A New Class of Changing-Look LINERs
Abstract
We report the discovery of six active galactic nuclei (AGN) caught "turning on" during the first nine months of the Zwicky Transient Facility (ZTF) survey. The host galaxies were classified as LINERs by weak narrow forbidden line emission in their archival SDSS spectra, and detected by ZTF as nuclear transients. In five of the cases, we found via follow-up spectroscopy that they had transformed into broad-line AGN, reminiscent of the changing-look LINER iPTF 16bco. In one case, ZTF18aajupnt/AT2018dyk, follow-up HST UV and ground-based optical spectra revealed the transformation into a narrow-line Seyfert 1 (NLS1) with strong [Fe VII, X, XIV] and He II 4686 coronal lines. Swift monitoring observations of this source reveal bright UV emission that tracks the optical flare, accompanied by a luminous soft X-ray flare that peaks ~60 days later. Spitzer follow-up observations also detect a luminous mid-infrared flare implying a large covering fraction of dust. Archival light curves of the entire sample from CRTS, ATLAS, and ASAS-SN constrain the onset of the optical nuclear flaring from a prolonged quiescent state. Here we present the systematic selection and follow-up of this new class of changing-look LINERs, compare their properties to previously reported changing-look Seyfert galaxies, and conclude that they are a unique class of transients well-suited to test the uncertain physical processes associated with the LINER accretion state.
Cite
@article{arxiv.1904.10973,
title = {A New Class of Changing-Look LINERs},
author = {Sara Frederick and Suvi Gezari and Matthew J. Graham and S. Bradley Cenko and Sjoert van Velzen and Daniel Stern and Nadejda Blagorodnova and Shrinivas R. Kulkarni and Lin Yan and Kishalay De and U. Christoffer Fremling and Tiara Hung and Erin Kara and David L. Shupe and Charlotte Ward and Eric C. Bellm and Richard Dekany and Dmitry A. Duev and Ulrich Feindt and Matteo Giomi and Thomas Kupfer and Russ R. Laher and Frank J. Masci and Adam A. Miller and James D. Neill and Chow-Choong Ngeow and Maria T. Patterson and Michael Porter and Ben Rusholme and Jesper Sollerman and Richard Walters},
journal= {arXiv preprint arXiv:1904.10973},
year = {2019}
}
Comments
Submitted to ApJ, 31 pages, 17 Figures (excluding Appendix due to file size constraints but will be available in electronic version)