Weighing the black holes in ultraluminous X-ray sources through timing |
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| Authors: | P. Casella G. Ponti A. Patruno T. Belloni G. Miniutti L. Zampieri |
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| Affiliation: | Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, the Netherlands;APC UniversitéParis 7 Denis Diderot, 75205 Paris Cedex 13, France;Dipartimento di Astronomia, Universitàdegli Studi di Bologna, via Zamboni, 40127 Bologna, Italy;INAF-IASF Bologna, via Gobetti 101, 40129 Bologna, Italy;INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (LC), Italy;Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA;INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy |
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| Abstract: | We describe a new method to estimate the mass of black holes in Ultraluminous X-ray Sources (ULXs). The method is based on the recently discovered 'variability plane', populated by Galactic stellar-mass black-hole candidates (BHCs) and supermassive active galactic nuclei (AGNs), in the parameter space defined by the black-hole mass, accretion rate and characteristic frequency. We apply this method to the two ULXs from which low-frequency quasi-periodic oscillations have been discovered, M82 X-1 and NGC 5408 X-1. For both sources we obtain a black-hole mass in the range 100–1300 M⊙ , thus providing evidence for these two sources to host an intermediate-mass black hole. |
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| Keywords: | accretion, accretion discs black hole physics X-rays: binaries X-rays: individual: M82 X-1 X-rays: individual: NGC 5408 X-1 |
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