2005/03/21 by A. K. H. Kong, M. P. Rupen, Kong, A. K. H. +5
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0503465
6 pages, 4 figures; paper presented at the XXII Texas Symposium on Relativistic Astrophysics, Stanford University, Dec. 13-17, 2004
openalex publication_date 2005/03/21 · arxiv created 2005/03/22 · arxiv updated 2009/12/01 · openalex created_date 2022/10/01 · openalex updated_date 2026/07/28
We report the results of Chandra and XMM-Newton observations of an\nultra-luminous supersoft X-ray source in M101. M101 ULX-1 underwent 2 outbursts\nin 2004 during which the peak bolometric luminosities reached 1e41 erg/s. The\noutburst spectra were very soft and can generally be fitted with a blackbody\nmodel with temperatures of 50-160 eV. In two of the observations, absorption\nedges at 0.33 keV, 0.56 keV, 0.66 keV, and 0.88 keV were found. A cool\naccretion disk was also found in the 2004 December outburst. During the low\nluminosity state, a power-law tail was seen up to 7 keV. It is clear the source\nchanged from a low/hard state to a high/soft state. In addition, it showed at\nleast 5 outbursts between 1996 and 2004. This is the first ultra-luminous X-ray\nsource for which recurrent outbursts with state transitions similar to Galactic\nX-ray binaries have been observed. From the Hubble Space Telescope data, we\nfound an optical counterpart to the source. During the 2004 outbursts, we also\nperformed radio and ground-based optical observations. All the results strongly\nsuggest that the accreting object is a > 2800 solar mass black hole.\n