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Spectroscopic classification of M33N 2016-12a (AT2016irp) as a classical nova

ATel #9828; S. C. Williams (Lancaster), M. J. Darnley (LJMU)
on 5 Dec 2016; 23:33 UT
Credential Certification: Steven Williams (scw@astro.ljmu.ac.uk)

Subjects: Optical, Nova, Variables

We obtained a spectrum of classical nova candidate M33N 2016-12a (AT2016irp; PNV J01340158+3042406; PNV J01340157+3042398) with the SPRAT spectrograph (resolution R ~ 350; Piascik et al. 2014) on the 2-m Liverpool Telescope (LT; Steele et al. 2004) on 2016 December 5.87 UT.

The spectrum shows strong Balmer emission lines (Hα, Hβ, Hγ, Hδ). Even at this low resolution, significant structure can be seen in the Balmer lines, which have a very broad base (FWZI of Hα is measured at ~ 9000 km/s). There is also a narrower component, which is approximately centred at the rest wavelength. Several He I emission lines are also seen (4471, 4922, 5016, 5048, 5876, 6678 and 7065 Å), with He I 5876 Å (the line with the highest S/N) also clearly displaying a similar structure to the Balmer lines. N III emission is seen at 4640 Å, which is blended with He II (4686 Å). Fe II 5169 Å (i.e. the only line of the Fe II 42 triplet not coincident with a He I line) also appears to be weakly present.

This spectrum confirms that M33N 2016-12a is a classical nova in M33 and a member of the He/N spectroscopic class. The spectra are somewhat similar to those seen in recurrent novae U Sco (e.g. Diaz et al. 2010) and LMC 1968 (Williams et al. 1991; ATel #8616) around a week after eruption. Further follow-up observations of this nova are encouraged.