INVESTIGATING SLIM DISK SOLUTIONS FOR HLX-1 IN ESO 243-49
- Institut de Recherche en Astrophysique and Planetologie (IRAP), Universite de Toulouse, UPS, 9 Avenue du colonel Roche, 31028 Toulouse Cedex 4 (France)
- Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan)
- Institut d'Astrophysique de Paris, UMR 7095 CNRS, UPMC Universite Paris 06, 98bis Boulevard Arago, 75014 Paris (France)
- Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-67, Cambridge, MA 02138 (United States)
- NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
The hyperluminous X-ray source HLX-1 in the galaxy ESO 243-49, currently the best intermediate-mass black hole (BH) candidate, displays spectral transitions similar to those observed in Galactic BH binaries, but with a luminosity 100-1000 times higher. We investigated the X-ray properties of this unique source by fitting multi-epoch data collected by Swift, XMM-Newton, and Chandra with a disk model computing spectra for a wide range of sub- and super-Eddington accretion rates assuming a non-spinning BH and a face-on disk (i = 0 Degree-Sign ). Under these assumptions we find that the BH in HLX-1 is in the intermediate-mass range ({approx}2 Multiplication-Sign 10{sup 4} M{sub Sun }) and the accretion flow is in the sub-Eddington regime. The disk radiation efficiency is {eta} = 0.11 {+-} 0.03. We also show that the source does follow the L{sub X} {proportional_to} T{sup 4} relation for our mass estimate. At the outburst peaks, the source radiates near the Eddington limit. The accretion rate then stays constant around 4 Multiplication-Sign 10{sup -4} M{sub Sun} yr{sup -1} for several days and then decreases exponentially. Such 'plateaus' in the accretion rate could be evidence that enhanced mass-transfer rate is the driving outburst mechanism in HLX-1. We also report on the new outburst observed in 2011 August by the Swift X-Ray Telescope. The time of this new outburst further strengthens the {approx}1 year recurrence timescale.
- OSTI ID:
- 22037099
- Journal Information:
- Astrophysical Journal, Vol. 752, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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