Supersoft X-ray sources in M31: II. ROSAT-detected supersoft sources in the ROSAT, Chandra and XMM eras

Abstract

We have performed Chandra observations during the past 3 years of 5 of the M31 supersoft X-ray sources (SSS) discovered with ROSAT. Surprisingly, only one of these sources has been detected, despite a predicted detection of about 20-80 counts. This has motivated a thorough check of the ROSAT M31 survey I data, including a relaxation of the hardness ratio requirement used to select SSS. This increases the number of SSS identified in survey I by 7. We then carried out a comparison with the ROSAT M31 survey II dataset which had hitherto not been explicitly investigated for SSS. We find that most of the ROSAT survey I sources are not detected, and only two new SSS are identified. The low detection rate in the ROSAT survey II and our Chandra observations implies that the variability time scale of SSS is a few months. If the majority of these sources are close-binary SSS with shell hydrogen burning, it further implies that half of these sources predominantly experience large mass transfer rates.

arXiv commentaccepted for publ. in ApJ; 2 ps-figures; high-quality figures available at http://www.mpe.mpg.de/~jcg/publis.html

References in corpus (13)

• Catalog of supersoft X-ray sources
• X-ray emission from classical and recurrent-novae observed with ROSAT
• The second ROSAT PSPC survey of M31 and the complete ROSAT PSPC source list
• The central region of M31 observed with XMM-Newton. II. Variability of the individual sources
• The central region of M31 observed with XMM-Newton (I. Group properties and diffuse emission)
• Supersoft X-ray Sources in M31: I. A Chandra Survey and an Extension to Quasisoft Sources
• A Synoptic X-ray Study of M31 with the Chandra-HRC
• X-Ray Off States and Optical Variability in CAL 83
• On the X-ray source luminosity distributions in the bulge and disk of M31: First results from XMM-Newton survey
• XMM-Newton observations of Nova LMC 2000
• The discovery of 2.78 hour periodic modulation of the X-ray flux from globular cluster source Bo 158 in M31
• First optical identification of a suprsoft X-ray source in M31
• Supersoft X-Ray Sources in M31

Cited by in corpus (16)

• X-ray source populations in galaxies
• Optical novae: the major class of supersoft X-ray sources in M 31
• BK Lyncis: The Oldest Old Nova?... And a Bellwether for Cataclysmic-Variable Evolution
• XMM-Newton survey of M 31
• Supersoft X-ray Sources in M31: I. A Chandra Survey and an Extension to Quasisoft Sources
• Revisiting the ultraluminous supersoft source in M101: an optically thick outflow model
• On a century of extragalactic novae and the rise of the rapid recurrent novae
• A Close Look at the Population of Supersoft and Quasi-Soft X-Ray Sources Observed in M31 with XMM-Newton
• Time variability of X-ray sources in the M 31 centre field
• X-ray emission from optical novae in M 31
• XMM-Newton discovery of 217 s pulsations in the brightest persistent supersoft X-ray source in M31
• Long-term X-ray Variability Study of IC342 from XMM-Newton Observations
• A new luminous supersoft X-ray source in NGC 300
• Supersoft sources in M 31: Comparing the XMM-Newton Deep Survey, ROSAT and Chandra catalogues
• The supersoft X-ray source in V5116 Sgr I. The high resolution spectra
• SSS in young stellar populations and the "prompt" component of Type Ia supernovae