A Luminous Recurrent Supersoft X-ray Source in NGC 300

Abstract

We report the results of XMM-Newton observations for an especially luminous supersoft X-ray source (SSS) with bolometric luminosity of 10^39 erg/s in the spiral galaxy NGC 300. The source was detected as a SSS in 1992 and disappeared in subsequent X-ray observations. The source was active again during recent XMM-Newton observations. It appeared to be very soft (kT~60 eV) and very luminous (~10^38 - 10^39 erg/s). The two XMM-Newton observations also reveal that the source went from a ``high'' state to a ``low'' state in 6 days. We also found a 5.4-hr periodicity during the ``low'' state. We consider white dwarf, black hole, and neutron star models to explain the nature of the source.

5 pages, 3 figures, ApJL accepted

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• The Ultraluminous X-ray Sources near the Center of M82
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• A Close Look at the Population of Supersoft and Quasi-Soft X-Ray Sources Observed in M31 with XMM-Newton
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• A Study of Spectral Variability between flaring and non-flaring state in M74 X-1
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