Faulkes Telescope South observations 8.3 days after the 2016 eruption of the recurrent nova LMCN 1968-12a

ATel #8616; M. J. Darnley (LJMU), S. C. Williams (Lancaster)
on 30 Jan 2016; 22:48 UT
Credential Certification: Matt Darnley (M.J.Darnley@ljmu.ac.uk)

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The discovery of the 2016 eruption of the LMC recurrent nova LMCN 1968-12a was announced in ATel #8578 and was later spectroscopically confirmed (ATel #8586). ATel #8587 reported early Swift observations of the eruption including UV spectroscopy and an early (non-SSS) X-ray detection. The unveiling of the SSS just 6.4 days after the discovery was reported in ATel #8615, such a short `turn-on' time is suggestive of a high white dwarf mass. This eruption is the fifth recorded following 1968 (Sievers 1970), 1990 (see Shore et al. 1991), 2002 and 2010 (for both see Mróz et al. 2014).

Here we report photometric and spectroscopic observations of the 2016 eruption obtained by the Spectral and FLOYDS instruments, respectively, on the 2m Faulkes Telescope South (Siding Spring Observatory, NSW, Australia) on 2016 January 29 UT. These observations took place approximately 8.3 days after the first detection (2016 Jan 21.21 UT; ATel #8578). The Spectral observations were conducted in the B and V-bands with exposure times of 3×180 seconds; preliminary photometry is reported below.

 
Date (UT)       Δt (days)  Photometry         
 
2016-Jan-29.45  8.24       V = 16.56 ± 0.01   	 
2016-Jan-29.61  8.40       V = 16.59 ± 0.01 
2016-Jan-29.67  8.46       V = 16.50 ± 0.02 
 
2016-Jan-29.44  8.23       B = 16.63 ± 0.03 
2016-Jan-29.61  8.40       B = 16.72 ± 0.03 
2016-Jan-29.67  8.46       B = 16.78 ± 0.04 

We obtained a series of 3×900 seconds FLOYDS spectra of the 2016 eruption on 2016 Jan 29.6 UT. The spectral range covers 3,200 Å to 1.1 μm at an approximate resolution of R ~ 500. The signal-to-noise of the combined spectrum is particularly low and only four emission lines are clearly visible, Hα, Hβ, He II (4684 Å), and possibly He I/He II (6678/6683 Å; although this could be sub-structure of the Hα line). The Hα line consists of a bright central peak with FWHM = 1,900 ± 100 km/s on top of a broader pedestal with FWZI ≅ 10,000 km/s. The general description of the lines visible in this spectrum is consistent with that reported in ATel #8586 however, the line profile of Hα now appears to be symmetric.

The photometric monitoring observations on Faulkes Telescope South will continue daily (weather permitting. But we encourage further ground-based follow-up, including spectroscopic observations, of this recurrent nova.