SALT spectroscopic classification of ASASSN-19hl as dwarf nova

ATel #12613; E. Aydi (MSU), D. A. H. Buckley (SAAO), L. Chomiuk, A. Kawash, K. Sokolovsky, J. Strader (MSU), K. Z. Stanek, C. S. Kochanek, J. Shields (OSU), B. J. Shappee (Univ. of Hawaii), D. Denisenko (SAI)
on 28 Mar 2019; 21:21 UT
Credential Certification: Elias Aydi (eaydi@saao.ac.za)

Tweet

We report on high-resolution optical spectroscopy of the transient ASASSN-19hl discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN: Shappee et al. 2014; Kochanek et al. 2017) on 2019-03-27.03 UT.

We obtained a 900 s spectrum of this object on 2019-03-28.38 UT, using the High Resolution Spectrograph (HRS; Crause et al. 2014, Proc. SPIE, 91476) mounted on the 11m Southern African Large Telescope. Observations were taken in the LR mode, covering a spectral range of 3800-8900 A; at a resolution of R=14000. The data were reduced with the SALT HRS MIDAS pipeline (Kniazev et al. 2016, MNRAS 459, 3068).

The spectrum shows a blue continuum with Balmer, He I, and He II emission on top of a broad absorption components. The emission profiles of the Balmer and He II lines are characterized by a double peak at radial velocities of -165 +/-5 km/s and +245 +/-5 km/s. The FWHMs of the blueshifted and redshifted emission components are around 305 +/- 10 km/s and 275 +/- 10 km/s, respectively. The overall spectrum is characteristic of a dwarf nova outburst.

The EW of the Na I D interstellar absorption doublet indicates low extinction towards the source (Av ~ 0.06), considerably lower than the total Galactic value (Av ~ 2.2) in this direction (Schlafly & Finkbeiner 2011, ApJ, 737, 103). This indicates that the dwarf nova is nearby, in agreement with the high optical brightness of the outburst, its white color reported in vsnet-alert #23090 and the parallax of the likely Gaia counterpart, which place the system at a distance of 320 +/- 40 pc.

 
Line identifications: 
H I : 4102, 4340, 4861, and 6563 A 
He I: 4388 A 
He II: 4686 A