Liverpool Telescope Spectroscopy of ASASSN-17hx

ATel #10542; S. C. Williams (Lancaster), M. J. Darnley (LJMU)
on 29 Jun 2017; 15:26 UT
Credential Certification: Steven Williams (scw@astro.ljmu.ac.uk)

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ASASSN-17hx was discovered on 2017 Jun 19.41 (ATel #10523, #10524) and low-resolution spectroscopy was obtained on Jun 24.0 (ATel #10527). Here we report higher resolution spectroscopy (R ~ 5400) using 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.

Our most recent spectra were taken 2017 Jun 29.02 UT. They show strong Balmer and He I emission features, as identified in ATel #10527. We measure the FWHM of Hα to be 800 km/s. The Balmer and He I lines have a P Cygni absorption component, as does O I 7774 Å. The Hβ and Hγ absorption lines have shown two components, on Hβ we measure the minima of the two components to be at -860 km/s and -520 km/s on Jun 29.02. Between Jun 26.10 and Jun 29.02 the higher velocity absorption component became progressively weaker and the lower velocity component progressively stronger. In addition to the above features we identify emission from Mg II (4481, 7896 Å) and Si II (6347, 6371 Å). There are also emission lines at around 6242, 6829 and 7042 Å, which we attribute to most likely Al II 6237, 6830 and 7049 Å, the latter of which is blended with the absorption component of He I 7065 Å.

We have UV spectroscopy of ASASSN-17hx planned on Swift and encourage further follow-up.