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AstroSat observation of GX 5-1: Spectral and timing evolution
- Publication Year :
- 2019
- Publisher :
- arXiv, 2019.
-
Abstract
- We report on the first analysis of an AstroSat observation of the Z-source GX 5–1 on 2017 February 26−27. The hardness-intensity plot reveals that the source traced out the horizontal and normal branches. The 0.8−20 keV spectra from simultaneous SXT and LAXPC data at different locations of the hardness-intensity plot can be described well by disk emission and a thermal Comptonized component. The ratio of the disk flux to the total flux, i.e., the disk flux ratio, increases monotonically along the horizontal branch to the normal one. Thus, the difference between the normal and horizontal branches is that in the normal branch, the disk dominates the flux while in the horizontal one it is the Comptonized component which dominates. The disk flux scales with the inner disk temperature as T in 5.5 and not as T in 4 , suggesting that either the inner radius changes dramatically or that the disk is irradiated by the thermal component changing its hardness factor. The power spectra reveal a quasi-periodic oscillation (QPO) whose frequency changes from ∼30 Hz to 50 Hz. The frequency is found to correlate well with the disk flux ratio. In the 3−20 keV LAXPC band, the r.m.s. of the QPO increases with energy (r.m.s. ∝ E 0.8 ), while the harder X-rays seem to lag the soft ones with a time-delay of milliseconds. The results suggest that the spectral properties of the source are characterized by the disk flux ratio and that the QPO has its origin in the corona producing the thermal Comptonized component.
- Subjects :
- Physics
High Energy Astrophysical Phenomena (astro-ph.HE)
Quasi-periodic oscillation
010308 nuclear & particles physics
Astrophysics::High Energy Astrophysical Phenomena
Spectral properties
Flux
FOS: Physical sciences
Astronomy and Astrophysics
Astrophysics
01 natural sciences
Spectral line
Flux ratio
Space and Planetary Science
0103 physical sciences
Thermal
Irradiation
Astrophysics - High Energy Astrophysical Phenomena
010303 astronomy & astrophysics
Energy (signal processing)
Subjects
Details
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....6991a196ec171951839df1b2bd2b430e
- Full Text :
- https://doi.org/10.48550/arxiv.1903.11986