XMMM31J004256.7+411843 in outburst

ATel #5560; R. Sturm, W. Pietsch, F. Hofmann, J. Greiner (MPE, Germany)
on 8 Nov 2013; 11:18 UT
Credential Certification: Richard Sturm (rsturm@mpe.mpg.de)

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In recent monitoring observations of the M31 centre with the Swift satellite, we find an X-ray transient at RA=00:42:57.0 Dec=+41:18:42 (J2000, ePOS=4.26", 90% confidence) that is likely associated with the X-ray binary candidate XMMM31 J004256.7+411843. This source has been recorded in major M31 X-ray catalogues (e.g. Kong et al. 2002, ApJ 577, 738; Williams et al. 2004, ApJ 609, 735; Stiele et al. 2011, A&A 534, 55; and references therein) and seems to have bright outbursts about every year, lasting up to about three months (Williams et al. 2006, ApJ 643, 356; Hofmann et al. 2013, A&A 555, 65). While in 2012 no bright outburst was found within the Swift monitoring, the current outburst follows the yearly trend. By fitting an absorbed power law with C-statistics, we estimate an N_H<3×10²¹cm^-2 and Γ=1.8 (1.1-2.7), as well as net count rates, fluxes and absorption-corrected luminosities in the 0.3-5.0 keV band as listed below.

  
 ObsID          MJD        Exp    Rate            F                 L                
                           [s]    [cts/s]         [10-13erg/cm2/s]  [1037erg/s] 
00032702031     56583.45   1676   <0.004          <1.4              <1.4 
00032702032     56587.39   3801   0.0076±0.0015   3.3±0.8           3.1 
00032702033     56591.08   1965   0.0104±0.0024   4.3±1.2           4.0 
00032702034     56595.01   2135   0.0075±0.0020   2.9±0.9           2.7 
00032702035     56599.02   2692   0.0062±0.0016   2.5±1.0           2.4 

We would like to thank the Swift Team for making these observations possible, in particular N. Gehrels, the duty scientists, as well as the science planners.