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Spectroscopy of ASASSN-17lg

ATel #10709; S. C. Williams (Lancaster), M. J. Darnley (LJMU), L. Chomiuk (Michigan St)
on 5 Sep 2017; 16:27 UT
Credential Certification: Steven Williams (scw@astro.ljmu.ac.uk)

Subjects: Optical, Cataclysmic Variable, Transient

ASASSN-17lg was discovered at magnitude V = 14.92 on 2017 August 27.24 UT (see ASAS-SN Transients page). We obtained a spectrum of the transient with the SPRAT spectrograph (resolution R ~ 350; Piascik et al. 2014) on the 2-m Liverpool Telescope (Steele et al. 2004) on 2017 September 2.85 UT.

The spectrum displays absorption lines from Hβ, Hγ and Hδ, which show no significant velocity shift. A Hα feature is also detected, which shows narrow emission in the centre of a broader absorption line. The only other feature clearly detected is Na I D absorption, although He I 4471 Å may also be present. This spectrum indicates ASASSN-17lg is a dwarf nova outburst.