Erratum to ATel #9347
ATel #9351; K. Chinetti (Caltech), M. J. Darnley (LJMU), N. Blagorodnova (Caltech), J. D. Neill (Caltech), S. C. Williams (Lancaster)
on 9 Aug 2016; 17:36 UT
Credential Certification: Matt Darnley (M.J.Darnley@ljmu.ac.uk)
Subjects: Optical, Nova, Transient
In ATel #9347, we reported the discovery of a new classical nova in M31. However, discovery of this particular nova, M31N 2016-07c (PNV J00435768+4134528 / PNV J00435778+4134528), had already been reported by K. Nishiyama & F. Kabashima (see CBAT TOCP). Follow-up photometry was reported in ATel #9264, and indeed spectroscopic confirmation had already been reported by some of these authors in ATel #9296. Also see the Rochester Astronomy site.
We also note that all other information reported in ATel #9347 is correct, including the photometry and the (now) follow-up spectroscopy.
Part of our confusion regarding this object has been caused by the somewhat unusual photometric development of this nova.
The light curve (see link at bottom) shows a prominent re-brightening around 10 days after the original detection. Within the first 5 days post-discovery, this nova appears to have faded by around 2 magnitudes, before re-brightening by around 1.5 magnitudes over the second period of 5 days. In the subsequent 10 days, the nova brightness has remained approximately constant. (Note the LT+SPRAT data point is taken through an unusual V+R filter, hence there may be a sizeable systematic uncertainty associated with that data point.)
Similar re-brightenings have been recorded in a number of Galactic novae, and have been proposed to be related to additional periods of large mass loss from the system, often accompanied by a series of 'nested' P Cygni profiles in the spectra.
The first spectrum of this nova (ATel #9296) was taken during the first minimum of the light curve, the subsequent spectra (ATel #9347) are consistent with the first spectrum, although of higher signal-to-noise. The later spectra also confirm (unreported) tentative Fe II line identifications from first spectrum (ATel #9296).
We are extremely grateful to David Bishop for pointing out our original oversight!
M31N 2016-07c light curve
