Optical Spectroscopy of Gamma-ray Nova Sco 2012 in the nebular stage
ATel #5525; A. W. Shaw (U. Southampton), P. A. Charles (U. Southampton), C. Knigge (U. Southampton), A. B. Hill (SLAC), P. Woudt (U. Cape Town) and B. Warner (U. Cape Town)
on 29 Oct 2013; 13:17 UT
Credential Certification: Christian Knigge (christian@astro.soton.ac.uk)
Subjects: Optical, Binary, Cataclysmic Variable, Nova, Transient
Referred to by ATel #: 5541
We report on recent optical spectroscopy of Nova Sco 2012, which was discovered in June 2012 as a bright transient in the galactic bulge by the Microlensing Observations in Astrophysics (MOA) Collaboration (ATel #4157) and subsequently detected in gamma-rays by the Fermi Gamma-ray Space Telescope (ATel #4284). Follow-up spectra revealed a standard Fe II nova (ATel #4287).
Our new spectroscopic observations were carried out on 2013 September 6 (20:10 - 20:40 UTC), using the Southern African Large Telescope and the Robert Stobie Spectrograph (RSS). We obtained 3x600s exposures from 4060-7120Å at 0.49Å/pixel with a central resolution of 5.7Å.
Our combined spectrum exhibits Fe II, O I and N I emission lines typical of an Fe II nova, as well as strong forbidden lines consistent with Nova Sco 2012 being in the nebular stage. The strongest lines are the [O III] 4959/5007Å lines followed by Hα. Other strong lines include [Fe VII] at 5721 and 6086Å. Hβ is also present, though only at ~3.5% the strength of Hα. Also detected are the N III 4640Å fluorescence feature and He II 4686Å, which we believe are indicative of the hot white dwarf.
Optical follow-up when the nova is again accessible is encouraged in order to confirm the putative binary period of ~1.6hr reported in ATel #4157.
