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Swift UVOT detection of the recurrent nova M31N 1990-10a during its 2016 eruption

ATel #9280; M. Henze (CSIC-IEEC), S. C. Williams (Lancaster), M. J. Darnley (LJMU), A. Ederoclite (CEFCA), G. Sala (UPC-IEEC), A. W. Shafter (SDSU), K. Hornoch (Ondrejov)
on 30 Jul 2016; 08:55 UT
Credential Certification: Martin Henze (henze@ice.cat)

Subjects: Ultra-Violet, Nova, Transient

Referred to by ATel #: 9281, 9383, 9386, 9408, 9435, 10001

A new eruption of the M31 recurrent nova M31N 1990-10a was discovered recently on July 27 (see ATel #9276). The last observed eruption took place in 2007 (ATel #1131), which suggests a recurrence period of merely 8-9 years. Only four other M31 novae have known recurrence periods shorter than a decade (see Shafter et al. 2015 for a recent comprehensive review): M31N 1984-07a (~ 8 yr; ATel #4364), M31N 1963-09c (~5 yr; ATels #3001,#8234), M31N 1997-11k (~4 yr; ATels #2286,#2290) and the remarkable nova M31N 2008-12a (0.5 yr or 1 yr; see Darnley et al. 2016, Henze et al. 2015). Nova U Sco, the fastest Galactic recurrent nova, has an average recurrence period of 10 yr (Schaefer 2010). Short recurrence times indicate massive WDs that are promising type Ia supernova progenitors.

Here we report follow-up observations of M31N 1990-10a with the Swift satellite. A first 3.0-ks Swift pointing was obtained on 2016-07-29.64 UT (MJD 57598.64), which is 2.7 d after the (updated) estimated eruption date on 2016-07-26.98 UT (uncertainty of 0.5 d). The nova was clearly detected by the UVOT instrument with a uvw1 filter (Vega) magnitude of 17.6±0.1 mag (uvw1 central wavelength 260 nm). The magnitude is in the UVOT photometric system (Poole et al. 2008) and has not been corrected for extinction. Nothing is detected in the corresponding Swift XRT exposure. We will continue to monitor the UV and X-ray evolution of this fast recurrent nova.

We wish to thank the Swift Team for the rapid scheduling of the ToO observations, in particular N. Gehrels, the duty scientists as well as the science planners.