Highly Turbulent Outbursts of V404 Cygni, Swift J1858.6-081 and V4641 Sgr : Magnetic Origin?
Abstract
The Galactic transient black hole candidates (BHCs) V404 Cygni, Swift J1858.6-081, and V4641 Sgr belongs to a special category of low-mass X-ray binaries as these sources showed several high intense radio and X-ray flares during their outbursts. Rapid variation in spectral and timing properties are also observed during their outbursts. First, we studied a detailed spectral and timing properties of the 2015 outburst of V404 Cygni. It occurred after ~ 26 years of quiescence. To understand the accretion flow dynamics of these sources and the physical reason behind the flaring activities, we studied these sources under TCAF paradigm. Combined spectra of Swift XRT and BAT data in the energy range of 0.5-150 keV are fitted with the TCAF model fits file. This allowed us to extract physical flow parameters (Keplerian disk and sub-Keplerian halo rates; location and strength of shock) directly from spectral fits. We also estimated equipartition magnetic field strength B, and for V404 Cygni the highest B is obtained at ∼ 900 Gauss. Generally, higher B values are observed before the flares. Other two sources are also studied with the TCAF model, and a comparative result of these sources will be presented.
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E1562C