AstroSat/LAXPC view of GX 17+2: spectral evolution along the Z-track
Abstract
In this paper, we present the first results obtained using ∼50 ks observations of the bright low-mass X-ray binary (LMXB) GX 17+2 with Large Area X-ray Proportional Counter (LAXPC) onboard AstroSat. The source traced out a complete Z-track in the hardness intensity diagram (HID). The spectra at different sections of the Z-diagram are well described by either a combination of a thermal Comptonization component, a power-law and a relativistic iron line or a model consisting of a thermal disk component, a single temperature blackbody, a power-law and a relativistic iron line. Fitting the spectra with both phenomenological models suggests that the power-law component is strong in the horizontal branch (HB), becomes weaker as the source moves down the normal branch (NB) and then again becomes stronger as the sources moves up the flaring branch (FB). However, we find that the strength of the power-law component is model dependent, although the trend in the variation of the power-law strength along the Z-track is similar. A simple model composed by a Comptonized emission and power-law component, convolved with the ionized reflection, also describes the spectra very well.
- Publication:
-
Astrophysics and Space Science
- Pub Date:
- February 2020
- DOI:
- 10.1007/s10509-020-3748-0
- arXiv:
- arXiv:2002.04489
- Bibcode:
- 2020Ap&SS.365...41A
- Keywords:
-
- Accretion;
- Accretion discs;
- X-rays: binaries;
- X-rays: individual;
- GX 17+2;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- doi:10.1007/s10509-020-3748-0