XMM–Newton observations of ultraluminous X–ray sources in nearby galaxies

Free access article

Issue		A&A Volume 392, Number 3, September IV 2002


Page(s)		817 - 825
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20020950

A&A 392, 817-825 (2002)
DOI: 10.1051/0004-6361:20020950

XMM-Newton observations of ultraluminous X-ray sources in nearby galaxies

L. Foschini¹, G. Di Cocco¹, L. C. Ho², L. Bassani¹, M. Cappi¹, M. Dadina¹, F. Gianotti¹, G. Malaguti¹, F. Panessa¹, E. Piconcelli¹, J. B. Stephen¹ and M. Trifoglio¹

¹ Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF-CNR) - Sezione di Bologna (Formerly Istituto TeSRE - CNR.) , via Gobetti 101, 40129, Bologna, Italy
² The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA

(Received 6 May 2002 / Accepted 24 June 2002)

Abstract
An XMM-Newton study of ultraluminous X-ray sources (ULX) has been performed in a sample of 10 nearby Seyfert galaxies. Eighteen ULX have been found with positional uncertainty of about 4''. The large collecting area of XMM-Newton makes the statistics sufficient to perform spectral fitting with simple models in 8 cases. The main results of the present minisurvey strengthen the theory that the ULX could be accreting black holes in hard or soft state. In some cases, the contribution of the ULX to the overall X-ray flux appears to be dominant with respect to that of the active nucleus. In addition, 6 ULX present probable counterparts at other wavelengths (optical/infrared, radio). A multiwavelength observing strategy is required to better assess the nature of these sources.

Key words: galaxies: active -- galaxies: general -- X-rays: binaries -- X-rays: galaxies

Offprint request: L. Foschini, foschini@bo.iasf.cnr.it

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