Swift UVOT light curves of recent M 31 nova candidates

ATel #5271; R. Sturm, W. Pietsch, F. Hofmann, J. Greiner (MPE, Germany)
on 13 Aug 2013; 16:28 UT
Credential Certification: Richard Sturm (rsturm@mpe.mpg.de)

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From monitoring observations of the central region of the Andromeda Galaxy with the Ultra-violet/Optical Telescope (UVOT) on board the Swift satellite from 2013-05-27 to 2013-08-07, we derived UV light curves (UVW1 filter, 181-321 nm) for four recently discovered nova candidates: M31N 2013-05a (PNV J00424351+4116196, ATel #5099), M31N 2013-05b (PNV J00425563+4114125, ATel #5091, #5123), M31N 2013-06a (PNV J00424894+4115163, ATel #5133), and M31N 2013-06b (PNV J00425987+4120379, ATel #5157, #5173). The following table gives the UVW1 magnitudes (Vega system) and 1σ statistical uncertainties. Candidate nova name and first detection of the outburst in the optical (in MJD) are indicated at the top of each column (see M 31 (apparent) optical nova catalogue and references therein). We identify the observation by the last three digits of the identification number (00035336 + ID) and give MJD at the observation start. 3σ upper limits ('>') are given for observations adjacent to a nova detection.

       
 ID  MJD        2013-05a     2013-05b     2013-06a     2013-06b 
                (56422.00)   (56439.15)   (56458.05)   (56466.02) 
102  56439.15   17.99±0.13   15.97±0.03                              
103  56440.96   18.27±0.18   17.64±0.06                              
104  56443.54   17.90±0.10   18.63±0.08   >20.62                 
105  56447.43   18.67±0.51   >19.25       >19.44                      
107  56455.57   18.61±0.19   >20.35       19.67±0.24   >21.25 
108  56463.30   19.07±0.33                17.66±0.09   >21.13 
109  56471.11   19.94±0.55                17.69±0.08   18.98±0.09    
110  56479.20   >19.91                    18.01±0.09   18.52±0.08 
111  56487.07                             18.25±0.11   17.86±0.08 
112  56495.08                             18.85±0.13   18.09±0.08 
113  56503.29                             19.52±0.20   18.80±0.09 
114  56511.11                             19.54±0.20   18.80±0.09 
 
 

For the magnitudes of M31N 2013-05a and M31N 2013-06a, we estimate the systematic uncertainties to 0.5 mag and 0.15 mag because of the small distance to the centre of M31 and a nearby source, respectively. For the other sources, the systematic uncertainties are 0.03 mag.
M31N 2013-05b faded rapidly by more than 2 mag in the UVW1 filter within 2 days after its detection, continuing the fast decline reported in ATel #5091. M31N 2013-06a and M31N 2013-06b reached the UVW1 maximum about 5 and 21 days after the first optical detection and then faded continuously, the former by 2 mag in roughly 50 days.

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.