Swift UV light curves of novae M31N 2014-10a and 2014-11a; new outburst time and large-amplitude variation of 2014-11a

ATel #6759; C. Delvaux, J. Greiner, W. Pietsch, R. Sturm (Max -Planck-Institut fuer extraterrestrische Physik, MPE)
on 27 Nov 2014; 08:54 UT
Credential Certification: Wolfgang Pietsch (wnp@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 2014-10-01 to 2014-11-22, we derived UV light curves (UVW1 filter, 181-321 nm) for two recently discovered novae: M31N 2014-10a (ATel #6563) and 2014-11a (ATel #6675), The following table gives the observation ID, the exposure time, the date and start time of the observations, UVW1 magnitudes (Vega system) and 1σ statistical uncertainties for M31N 2014-10a and 2014-11a.

 
ObsID        Exp      Date           Time             2014-10a        2014-11a 
             [ks]                    (MJD)            mag(Vega)       mag(Vega) 
00032702081  1.3      2014-10-01     56931.96          <22.77 
00031283010  1.3      2014-10-21     56947.57          <20.06 
00031283011  2.2      2014-10-25     56951.35        19.88±0.23 
00031283012  3.9      2014-10-29     56955.75        19.61±0.15 
00031283014  3.1      2014-11-02     56963.76        19.81±0.19        <19.86 
00031283015  1.7      2014-11-06     56967.74        19.76±0.24      18.97±0.22 
00031283016  3.9      2014-11-10     56971.60        19.62±0.15      18.48±0.10 
00031283017  4.0      2014-11-14     56975.53        18.89±0.08      19.49±0.23 
00031283018  4.3      2014-11-18     56979.34        18.86±0.08      18.28±0.08 
00031283019  4.1      2014-11-22     56983.38        19.44±0.13      18.13±0.07 

The systematic uncertainty of these magnitudes is estimated to be 0.03 mag.

M31N 2014-10a was only detected in the UV 15d after the optical detection, which is consistent with the conclusion of ATel #6616 that the nova stayed for some time in an optical thick stage. The nova seems to have reached its maximum in the UVW1 filter around 2014-11-16 and appears to be fading afterwards.

M31N 2014-11a has been detected by Swift/UVOT before the first reported optical detection at MJD 56968.98 (see ATel #6675). The upper limit on 2014-11-02 constrains the outburst time to Nov 2-6. The nova faded in the filter UVW1 at the same time as reported in the optical (ATel #6704), however, to reach an even brighter level afterwards.

We strongly encourage new observations of M31N 2014-11a to check for a similar behavior in the optical.

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.