key theoretical insights into this emerging class of ultra-low-density exoplanets.

Speaker: Cheng-An Hsieh (National Taiwan University)

20260516_ASROC_193b.pdf

64 Evidence for a Non-Transiting Companion in the TOI-2109 System via Transit Timing Variation

Transit Timing Variation (TTV) is a robust method for detecting
non-transiting planets in multi-planetary systems, especially those near
Mean Motion Resonance (MMR). In this study, we focus on TOI-2109 b, one
of the few known exoplanets with an orbital period shorter than 1 day.
To achieve the precision necessary to detect these minute gravitational
perturbations, we integrated high-cadence space-based photometry from
TESS and CHEOPS with long-baseline ground-based observations. Our
dataset comprises nearly 100 transit epochs, providing a comprehensive
baseline for TTV modelling.

With these data, we performed a model comparison across four scenarios:
a constant linear ephemeris, orbital decay, apsidal precession due to
gravitational interactions and general relativistic effects, and
sinusoidal models to identify periodic oscillations. To account for
potential multi-planetary interactions, we also employed a two-planet
dynamical model obtained from N-body simulations. While such planets are
highly susceptible to orbital decay via tidal dissipation, our analysis
reveals evidence of a potential additional planet within the system. Our
results suggest the presence of an additional planetary companion near a
MMR. This study highlights the importance of combining multiple
modelling approaches and long-term dynamical simulations to uncover
hidden planetary companions and a better understanding of the complex
gravitational interactions in ultra-short-period exoplanetary systems.

Speaker: Kaviya Parthasarathy (National Tsing Hua University)

65 Exploring Possible Additional Planets near the Hot Jupiter WASP-18 b through Transit Timing Variations

Transit light-curve observations play important roles in the study of
exoplanetary systems as they enable the determination of physical and
orbital parameters of exoplanets through transit timing variations
(TTVs).
The TTV method is particularly powerful for detecting additional
low-mass planets within a system. In this work, we analyze 176 light
curves, including 132 from TESS and 12 from CHEOPS. The long baseline
TTV provides constraints on the existence of additional planets. This
gives us an opportunity to investigate possible new planets around the
hot Jupiter WASP-18 b.

Speaker: Hsin-Min Liu (NTHU)

Banquet

Sun, May 17

Plenary talk: Origin of the first Solar System solids in out-of-equilibrium condensation processes

Convener: Yueh-Ning Lee (National Taiwan Normal University)

66 Origin of the first Solar System solids in out-of-equilibrium condensation processes

The formation of the first solids in protoplanetary disks sets the chemical foundations of planetary systems, yet their origin remains poorly understood. Classical models assume equilibrium condensation in a cooling gas, but increasing observational and cosmochemical evidence suggests that this assumption is not valid in dynamically evolving disks. Infrared observations (Spitzer, JWST) reveal strong spatial and temporal variability in dust mineralogy, while meteorites record discrete redox states and mineral assemblages that are difficult to reconcile with equilibrium chemistry alone.
Here, I present my recent work with an innovative method, in which I compute time-dependent gas–solid reactions along realistic pressure–temperature–time (P–T–t) trajectories. Our results show that mineralogy and oxidation state are primarily controlled by cooling rate and pressure, rather than by bulk composition. Remarkably, this approach naturally reproduces the three main classes of chondritic materials (enstatite, ordinary, and carbonaceous) and their redox diversity, without invoking large-scale chemical gradients.

A key implication is that protoplanetary disks behave as time-dependent thermochemical reactors. In this context, processes such as accretion bursts, vertical transport, and disk winds drive rapid heating and cooling cycles, leading to kinetically controlled condensation pathways. This framework also predicts the formation of Fe-rich and hydrated minerals directly during condensation, opening new perspectives on the origin of water in terrestrial planets and challenging the classical concept of the snowline.

These results suggest a paradigm shift in which planetary materials record their thermodynamic history rather than their formation location. This work provides a unified framework to connect disk observations, meteoritic records, and exoplanet compositions, and opens new directions for understanding the chemical diversity of planetary systems.

Speaker: Prof. Sebastien Charnoz (Université de Paris Cité)

General assembly and award presentation

Convener: Albert Kong

Coffee break

Early Career Scientists

Convener: Daniel Harsono

67 Short-term Dynamics of Short-Period Comets

We summarized our simulation results of the short-term dynamical evolution on 500 numbered Short-Period Comets over a 2000-year window (between 1000 and 3000 A.D.). To understand their evolution history, we classified the comets we studied into several groups based on the dynamical features: the recent semi-major/perihelion (a/q) jump, the Tisserand parameter reversion, and the temporary satellite captured by Jupiter.

We confidently identify 6214 planet-encounter events on 458 comets in 555k cometo-years, with impact distances smaller than 3 Hill radii of the planet. Statistical results for encounter distance and the change in each orbital element will be given. The Tisserand parameter indicates which planet a minor object is gravitationally bound to. We found two types of Tisserand reversion—fast and slow—marking orbital transfers between the Jupiter and Saturn domains. The fast Tisserand reversion occurs at the planet's encounter and results in a sudden, significant orbital change, whereas the slow reversions do not. We find that objects undergoing "fast" reversion frequently overlap with those experiencing recent a/q jumps, suggesting they are "fresh" Jupiter-Family Comets (JFCs) recently migrated into the inner solar system. Notably, three new Temporarily Satellite Captured (TSC) comets are identified (345P, 441P, 467P) in this study.

Crucially, we find a potential correlation between these dynamical histories and cometary chemistry. None of the "low-activity" comets identified in previous surveys (Ye et al. 2016) qualify as fresh JFCs in our model. Furthermore, our identified fresh JFCs consistently fall into the low-carbon/OH groups (A’Hearn et al. 1995). While the sample size is limited, we need more observational evidence for the possible connection and to explain the physical interpretation.

Speaker: Yu-Chi Cheng (IANCU)

68 Probing AU-Scale Magnetic-Field Reversals in the ISM with Pulsar Scintillation

AU-scale magnetic structures in the interstellar medium (ISM) — particularly current sheets formed at magnetic-field reversals — are predicted to strongly influence cosmic-ray transport, yet direct observations at these scales have remained inaccessible. Traditional Faraday rotation measure (RM) techniques lack the sub-parsec resolution required and are contaminated by ionospheric systematics.

We present a new method that exploits interstellar scintillation to resolve AU-scale magnetic geometry. By applying phase retrieval to isolate birefringence-induced polarization between proximal scattered ray paths, we perform differential RM measurements that isolate the magnetic signal of AU-scale foreground structures — circumventing ionospheric contamination by over two orders of magnitude in RM precision.

Applying this method to archival VLBI observations of PSR B0834+06, we identify two ray paths grazing opposite sides of a foreground current sheet with AU-scale transverse thickness. We measure a branch-to-branch RM offset of $(−9.4±3.3)×10^{−3} \text{ rad m}^{-2}$ (2.8$\sigma$), implying a magnetic-field reversal of $|\Delta\langle B_\parallel\rangle|\simeq 4.4±2.1 \,\mu \text G$. This result provides the first suggestive observational evidence for AU-scale magnetic-field reversal in the diffuse ISM, with direct implications for cosmic-ray transport and pulsar timing array experiments.

Speaker: Jacob Yen (ASIAA)

69 Testing the formation of an aspherical circumstellar medium around supernova progenitors via rotation-driven mass loss

The presence of dense circumstellar medium (CSM) around core-collapse supernova (SN) progenitors has been universally realized lately through the radiative properties of SN-CSM interaction immediately after the explosion, although the physical origin of the CSM formation has not yet been established. Recent detections of significant polarization in early-phase Type IIP SNe 2023ixf and 2024ggi have advocated the possibility of the aspherical distribution of the dense CSM, which could be a promising clue to understanding the mass-loss mechanism happening in the final phase of massive stars. Here, we note that simply raising the disk-like CSM originating from binary interaction can cause self-inconsistency between the progenitor-CSM setup and observational facts. Instead, we examine the alternative scenario of whether stellar rotation can affect the resultant CSM formation by considering trajectory alteration, stellar surface flattening, centrifugal force, and gravity darkening. We find that these stellar rotation effects will prominently emerge only when the stellar rotation speed is faster than $\sim20\%$ of the critical rotation. This rotation rate is even faster than possibly inferred for Betelgeuse. Explaning the polarization degree in SN 2023ixf and 2024ggi requires similarly fast stellar rotation for a single red supergiant. This indicates the plausibility of other scenarios for the aphserical CSM formation, including the spinning up of the progenitor star via stellar merger and intrinsically aspherical mass-loss activity.

Speaker: Dr Tomoki Matsuoka (The University of Tokyo / ASIAA)

70 JWST Edge-on Disk Ice (JEDIce): An analysis of PAH signatures within the disks

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous carbonaceous molecules in the interstellar medium, tracing the interaction between ultraviolet radiation fields and molecular material. In protoplanetary disks, they are widely used as diagnostics of disk surface chemistry, UV processing, and ionization structure. Using recently obtained JWST/NIRSpec and MIRI IFU observations of the edge-on disks ESO-H$\alpha$ 574, HV Tau C, OphE MM3, Oph 163131, Flying Saucer, and LkH$\alpha$ 263C, we analyze near- and mid-infrared emission features commonly attributed to PAHs. We first assess the spatial origin of the emission to distinguish disk-associated PAH features from background cloud contamination, exploiting the edge-on geometries and spatially resolved IFU data. For sources where the emission is demonstrably disk-confined, we derive physically motivated band ratios (i.e., 3.3/11.3 $\mu m$, 11.3/7.7 $\mu m$, and 3.4/3.3 $\mu m$) to constrain PAH representative sizes as well as ionization and aliphatic fractions. Where signal-to-noise permits, we construct spatially resolved ratios to trace vertical and radial variations in PAH properties across the disks. Preliminary results indicate predominantly small- to medium-sized PAHs ($N_c \approx 30–100$), with regionally dependent ionization states that are either strongly neutral or strongly ionized. Several systems exhibit systematic vertical gradients consistent with irradiation-driven processing in disk surface layers, while mid-plane regions show suppressed aromatic emission, likely due to shielding and grain growth. These findings demonstrate that PAH emission in edge-on disks provides a spatially resolved diagnostic of disk irradiation and the chemical state of PAHs, including ionization and molecular structure. When combined with JWST constraints on gas excitation and ice composition, PAHs emerge as a powerful probe of radiation-driven evolution, ionization balance, and the processing of aromatic carbon during planet formation.

Speaker: Charles Mentzer (National Tsing Hua University)

71 Spiral-like gas features and cold fronts driven by AGN feedback in cool-core clusters

Spiral structures and cold fronts in cool-core (CC) galaxy clusters are almost universally attributed to minor merger-induced gas sloshing. However, many CC clusters appear dynamically relaxed with no visible perturber, challenging this interpretation. Using three-dimensional cosmic-ray magnetohydrodynamic simulations of self-regulated AGN feedback in a Perseus-like cluster, we show that precessing, CR-dominated jets naturally produce spiral-like structures extending to ~150 kpc and accompanying cold fronts — driven by coherent fallback of jet-uplifted gas during AGN quiescent phases, without any external perturbation. Comparing kinematic signatures against XRISM/Resolve observations of Perseus, we find that while a merger simulation reproduces large-scale velocity gradients, it systematically underpredicts gas motions in the central ~30 kpc, where AGN-driven motions dominate. We further show that AGN quiescent phases produce a tangential bias in both velocity and magnetic fields, stabilising cold fronts against Kelvin–Helmholtz instabilities.

Speaker: Majidul Rahaman (IoA, NTHU, Taiwan)

Education and public outreach

Convener: Hao-Yuan Duan

72 與AI探索天文 創造專屬的天文探索體驗

作為一個教育娛樂品牌，《與AI探索天文》想激發大眾的想像與創意。我會分享如何運用AI將遙遠的天文知識拆解、重組，連結到生活與不同領域，創造有趣的探索體驗，拉近大眾與星空的距離。

Speaker: Mr Yi-Hao Su (與AI探索天文(AstroEdu.AI))

73 香港可觀自然教育中心暨天文館 30年及望遠鏡更新

可觀自然教育中心暨天文館是香港一所成立30年的天文科普中心，每年接待超過3萬名學生及公眾，中心的0.5米望遠鏡剛剛退役並正更換成0.7米望遠鏡。2024年起，中心參加了香港賽馬會組織的探索科學活動，在全港小學推動探究式科學教育。報告會回顧可觀三十年由建台到今天的珍貴歷史，和介紹望遠鏡更新的經驗。

Speaker: Sze-leung Cheung (Ho Koon Nature Education cum Astronomical Centre)

74 IAU的天文普及、恆星命名工作

本報告會介紹國際天文學聯合會C2天文普及委員會，以及恆星命名委員會的工作。這些恆星名稱涵蓋了多種文化地理和語言，包括古希臘語、阿拉伯語、漢語、達雅克語、荷蘭語、埃及語、英語、法語、希臘羅馬語、希臘語、梵語、拉丁語、馬來語、馬紹爾語、薩米語和蘇美爾語、科伊桑語。天文學和夜空在全球文化中都具有深遠的意義，而這種多樣性也凸顯了這一點。來自中國星名的恆星中有周、軍南門、帛度、屠肆左、衡、奎、 庫樓、豕目等。

Speaker: Mr Sze-leung Cheung (IAU Comission C2 / WG on Star Names)

75 Exploring the Solar System through Hands-on Outreach

When asked simple questions such as “How big is the Earth, the Moon, and the Sun?”, we can easily provide numerical answers: the Earth has a diameter of about 12,000 km, the Moon about 3,400 km, and the Sun about 696,000 km. However, for most of the public, these numbers remain difficult to understand, especially for those without a strong sense of scale.
To promote astronomy education, the Estuary Planetarium team developed a hands-on outreach program based on a model of the Solar System scaled down by a factor of 1:3 billion. In our activities, participants can not only construct the scale size of our Solar system but also learn the characteristics of each plant through painting. In this presentation, we will share our design approach, teaching experience, and practical tools for improving public understanding of astronomy.

Speaker: Hsiang-Yu Chen (National Central University)

Lunch and departure