Swift follow-up of the M31 ULX candidate
ATel #5752; R. Sturm, W. Pietsch, J. Greiner, F. Haberl (MPE, Germany)
on 10 Jan 2014; 10:42 UT
Credential Certification: Richard Sturm (rsturm@mpe.mpg.de)
Subjects: Ultra-Violet, X-ray, Black Hole, Transient
Referred to by ATel #: 5771
Swift J004327.6+410452 was found as a ULX candidate in M31 (ATel #5743).
We report on an on-axis Swift follow-up observation (ObsID 00033088001), performed on 2014-01-09 between 16:03 and 18:51 UT.
In a 1960 s Swift/XRT exposure the source was found at RA=00:43:27.57 Dec=+41:04:53.1 (J2000, ePOS=3.6", 90% confidence, 1.5" angular separation from previous position)
with a count rate of 0.362±0.014 s-1.
Spectral parameters for a power-law model are consistent with those reported previously
(NH=(2.6±0.5)×1021cm-2 and Γ=2.5±0.2).
The flux decreased slightly by (15±4)% to (1.20±0.05)×10-11 erg cm-2 s-1 in the 0.3-7.0 keV band.
In a 1948 s Swift/UVOT exposure with uvw1 filter (central wavelength: 260 nm),
no source is seen near the X-ray position, aside from 2MASS J00432709+4104521 (uvw1=15.34±0.05 mag, 5.7" angular separation).
We estimate a 3σ upper limit of 20.6 mag (Vega system).
An XMM-Newton follow-up observation is scheduled from 2014-01-13 22:23 to 2014-01-14 05:44.
We encourage optical observations to identify the counterpart.
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.
