ASAS-SN Discovery of a Large Outburst From NGC5273 and SCAT Classification as a Likely Optical Changing-Look AGN
ATel #15281; J. T. Hinkle, T. de Jaeger, B. J. Shappee, C. Ashall, D. Desai, A. Do, A. V. Payne, M. A. Tucker (IfA, Hawai'i), K. Z. Stanek, C. S. Kochanek, T. A. Thompson, J. M. M. Neustadt (Ohio State), T. W.-S. Holoien (Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), Xinyu Dai (Oklahoma), S. Dong (KIAA-PKU), Katie Auchettl (University of Melbourne)
on 16 Mar 2022; 08:17 UT
Credential Certification: Jason Hinkle (jhinkle6@hawaii.edu)
Subjects: Optical, AGN, Black Hole
During normal operations of the All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al. 2014, Kochanek et al. 2017) a large increase in brightness was observed for the AGN NGC5273. NGC5273 has been classified as a Seyfert 1.9 by Osterbrock & Martel (1993), but with improved host-subtraction, Trippe et al. (2010) suggested that NGC5273 is better described as a Seyfert 1.5, consistent with the classifications of Ho et al. (1995) and Dahari & De Robertis (1988).
Because of the large flux increase, we obtained a follow-up spectrum with the Supernova Integral Field Spectrograph (SNIFS) on the University of Hawaii 88-inch telescope on 2022-03-11 as part of the Spectral Classification of Astronomical Transients (SCAT) program (ATel #11444). Relative to an archival SDSS spectrum taken in May 2006, the spectrum is bluer and shows significantly stronger broad (~4000 km/s) Balmer and He I lines, similar to those seen in Seyfert 1 galaxies.
The long-term ASAS-SN and Asteroid Terrestrial-impact Last Alert System (ATLAS; Tonry et al. 2018) light curves show that NGC5273 has been steadily increasing in brightness for ~650 days, with a current subtracted g-band magnitude of ~16 mag above the ASAS-SN reference image.
Based on the large flux increase and the presence of broad emission lines consistent with a Seyfert 1, we suggest that NGC5273 has likely changed type from a Seyfert 1.5 to a Seyfert 1. We have requested Swift follow-up and are obtaining follow-up spectroscopy. We encourage further follow-up of this source, particularly high S/N spectroscopy.
