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Spectroscopic Observations of a Recent M31 Nova Candidate Near Maximum Light

ATel #2898; A. W. Shafter (SDSU), R. Ciardullo (PSU), M. J. Darnley, M. F. Bode (Liverpool JMU, UK), K. A. Misselt (U. Arizona)
on 2 Oct 2010; 01:51 UT
Credential Certification: Allen W. Shafter (aws@nova.sdsu.edu)

Subjects: Optical, Nova, Transient

Referred to by ATel #: 2909

We report spectroscopic observations of the recent M31 nova candidate (M31OT 004345.5+410755; M31N 2010-09c?) discovered by Nishiyama and Kabashima (Miyaki-Argenteus Observatory, Japan) on 2010 Sep. 30.566 UT (private communication) and confirmed by Pietsch et al. (ATel #2896). At our request, a spectrum (410–950 nm) of the nova candidate was obtained less than a day post discovery on 2010 Oct. 01.39 UT with the Marcario Low-Resolution Spectrograph on the 9.2m Hobby-Eberly Telescope (HET), possibly while the object was still increasing in brightness. The photometric measurements by Pietsch et al. have shown that the object brightened from R=17.7 on Sep. 30.412 UT to R=16.6 on Oct. 01.180 UT, ~5 hours prior to our spectroscopic observations. At about the same time as their latter measurement, we obtained B and V photometry with the Liverpool Telescope. These observations establish that on Oct. 01.135 UT, V=16.777±0.006 and (B−V)=0.247±0.008 -- the color being typical of a nova near maximum light. Consistent with this, our HET spectrum reveals Balmer (FWHM H&alpha ~ 1600 km/s) and weak Fe II(42) emission features with pronounced P Cgyni profiles superimposed on a steep blue continuum. The absorption components are displaced by ~1500 km/s to the blue of the emission peaks. There is also a hint of weak He II &lambda 468.6 nm and N II &lambda 567.9 nm emission present in our data. Our spectroscopic observations confirm that this object is indeed a classical nova observed at or shortly before maximum light. Further, the data show that the nova is most likely a member of the Fe II spectroscopic class (Williams 1992, AJ, 104, 725), although given the early epoch of our observations and the possible detection of He II and N II, membership in the hybrid class cannot be ruled out at this time. Additional spectroscopic observations over the next week or so will be required to determine if the spectrum transitions into a He/N type as is characteristic of hybrid novae.

A.W.S. thanks the NSF for support through AST-0607682 and the University of Victoria for hospitality.