2025 天文年會 (ASROC Annual Meeting)

Correlation Between Orbital Modulation Parameters and X-ray Flux in Low-Mass X-ray Binary 4U 1820-30

Not scheduled

20m

International Conference Hall 圓形國際會議廳 (College of Management, National Formosa University 國立虎尾科技大學第三校區文理暨管理大樓)

Board: 55

Poster Poster-HE

Speaker

Jun-Lei Wu (Institute of Astronomy, National Central University)

Description

The ultra-compact low mass X-ray binary 4U 1820-30 exhibits a ~3% orbital modulation in its X-ray light curve with a period of 685 seconds, along with a superorbital modulation where the flux varies by a factor of 2 over a period of ~170 days. Zdziarski et al.(2007), using early RXTE data, discovered a correlation between the amplitude of the orbital modulation and the accretion rate, suggesting that the superorbital modulation results from variations in mass transfer from the companion star. To further verify this dependence, we analyzed data collected by RXTE’s PCA and ASM instruments, as well as recent observations from NICER and MAXI. We found a similar dependence not only in the RXTE data but also in the recent NICER and MAXI observations. We therefore confirm that the superorbital modulation of 4U 1820-30 is driven by mass transfer from the companion star.