2018ApJ...867...86P -
Astrophys. J., 867, 86-86 (2018/November-2)
AstroSat and Chandra view of the high soft state of 4U 1630-47 (4U 1630-472): evidence of the disk wind and a rapidly spinning black hole.
PAHARI M., BHATTACHARYYA S., RAO A.R., BHATTACHARYA D., VADAWALE S.V., DEWANGAN G.C., McHARDY I.M., GANDHI P., CORBEL S., SCHULZ N.S. and ALTAMIRANO D.
Abstract (from CDS):
We present the X-ray spectral and timing analysis of the transient black hole X-ray binary 4U 1630-47, observed with the AstroSat, Chandra, and MAXI space missions during its soft X-ray outburst in 2016. The outburst, from the rising phase until the peak, is detected neither in hard X-rays (15-50 keV) by the Swift/BAT nor in radio. Such nondetection, along with the source behavior in the hardness-intensity and color-color diagrams obtained using MAXI data, confirms that both Chandra and AstroSat observations were performed during the HS spectral state. The High Energy Grating (HEG) spectrum from the Chandra High-Energy Transmission Grating Spectrometer shows two strong, moderately blueshifted absorption lines at 6.705–0.002+0.002 keV and 6.974–0.003+0.004 keV, which are produced by Fe XXV and Fe XXVI in a low-velocity ionized disk wind. The corresponding outflow velocity is determined to be 366 ± 56 km s–1. Separate spectral fits of Chandra/HEG, AstroSat/SXT+LAXPC, and Chandra/HEG+AstroSat/SXT+LAXPC data show that the broadband continuum can be well described with a relativistic disk blackbody model, with a disk flux fraction of ∼0.97. Based on the best-fit continuum spectral modeling of Chandra, AstroSat, and Chandra+AstroSat joint spectra and using the Markov chain Monte Carlo simulations, we constrain the spectral hardening factor at 1.56–0.06+0.14 and the dimensionless black hole spin parameter at 0.92 ± 0.04 within the 99.7% confidence interval. Our conclusion of a rapidly spinning black hole in 4U 1630-47 using the continuum spectrum method is in agreement with a previous finding applying the reflection spectral fitting method.
Abstract Copyright:
© 2018. The American Astronomical Society. All rights reserved.
Journal keyword(s):
accretion, accretion disks - methods: data analysis - stars: black holes - X-rays: binaries - X-rays: individual: 4U 1630
Simbad objects:
5
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