Spectroscopic observation of a dwarf nova superoutburst ZTF19abgsssu
ATel #12980; Monika Soraisam (NOAO), Chien-Hsiu Lee (NOAO), Gautham Narayan (STScI), Thomas Matheson (NOAO), Abhijit Saha (NOAO), Arizona-NOAO Temporal Analysis and response to Events System (ANTARES) team, Thomas G. Brink, Kishore C. Patra, Thomas de Jaeger, WeiKang Zheng, Benjamin E. Stahl, Alexei V. Filippenko (UC Berkeley), Howard E. Bond (Penn State, STScI)
on 2 Aug 2019; 06:27 UT
Credential Certification: Monika Soraisam (soraisam@noao.edu)
Subjects: Optical, Cataclysmic Variable, Nova, Transient
We report the spectroscopic observation of ZTF19abgsssu, which was flagged by a filter on the ANTARES alert-broker (https://antares.noao.edu/) customized to find transients in the public alert stream of the ZTF survey. The source is located at RA 20h16m16.71s, DEC +18d22m25.40s (J2000). It was first detected by ZTF on 18 July 2019 (MJD 58683.235891) with R = 14.78 +/- 0.02 mag, preceded by non-detections, the latest of which was on 14 July 2019. It rapidly declined by around 3 mag in 13 days and currently it is at R = 17.48 +/- 0.06 and g = 17.36 +/- 0.05 mag (1 August 2019).
On 27 July 2019, we obtained a spectrum of this source with the Kast double spectrograph on the Shane 3 m telescope at Lick Observatory. The spectrum shows higher-order Balmer lines in absorption, with H-beta showing an emission core, typical of dwarf novae. However, it exhibits strong H-alpha emission, with the Balmer decrement H-alpha:H-beta around 48:1. The present outburst of the dwarf nova was also caught by ASAS-SN on 19 July 2019. Investigating the light curve of this source in the ASAS-SN sky portal between 2015 and now, we do not find any such high-amplitude (super)outburst. This is likely a WZ Sge-type event.
The light curve of the source from ANTARES is at https://antares.noao.edu/alerts/locus/3620599.
