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Swift UV light curves of recent M 31 novae

ATel #4281; F. Hofmann, M. Henze, J. Greiner, W. Pietsch (Max-Planck-Institut fuer extraterrestrische Physik, MPE)
on 27 Jul 2012; 09:51 UT
Credential Certification: Wolfgang Pietsch (wnp@mpe.mpg.de)

Subjects: Ultra-Violet, Nova, Transient, Variables

Referred to by ATel #: 4757, 6564

In the latest monitoring observations of the central region of the Andromeda Galaxy with the Ultra-violet/Optical Telescope (UVOT) on board the Swift satellite from 2012-05-24.62 UT to 2012-07-19.09 UT, we observe five recently discovered novae and one apparent UV variable. For all observations the UVOT uvw1 filter (181-321nm) is used. The following table shows UVOT uvw1 magnitudes (Vega system) and 1&sigma errors for each observed M 31 nova (see identification at the top of each column). Where the nova is not detected we give 3&sigma upper limits (identified by '>') and where there is no entry in the table, the nova is outside the detector field of view (FOV). We give the last two digits of the observation identification number (00035336000 + ID) and the Modified Julian Date (MJD) for the start of each observation. For observation 00035336052, nova M31N 2012-03b is only in the FOV of one pointing, so we only extract the magnitude from this one pointing instead of the added image of all pointings (marked by '*'). In observations 00035336056 and 00035336058 we have to exclude one pointing each due to attitude problems of the satellite.

  
ID  MJD       2012-03b  2012-05a  2012-05b  2012-06a  2012-06g 
 
52  56071.62 *18.6±0.2  17.5±0.1  17.0±0.1 >20.9     >20.3 
53  56079.77  18.4±0.1  17.5±0.1  17.8±0.1 >20.9     >20.3 
54  56087.26            17.8±0.1  17.6±0.1 >20.5     >19.9 
55  56095.14  18.4±0.1  18.2±0.1  17.1±0.1 >20.5     >19.9 
56  56103.03 		18.2±0.1  18.0±0.1  18.0±0.1  18.8±0.3 
58  56117.80  19.8±0.4  19.0±0.3  17.8±0.1  17.7±0.1  17.8±0.1 
60  56123.48 >20.1	18.5±0.2  17.3±0.1  17.9±0.1  18.2±0.2 
61  56127.09  19.4±0.2  19.0±0.2  17.2±0.1  18.2±0.1  18.6±0.2 
 


M31N 2012-03b, which was discovered on 2012-03-16.76 UT (ATel #3976) is still visible and fades after the observation of July 17. The UV magnitude of M31N 2012-05a (ATel #4096) continuously decreases. M31N 2012-05b (ATel #4096) shows a significant variability, since its brightness declines about 1 mag during the first 32 days and then increases by 0.8 mag in the following 24 days. Both M31N 2012-06a (ATel #4186) and M31N 2012-06g (PNV J00423991+4126573 on http://www.cbat.eps.harvard.edu/unconf/tocp.html) are first detected while still brightening and begin to fade from the observation of July 15 onwards.

The UV variable is detected in the UVOT images of observation 00035336061 (2012-07-19.09 UT) at the position RA = 00h42m39.91s, Dec=+41d14'35.6" (J2000, position error 0.2"). The position coincides with that of M31N 2011-10f (TCP J00423987+4114355) within the errors, indicating a new outburst only 288 days after the first detection (ATel #3712). The new outburst is further evidence that this source is not a nova, as already suggested in ATel #3755. Spectroscopy of this object is encouraged to identify its nature.

All magnitudes are on the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) and have not been corrected for extinction. 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.