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Evolution of the Accretion Disk–Corona during the Bright Hard-to-soft State Transition: A Reflection Spectroscopic Study with GX 339–4

Sridhar, Navin and García, Javier A. and Steiner, James F. and Connors, Riley M. T. and Grinberg, Victoria and Harrison, Fiona A. (2020) Evolution of the Accretion Disk–Corona during the Bright Hard-to-soft State Transition: A Reflection Spectroscopic Study with GX 339–4. Astrophysical Journal, 890 (1). Art. No. 53. ISSN 1538-4357.

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We present the analysis of several observations of the black hole binary GX 339–4 during its bright intermediate states from two different outbursts (2002 and 2004), as observed by the RXTE/Proportional Counter Array. We perform a consistent study of its reflection spectrum by employing the RELXILL family of relativistic reflection models to probe the evolutionary properties of the accretion disk including the inner disk radius (R_(in)), ionization parameter (ξ), temperatures of the inner disk (T_(in)), corona (kT_e), and its optical depth (τ). Our analysis indicates that the disk inner edge approaches the innermost stable circular orbit during the early onset of the bright hard state, and that the truncation radius of the disk remains low (<9 R_g) throughout the transition from hard to soft state. This suggests that the changes observed in the accretion disk properties during the state transition are driven by variation in accretion rate, and not necessarily due to changes in the inner disk's radius. We compare the aforementioned disk properties in two different outbursts with state transitions occurring at dissimilar luminosities and find identical evolutionary trends in the disk properties, with differences only seen in the corona's kT_e and τ. We also perform an analysis by employing a self-consistent Comptonized accretion disk model accounting for the scatter of disk photons by the corona, and measure the low inner disk truncation radius across the bright intermediate states, using the temperature-dependent values of the spectral hardening factor, thereby independently confirming our results from the reflection analysis.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Sridhar, Navin0000-0002-5519-9550
García, Javier A.0000-0003-3828-2448
Steiner, James F.0000-0002-5872-6061
Connors, Riley M. T.0000-0002-8908-759X
Grinberg, Victoria0000-0003-2538-0188
Harrison, Fiona A.0000-0003-2992-8024
Additional Information:© 2020 The American Astronomical Society. Received 2019 September 9; revised 2019 December 18; accepted 2019 December 22; published 2020 February 12. N.S. acknowledges the support from DST-INSPIRE, Caltech SURF, and Columbia University Dean's fellowships. J.A.G. acknowledges the support from NASA grant 80NSSC19K1020 and from the Alexander von Humboldt Foundation. R.M.T.C. has been supported by NASA ADAP grant 80NSSC17K0515. V.G. is supported through the Margarete von Wrangell fellowship of the ESF and the Ministry of Science, Research and the Arts Baden-Württemberg. We also thank Ronald A. Remillard for his contribution toward processing the data, which have been used in our analysis. This work was partially supported under NASA contract No. NNG08FD60C. Facility: RXTE (PCA). Software: xspec v12.9.1q (Arnaud 1996), relxill v1.4 (Dauser et al. 2014; García et al. 2014a), xillver (García & Kallman 2010; García et al. 2013), pcacorr (García et al. 2014b).
Group:Astronomy Department, Space Radiation Laboratory
Funding AgencyGrant Number
Department of Science and Technology (India)UNSPECIFIED
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Columbia UniversityUNSPECIFIED
Alexander von Humboldt FoundationUNSPECIFIED
Baden-Württemberg StiftungUNSPECIFIED
Subject Keywords:High energy astrophysics; Compact objects; Black hole physics; Low-mass x-ray binary stars; Accretion; X-ray astronomy; Spectroscopy; Astronomy data modeling; X-ray sources; General relativity; Gravitation; Astrophysical black holes
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: High energy astrophysics (739); Compact objects (288); Black hole physics (159); Low-mass x-ray binary stars (939); Accretion (14); X-ray astronomy (1810); Spectroscopy (1558); Astronomy data modeling (1859)
Record Number:CaltechAUTHORS:20200212-134110015
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Official Citation:Navin Sridhar et al 2020 ApJ 890 53
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101247
Deposited By: Tony Diaz
Deposited On:12 Feb 2020 22:04
Last Modified:10 Dec 2020 21:41

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