Liverpool Telescope spectroscopy of the 2018 outburst of GK Per
ATel #11995; S. C. Williams (Lancaster), M. J. Darnley (LJMU)
on 29 Aug 2018; 13:59 UT
Credential Certification: Steven Williams (scw@astro.ljmu.ac.uk)
Subjects: Optical, Cataclysmic Variable, Nova, Transient
Referred to by ATel #: 15858
GK Per is currently undergoing a dwarf nova outburst (AAVSO Alert Notice 649). GK Per underwent a classical nova eruption in 1901 (Pickering 1901, Hale 1901). We obtained a spectrum of the current outburst with the FRODOSpec spectrograph (Barnsley et al. 2012) on the 2-m Liverpool Telescope (Steele et al. 2004), with a wavelength coverage of 3900 to 5100 Å and 5900 to 8000 Å and resolution of R ~ 5400, on 2018 Aug 29.17 UT.
The spectrum shows strong Balmer emission lines (Hα, Hβ, Hγ, Hδ, Hε). We measure the FWHM to be 540+/-30 km/s for Hα, 540+/-30 km/s for Hβ and 500+/-30 km/s for Hγ. The spectrum also shows strong emission from He II 4686 Å, which may be slightly broader at FWHM = 610+/-30 km/s. These velocities are similar to those seen during the 2015 outburst (ATel #7217). We see several He I lines, including 4388, 4471, 4922, 5016, 6678, 7065 Å. The highest S/N He I lines (6678 and 7065) clearly show a double-peaked structure (evidence for this can also be seen in the other He I lines), unlike the He II line, which is relatively well described by a Gaussian profile. The Balmer lines do not show a clear double peak, but they are somewhat asymmetric. We also identify weaker features of OI (7773 Å) and N III (4638 Å).
