Swift UVOT discovery of a M 31 nova candidate
ATel #5256; >R. Sturm, W. Pietsch, F. Hofmann, J. Greiner (MPE, Germany)
on 7 Aug 2013; 16:01 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Richard Sturm (firstname.lastname@example.org)
Subjects: Ultra-Violet, Nova, Transient
Referred to by ATel #: 5260
We report the discovery of a UV-transient (PNV J00422137+4113004)
in a monitoring observation of the central region of the Andromeda Galaxy (M 31)
with the Ultra-violet/Optical Telescope (UVOT) on board the Swift satellite (ObsID 00035336114, starting 2013-08-07.11 UT).
The source is located at RA 00h 42m 21.37s, Dec +41d 13' 00.4" (J2000, ePos=0.5", 90% confidence level).
Light curve information is given in the table below (Vega system, 1σ statistical uncertainties).
A 3σ upper limit is derived from the last M 31 Swift observation before the detection.
All magnitudes are on the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) and have not been corrected for extinction.
ObsID MJD Exp uvw1
00035336113 56503.287 3936 >20.64
00035336114 56511.106 1336 16.31±0.03
00035336114 56511.173 1396 16.24±0.03
00035336114 56511.367 1354 16.39±0.03
The source 2MASS 00422116+4113007 (angular separation: 2.3", Ks
=15.9 mag) is unlikely related to the transient
and the outburst duration (>6.2 h) is atypical for a flare of a Galactic star.
There is no report of a recent detection of an optical nova or a historical nova (see http://www.mpe.mpg.de/~m31novae/opt/m31/M31_table.html
) for the position of the transient.
Because many UV transients in M 31 have been identified with optical novae in M 31, also with UV emission preceding the optical detection (see e.g. ATels #2713
, and #3061
the transient is likely explained by a new nova in M 31.
In order to investigate the nature of the newly detected UV transient, spectroscopic observations in the optical are encouraged.
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.