A New Class of Changing-look LINERs

Sara Frederick, Suvi Gezari, Matthew J. Graham, S. Bradley Cenko, Sjoert Van Velzen, Daniel Stern, Nadejda Blagorodnova, Shrinivas R. Kulkarni, Lin Yan, Kishalay De, U. Christoffer Fremling, Tiara Hung, Erin Kara, David L. Shupe, Charlotte Ward, Eric C. Bellm, Richard Dekany, Dmitry A. Duev, Ulrich Feindt, Matteo GiomiThomas Kupfer, Russ R. Laher, Frank J. Masci, Adam A. Miller, James D. Neill, Chow Choong Ngeow, Maria T. Patterson, Michael Porter, Ben Rusholme, Jesper Sollerman, Richard Walters

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

We report the discovery of six active galactic nuclei (AGNs) caught "turning on" during the first nine months of the Zwicky Transient Facility (ZTF) survey. The host galaxies were classified as low-ionization nuclear emission-line region galaxies (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 AGNs, reminiscent of the changing-look LINER iPTF16bco. In one case, ZTF18aajupnt/AT2018dyk, follow-up Hubble Space Telescope ultraviolet and ground-based optical spectra revealed the transformation into a narrow-line Seyfert 1 with strong [Fe vii, x, xiv] and He ii λ 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.

Original languageEnglish (US)
Article number31
JournalAstrophysical Journal
Volume883
Issue number1
DOIs
StatePublished - Sep 20 2019

Keywords

  • accretion, accretion disks
  • galaxies: active
  • galaxies: nuclei
  • quasars: emission lines
  • relativistic processes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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