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Description
The authors describe the global X-ray properties of the point source population in the grand-design spiral galaxy M 101, as seen with XMM-Newton. 108 X-ray sources are detected within the D<sub>25</sub> ellipse (~28.8 arcminutes diameter) of M101, of which ~24 are estimated to be background galaxies. Multiwavelength cross-correlations show that 20 sources are coincident with H II regions and/or supernova remnants (SNRs), seven have identified/candidate background galaxy counterparts, six are coincident with foreground stars and one has a radio counterpart. While the spectral and timing properties of the brightest sources were presented by Jenkins et al. (2004, MNRAS, 349, 404: Paper I), in the present analysis the authors apply an X-ray colour classification scheme to split the entire source population into different types, i.e. X-ray binaries (XRBs), SNRs, absorbed sources, background sources and supersoft sources (SSSs). Approximately 60% of the population can be classified as XRBs, although there is source contamination from background active galactic nuclei (AGN) in this category as they have similar spectral shapes in the X-ray regime. 15 sources have X-ray colours consistent with SNRs, three of which correlate with known SNR/HII radio sources. Another two are promising new candidates for SNRs, one is unidentified, and the remainder are a mixture of foreground stars, bright soft XRBs and AGN candidates. The authors also detect 14 candidate SSSs, with significant detections in the softest X-ray band (0.3 - 1 keV) only. 16 sources display short-term variability during the XMM-Newton observation, twelve of which fall into the XRB category, giving additional evidence of their accreting nature. Using archival Chandra and ROSAT High Resolution Imager data, the authors find that ~40% of the XMM sources show long-term variability over a baseline of up to ~10 yr, and eight sources display potential transient behaviour between observations. Sources with significant flux variations between the XMM and Chandra observations show a mixture of softening and hardening with increasing luminosity. The spectral and timing properties of the sources coincident with M 101 confirm that its X-ray source population is dominated by accreting XRBs. The authors cross-correlated the XMM-Newton source list with previous X-ray observations of M 101. For the Chandra observations detailed in Section 2 of the reference paper, they matched on-axis sources (whose positions are generally accurate to ~1 arcsec) to within the XMM-Newton 3-sigma errors. For off-axis sources, the decreasing Chandra positional accuracy to ~2 arcsec was also taken into account. However, given the large PSF of XMM-Newton (~6 arcsec FWHM), they also checked for any contamination from additional fainter sources detected only by Chandra by searching for sources that lie within 15 arcsec of the XMM-Newton source positions (this corresponds to the on-axis 68% energy cut-out radius used in emldetect). In total, 71 XMM-Newton sources were unambiguously matched to single Chandra sources within the 3-sigma errors, whereas the nuclear source is resolved into two sources by Chandra. These matches are listed in this table, as are additional sources matching to within 15 arcsec. For completeness, both the CXOU designations of Kilgard et al. (2005, ApJS, 159, 214) and equivalent source source numbers from Pence et al. (2001, ApJ, 561, 189) are given. M 101 was observed with XMM-Newton for 42.8 ks on 2002 June 4 (Obs ID 0104260101). The EPIC MOS-1, MOS-2 and PN cameras were operated with medium filters in the 'Prime Full Window' mode, which utilizes the full ~ 30-arcmin field of view of XMM-Newton, covering the entire D<sub>25</sub> ellipse of M101. This table was created by the HEASARC in October 2011 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/357/401">CDS Catalog J/MNRAS/357/401</a> files table1.dat and table2.dat. This is a service provided by NASA HEASARC .
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