Spectroscopic classification of AT2019avd/ZTF19aaiqmgl/eRASSt J082337+042303 as a NLSy1
ATel #13717; S. Gezari (UMd), S. Frederick (UMd), S. van Velzen (UMd), L. Tartaglia (OKC), J. Sollerman (OKC), A. Goobar (OKC), D. Perley (LMJU), S. Kulkarni (Caltech)
on 8 May 2020; 14:37 UT
Credential Certification: Suvi Gezari (suvi@astro.umd.edu)
Subjects: Optical, X-ray, AGN, Transient
Referred to by ATel #: 13718
We report an optical spectrum of the nuclear transient AT2019avd/ZTF19aaiqmgl, first detected by ZTF on 2019 Feb 09, and coincident with the ultra-soft X-ray transient eRASSt J082337+042303 detected by eROSITA/SRG on 2020 April 28 (ATel #13712). We obtained a spectrum with NOT/ALFOSC on 2019 Mar 15, and detect strong Balmer lines (FWHM ~ 1500 km/s), He I emission lines, and an Fe II complex, characteristic of a NLSy1 galaxy at z=0.0296. The [O III] line emission, however, is weak compared to normal NLSy1 galaxies, and is potentially a signature of a light-travel time delay for the narrow-line region to respond to the flaring continuum.
The large amplitude optical variability of this flaring NLSy1 is unique, however, and may be related to the new class of extreme flaring NLSy1 galaxies, including AT2018bgt/Gaia18bee (Trakhtenbrot et al. 2019) and AT2019pev/ZTF19abvgxrq (ATel #13127), although we do not see any evidence of He II or Bowen fluorescence line emission in this early spectrum. While we disfavor a TDE origin for this soft X-ray transient, further follow-up spectroscopy and multi-wavelength monitoring is encouraged to understand the nature of this extreme AGN variability in the optical, X-rays, and radio (ATel #13716).
