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Spectroscopic Confirmation of M31N 2015-12a (PNV J00424161+4115223) as a Classical Nova

ATel #8441; S. C. Williams (LJMU), M. J. Darnley (LJMU)
on 19 Dec 2015; 17:21 UT
Credential Certification: Matt Darnley (M.J.Darnley@ljmu.ac.uk)

Subjects: Optical, Nova, Transient

We obtained a spectrum of nova candidate M31N 2015-12a (PNV J00424161+4115223; ATel #8430) with the low-resolution (R~350) SPRAT spectrograph on the 2m Liverpool Telescope (Steele et al. 2004) on 2015 December 18.92 UT.

The spectrum shows strong and broad Balmer emission, with the FWHM of Hα measured at ~3600 km/s. The spectrum is contaminated by the nearby globular cluster Bol 124, however a preliminary analysis reveals two further emission lines corresponding to either He I or Fe II (lines at 4922/4924 and 5016/5018 Å). There is also a broad emission feature peaking at around 4636 Å, which may be N III (4638 Å).

This spectrum confirms M31N 2015-12a is a classical nova eruption in M31. While we cannot unambiguously identify its spectroscopic type, the broad emission shows it is not a typical Fe II nova, but of either He/N or Fe IIb type (see Williams 1992).