AstroSat View of the Neutron Star Low-mass X-Ray Binary GX 5-1

We present the spectral and timing study of the bright neutron star low-mass X-ray binary GX 5-1 using AstroSat/Large Area X-ray Proportional Counter (LAXPC) and Soft X-ray Telescope observations conducted in 2018. During the observation, the source traces out the complete horizontal branch (HB) and...

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Bibliographic Details
Published in:The Astrophysical journal 2024-12, Vol.977 (2), p.215
Main Authors: Shyam Prakash, V. P., Agrawal, Vivek K.
Format: Article
Language:English
Subjects:
Accretion disks
Binary stars
Blackbody
Compact objects
Corona
Horizontal branch stars
Low-mass x-ray binary stars
Neutron stars
Neutrons
Optical analysis
Optical thickness
Oscillations
Proportional counters
Soft x rays
Spectral analysis
Spectrum analysis
X ray binaries
X ray stars
X ray telescopes
X-ray astronomy
X-rays
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Summary:We present the spectral and timing study of the bright neutron star low-mass X-ray binary GX 5-1 using AstroSat/Large Area X-ray Proportional Counter (LAXPC) and Soft X-ray Telescope observations conducted in 2018. During the observation, the source traces out the complete horizontal branch (HB) and normal branch (NB) of the Z-track in the hardness–intensity diagram (HID). Understanding the spectral and temporal evolution of the source along the Z-track can probe the accretion process in the vicinity of a neutron star. Spectral analysis was performed in the 0.7–20 keV energy range for different segments in the HID using a multitemperature disk blackbody with an average temperature, kTin ∼ 0.47, and a thermal Comptonization model. It is found that the optical depth of the corona drops from ∼7.07 in HB to ∼2.61 in NB. The timing analysis using the LAXPC instrument indicates the presence of quasiperiodic oscillations in HB and NB of the Z-track. The observed QPO frequencies are similar to the characteristic frequencies of horizontal branch oscillations (HBOs) and normal branch oscillations (NBOs). The HBO frequency increases from ∼12 to 40 Hz toward the hard apex. NBOs are observed at ∼5 Hz. The timing studies conducted in soft and hard bands indicate the association of HBO and NBO origin with the nonthermal component. Further research could explore the implications of this relationship for understanding the dynamics of accretion onto neutron stars.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ad93b0