ASASSN-18gb: Spectroscopic confirmation as a nova eruption in NGC 3109
ATel #11472; M. J. Darnley (LJMU), M. W. Healy (LJMU), S. C. Williams (Lancaster)
on 23 Mar 2018; 23:14 UT
Credential Certification: Matt Darnley (M.J.Darnley@ljmu.ac.uk)
Subjects: Optical, Nova, Transient
The discovery of the transient ASASSN-18gb was reported in ATel #11470 and it was described as most likely to be a nova eruption in the Local Group galaxy NGC 3109 - and probably the first nova discovered within that galaxy.
We obtained a series of three 600s spectra using the SPRAT (Piascik et al. 2014) instrument on the Liverpool Telescope (Steele et al. 2004). These spectra were taken in relatively poor conditions at an airmass of almost 2. They show a noisy continuum, which when combined show a clear detection of Hα through Hδ lines, each displaying the characteristic P Cygni profile seen during the early phase of a nova eruption. The Hα P Cygni has a terminal velocity of ~2000 km/s. There may be tentative evidence for He I and/or Na-D emission lines. But further spectra are strongly encouraged.
This spectrum strongly suggests that the initial classification in ATel #11470 is correct and this is a (the first) nova eruption to be observed in NGC 3109. The spectrum also indicates that this nova was caught on the rise, or at least around optical maximum.
