Recurrent Nova M31N 2008-12a: Liverpool Telescope SPRAT Spectrum
ATel #6540; M. J. Darnley (LJMU), I. A. Steele (LJMU), R. J. Smith (LJMU), A .W. Shafter (SDSU), M. F. Bode (LJMU), A. S. Piascik (LJMU), S. C. Williams (LJMU), M. Henze (ESAC), J.-U. Ness (ESAC), R. A. Hounsell (STSCI)
on 4 Oct 2014; 22:17 UT
Credential Certification: Matt Darnley (M.J.Darnley@ljmu.ac.uk)
The recent detection of a sixth optical eruption of the M31 recurrent nova M31N 2008-12a (ATel #6527, #6532, #6535) was spectroscopically confirmed by iPTF (ATel #6537).
The 2m fully robotic Liverpool Telescope (LT, Steele et al. 2004) observed the eruption with its new, low dispersion, high throughput spectrograph 'SPRAT' (SPectrograph for the Rapid Acquisition of Transients; Piascik et al. 2014).
Each of a series of LT SPRAT spectra of M31N 2008-12a taken between 2014 Oct 3.928 UT and Oct 4.213 UT shows features that are consistent with those reported in ATel #6537. These spectra are remarkably similar to the spectrum of M31N 2008-12a following its 2012 eruption (aka M31N 2012-10a; see ATel #4503 and Darnley et al. 2014).
The SPRAT spectra are dominated by Hydrogen Balmer series emission lines (Hα, Hβ, Hγ, and Hδ). The following emission lines are also present, He I (4471, 5017, 5876, 6678, 7065), N II (5001, 5680), and N III (4641). The N I (6485) and Si II (6347, 6371) emission lines may also be present. We measure the FWHM of the Hα and Hβ emission lines to be 2,500 ± 100 km/s and 2,200 ± 100 km/s, respectively.
The spectra of the 2014 eruption of M31N 2008-12a are consistent with a He/N nova, although the emission lines are not as broad as those typically associated with this spectral class of nova.