Insights into the phase-dependent cyclotron line feature in XTE J1946+274: an AstroSat and Insight-HXMT view

被引:3
作者
Devaraj, Ashwin [1 ,2 ]
Sharma, Rahul [1 ]
Nagesh, Shwetha [1 ,3 ]
Paul, Biswajit [1 ]
机构
[1] Raman Res Inst, Sadashivanagar 560080, Bangalore, India
[2] Indian Inst Sci, Joint Astron Programme, Bangalore 560012, India
[3] Texas Tech Univ, Dept Phys & Astron, Box 41051, Lubbock, TX 79409 USA
关键词
stars: neutron; pulsars: general; X-rays: binaries; X-rays: individual: XTE J1946+274; X-RAY PULSAR; NEUTRON-STAR; LUMINOSITY DEPENDENCE; BACKGROUND MODEL; GX; 304-1; ENERGY; ACCRETION; DISCOVERY; EVOLUTION; OUTBURST;
D O I
10.1093/mnras/stad3886
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
XTE J1946+274 is a Be/X-ray binary with a 15.8 s spin period and 172 d orbital period. Using RXTE/PCA data of the 1998 outburst, a cyclotron line around 37 keV was reported. The presence of this line, its dependence on the pulse phase, and its variation with luminosity have been of some debate since. In this work, we present the re-analysis of two AstroSat observations: one made during the rising phase of the 2018 outburst and the other during the declining phase of the 2021 outburst. We also present a new analysis of the Insight-HXMT observations of the source at the peak of the 2018 outburst. We find the source to be spinning up over the course of the outburst and spinning down between the two outbursts. We report the presence of a higher cyclotron line energy using the 2018 AstroSat observation (similar to 45 keV) and 2018 Insight-HXMT observation (similar to 50 keV) and a line at similar to 40 keV during the declining phase of the 2021 outburst using data from AstroSat. We also investigate the pulse phase dependence of the cyclotron line parameters and find that the line is significantly detected in all the phases of both AstroSat observations, along with showing variation with the pulse phase. This differs from the previous results reported using BeppoSAX and NuSTAR. We explain this behaviour of the cyclotron line to be due to photon spawning and different accretion column radii at the two poles of this neutron star.
引用
收藏
页码:11015 / 11025
页数:11
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