Spectroscopy of M31N 2007-11g: Another Luminous Mira-like Variable in M31 Masquerading as a Nova
ATel #1851; A. W. Shafter (SDSU); R. Ciardullo (PSU); V. Burwitz, M. Henze and W. Pietsch (MPE); P. Milne, K. A. Misselt and G. Williams (U. Arizona); D. H. Hartmann and A. Updike (CU); M. F. Bode and M. J. Darnley (Liverpool JMU)
on 21 Nov 2008; 23:58 UT
Credential Certification: Allen W. Shafter (email@example.com)
Subjects: Optical, Nova, Transient, Variables
On 2008 November 17.23 UT observations made with the
Livermore Optical Transient Imaging System
(Super-LOTIS, located at Steward Observatory, Kitt Peak, Arizona, USA)
revealed that the nova candidate M31N 2007-11g
(Ovcharov et al. 2007; Atel #1312) had re-brightened to R~18.8,
similar to its brightness at discovery a year earlier in November 2007.
Since this behavior would be unusual for a nova (but typical
of a Long-Period Variable), we decided to
obtain a spectrum of M31N 2007-11g to determine its nature.
On 2008 November 18.3 UT, we observed M31N 2007-11g with the
Marcario Low-Resolution Spectrograph on the 9.2-m Hobby Eberly
Telescope. The spectrum reveals strong TiO absorption bands and
narrow Balmer emission (H&alpha: FWHM ~ 300 km/s; EW ~ -10Ã
; RV ~ -275 km/s) superimposed on a red continuum.
Thus, as suspected, M31N 2007-11g is not a nova; but rather
appears to be a luminous
long-period Mira-like variable, similar to the nova candidate M31N 1995-11e
(Shafter et al. 2008; Atel #1834).