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Spectroscopic Confirmation and Provisional Classification of PNV J00424328+4117152 as a Bright He/N Nova in M31

ATel #10981; A. W. Shafter, M. Henze, A. S. Igarashi, J. Horst (SDSU), M. J. Darnley, (Liverpool JMU), S. C. Williams (U. Lancaster), and T. A. Rector (U. Alaska, Anchorage)
on 17 Nov 2017; 21:06 UT
Credential Certification: Allen W. Shafter (ashafter@mail.sdsu.edu)

Subjects: Optical, Nova, Transient

Referred to by ATel #: 10986, 11031

We report spectroscopic observations of the M31 nova candidate PNV J00424328+4117152 (tentatively identified as M31N 2017-11d?) discovered on 2017 Nov. 12.103 UT by Igarashi et al. (ATel #10955). The spectroscopic data were acquired by two of us (M. J. Darnley and S. C. Williams) using the SPRAT on the Liverpool Telescope during the nights of 2017 Nov. 14.877 and Nov. 16.924 (approximately 3 and 5 days post eruption). The first spectrum is characterized by strong (EW Hα = -38±4 nm) and broad (FWHM Hα = 4500±200 km/s) Balmer emission superimposed on a relatively flat continuum. There is some evidence for a narrower emission component to the Hα line, along with weak but broad emission features consistent with identification as N II λ500.1 nm and the Bowen blend (C III/N III) near λ464.0 nm. In addition, there appear to be emission features near λ450.0 and λ698.0 nm where the identifications remain ambiguous. In the second spectrum from two days later, the Balmer lines have narrowed somewhat (FWHM Hα = 3700±200 km/s), the N II and N III lines at λ500.1 and λ464.0 nm appear to have weakened, while the unidentified lines from two days earlier have disappeared. Finally, there is a hint of weak emission longward of Hβ, which could possibly be identified with either Fe II or He I.

These latest observations confirm that PNV J00424328+4117152 is indeed a nova in M31. The presence of the broad Balmer and Nitrogen emission lines in the first spectrum strongly suggest that the nova is a member of the He/N spectroscopic class (e.g., see Williams 1992, AJ, 104, 725); however, the weakening of the N II and N III lines along with the possible emergence of Fe II lines longward of Hβ in the second spectrum make a Hybrid classification a possibility. Further spectroscopic observations are encouraged in order to follow the evolution of this bright nova, and to confirm the spectroscopic classification.