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Spectroscopic classification of M31N 2015-12c (PNV J00383650+3939536) as a classical nova in the outer regions of M31

ATel #8622; S. C. Williams (Lancaster), M. J. Darnley (LJMU)
on 1 Feb 2016; 20:36 UT
Credential Certification: Steven Williams (scw@astro.ljmu.ac.uk)

Subjects: Optical, Nova

We obtained a spectrum of nova candidate M31N 2015-12c (PNV J00383650+3939536, CSS151229:003837+393954; see CBAT TOCP and CCS) with the SPRAT spectrograph on the 2m Liverpool Telescope (Steele et al. 2004) on 2016 January 26.84 UT.

The spectrum shows strong Balmer emission, with the Fe II 42 triplet also clearly identified in emission. We measure the FWHM of the Hα line to be ~ 1500 km/s. A number of further lines are visible in the spectrum, including Na I (D), O I (7774 Å), [O I] (6300 and 6364 Å), N III (4638 Å) and C II (7235 Å). This spectrum confirms that M31N 2015-12c is a classical nova eruption and is consistent with it being a member of the Fe II spectroscopic class. Our spectrum was taken about 28 days post-discovery, and is consistent with the nova being significantly beyond its optical peak.

Nova M31N 2015-12c is at a large distance from the centre of M31, with the apparent offset being 107 arcmin (at the distance of M31 this corresponds to ~24 kpc). Comparing this to other novae from the Pietsch et al. database shows it has one of the largest offsets of all spectroscopically confirmed novae in M31, with only M31N 2008-08d (Yuan et al. 2009, Shafter et al. 2011, ATels #1702, #1708) and M31N 2011-06e (ATel #3498) at larger apparent radii.