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Spectroscopic classification of M31N 2016-08d as a luminous Fe II nova

ATel #9411; S. C. Williams (Lancaster), M. J. Darnley (LJMU), J. R. Thorstensen (Dartmouth), J. A. Klusmeyer (MDM Observatory), A. W. Shafter (SDSU), M. Henze (CSIC-IEEC), K. Hornoch (Ondrejov), K. Chinetti (Caltech)
on 25 Aug 2016; 22:57 UT
Credential Certification: Steven Williams (scw@astro.ljmu.ac.uk)

Subjects: Optical, Nova, Transient

We obtained the first spectrum of the luminous classical nova candidate M31N 2016-08d (PNV J00422352+4117197; see TNS, ATels #9388, #9408) on 2016 Aug 20.49 UT with the OSMOS spectrograph on the MDM 2.4m Hiltner Telescope (resolution R ~ 1600). The nova candidate was first detected on 2016 Aug 17.102 UT (ATel #9388). The spectrum shows Hα emission with a strong P-Cygni absorption component. We also detect Hβ in absorption, along with the Si II doublet at 6347/6371 Å and the Fe II 42 and 49 multiplets, again in absorption.

On Aug 22.06 we obtained a spectrum with the SPRAT spectrograph (Piascik et al. 2014; resolution R ~ 350) on the 2m Liverpool Telescope (Steele et al. 2004). The spectrum shows Balmer and Na I (D) absorption lines, along with numerous Fe II absorption lines, including those of the 42, 48, 49 and 74 multiplets. We also detect several Si II absorption features (5041, 5056, 6347, 6371 Å). This spectrum of M31N 2016-08d is very similar to the spectrum of the luminous classical nova M31N 2015-09c (which reached R = 14.26 ± 0.06; ATel #8108) taken when it was at maximum (see ATel #8109).

We obtained another spectrum with the OSMOS spectrograph on Aug 22.47. This spectrum is similar to that taken 0.41 days earlier with SPRAT, with the Balmer, Na I, Fe II and Si II absorption lines still present. Here we are able to identify a weak emission component redward of the Hα absorption line (this is not detected in the LT spectrum, and is weaker with respect to the continuum than in the first OSMOS spectrum). The systemic velocity is consistent with that of M31. A further OSMOS spectrum, taken Aug 24.38, shows significant evolution with Balmer, Fe II and Na I all present in emission. The lines still show strong P-Cygni absorption components.

These spectroscopic observations, in conjunction with the photometry published in ATel #9408, confirm that M31N 2016-08d is a luminous classical nova in M31 and a member of the Fe II spectroscopic class.