Swift J004234.8+410417, a new X-ray transient in M 31
ATel #6354; R. Sturm, J. Greiner, W. Pietsch, F. Haberl (MPE, Germany)
on 30 Jul 2014; 12:42 UT
Credential Certification: Richard Sturm (rsturm@mpe.mpg.de)
Subjects: X-ray, Binary, Black Hole, Neutron Star, Transient
We report the discovery of an X-ray transient (Swift J004234.8+410417)
in a monitoring observation of the central region of the Andromeda Galaxy (M 31)
with the XRT on board the Swift satellite (ObsID 00032702064) on 2014-07-29 from 19:09 to 22:45 (UT).
The source is detected at RA=00:42:34.8 Dec=+41:04:18 (J2000, total uncertainty 5.8")
with 14.9±6.5 net counts in 2242 s net exposure.
No X-ray source is listed at this position in previous M 31 X-ray catalogues.
By fitting an absorbed power-law model with C statistic and NH set to 6 ×1020cm-2, we estimate a photon index of Γ=2.2 (1.5-2.8)
and a flux of 1.7 (1.0-2.6) × 10-13erg cm-2 s-1 in the 0.3-5.0 keV band.
For a source in M 31 (780 kpc distance), this corresponds to an unabsorbed luminosity of 1.6 × 1037erg s-1.
Comparing two exposures starting at 19:09 and 22:23 indicates an increase of the flux by a factor of ~2 within the observation.
The X-ray spectrum and flux evolution suggest an X-ray binary in M 31.
All uncertainties are given for 90% confidence.
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.
