Investigating the Nature of the Luminous Ambiguous Nuclear Transient ASASSN-17jz

Creators: Holoien, Thomas W.-S.; Neustadt, Jack M. M.; Vallely, Patrick J.; Auchettl, Katie; Hinkle, Jason T.; Romero-Cañizales, Cristina; Shappee, Benjamin. J.; Kochanek, Christopher S.; Stanek, K. Z.; Chen, Ping; Dong, Subo; Prieto, Jose L.; Thompson, Todd A.; Brink, Thomas G.; Filippenko, Alexei V.; Zheng, WeiKang; Bersier, David; Bose, Subhash; Burgasser, Adam J.; Channa, Sanyum; de Jaeger, Thomas; Hestenes, Julia; Im, Myungshin; Jeffers, Benjamin; Jun, Hyunsung D.; Lansbury, George; Post, Richard S.; Ross, Timothy W.; Stern, Daniel; Tang, Kevin; Tucker, Michael A.; Valenti, Stefano; Yunus, Sameen; Zhang, Keto D.

Abstract

We present observations of the extremely luminous but ambiguous nuclear transient (ANT) ASASSN-17jz, spanning roughly 1200 days of the object's evolution. ASASSN-17jz was discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) in the galaxy SDSS J171955.84+414049.4 on UT 2017 July 27 at a redshift of z = 0.1641. The transient peaked at an absolute B-band magnitude of M_(B,peak) = −22.81, corresponding to a bolometric luminosity of L_(bol,peak) = 8.3 × 10⁴⁴ erg s⁻¹, and exhibited late-time ultraviolet emission that was still ongoing in our latest observations. Integrating the full light curve gives a total emitted energy of E_(tot) = (1.36 ±0.08) × 10⁵² erg, with (0.80 ± 0.02) × 10⁵² erg of this emitted within 200 days of peak light. This late-time ultraviolet emission is accompanied by increasing X-ray emission that becomes softer as it brightens. ASASSN-17jz exhibited a large number of spectral emission lines most commonly seen in active galactic nuclei (AGNs) with little evidence of evolution. It also showed transient Balmer features, which became fainter and broader over time, and are still being detected >1000 days after peak brightness. We consider various physical scenarios for the origin of the transient, including supernovae (SNe), tidal disruption events, AGN outbursts, and ANTs. We find that the most likely explanation is that ASASSN-17jz was a SN IIn occurring in or near the disk of an existing AGN, and that the late-time emission is caused by the AGN transitioning to a more active state.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 September 15; revised 2022 May 6; accepted 2022 May 26; published 2022 July 14. The authors thank Y. Chen, J. Mauerhan, C. Melis, C. C. Steidel, and R. L. Theios for obtaining follow-up data. We thank Lizelke Klindt and Fiona Harrison for contributing to observations made with the Palomar 200 inch telescope. U.C. Berkeley students Nick Choksi, Edward Falcon, Romain Hardy, Goni Halevy, Emily Ma, Yukei Murakami, Jackson Sipple, Costas Soler, Samantha Stegman, James Sunseri, Sergiy Vasylyev, and Jeremy Wayland contributed to observations with the Lick Nickel 1 m telescope. We are grateful to S. Gomez for assistance with running MOSFiT SN models. We thank the Swift PI, the Observation Duty Scientists, and the science planners for promptly approving and executing our Swift observations. The Las Cumbres Observatory and its staff are gratefully acknowledged for their continuing assistance with the ASAS-SN project. We thank the staffs of the various observatories where data were obtained for their assistance. ASAS-SN is supported by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University and National Science Foundation (NSF) grant AST-1515927. Development of ASAS-SN has been supported by NSF grant AST-0908816, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics at the Ohio State University, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), the Villum Foundation, and George Skestos. Support for T.W.-S.H. was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51458.001-A awarded by the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. P.J.V. is supported by the National Science Foundation Graduate Research Fellowship Program Under grant No. DGE-1343012. C.R.-C. acknowledges financial support from the Chinese Academy of Sciences (CAS), through the CAS South America Center for Astronomy (CASSACA) and CONICYT grant CAS16013. K.Z.S., C.S.K., and T.A.T. are supported by NSF grants AST-1515876, AST-1515927, and AST-1814440. B.J.S., C.S.K., and K.Z.S. are supported by NSF grant AST-1907570/AST-1908952. B.J.S. is also supported by NSF grants AST-1920392 and AST-1911074. Support for J.L.P. and C.R.-C. is provided in part by ANID through the Fondecyt regular grant 1191038 and through the Millennium Science Initiative grant ICN12009, awarded to The Millennium Institute of Astrophysics (MAS). T.A.T. is supported in part by NASA grant 80NSSC20K0531. A.V.F.'s supernova research group at U.C. Berkeley has been supported by the TABASGO Foundation, Gary and Cynthia Bengier (T.d.J. was a Bengier Postdoctoral Fellow), the Christopher R. Redlich Fund, the Miller Institute for Basic Research in Science (A.V.F. is a Miller Senior Fellow), NASA/HST grant GO-15166 from STScI, and Google (K.D.Z. was a Google/Lick Predoctoral Fellow). M.I. acknowledges the support from the National Research Foundation (NRF) grants 2020R1A2C3011091 and 2021M3F7A1084525, supervised by the Ministry of Science and ICT (MSIT) of Korea. H.D.J. is supported by the NRF grant 2022R1C1C2013543 funded by the MSIT of Korea. M.A.T. acknowledges support from the Department of Energy Computational Science Graduate Fellowship through grant DE-SC0019323. Research by S.V. is supported by NSF grants AST-1813176 and AST-2008108. Parts of this research were supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Advanced Scientific Computing Research, Department of Energy Computational Science Graduate Fellowship under award No. DE-FG02-97ER25308. This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from STScI, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 526555. These observations are associated with programs HST-GO-14781, HST-GO-15166, and HST-GO-15312. The National Radio Astronomy Observatory is a facility of the NSF operated under cooperative agreement by Associated Universities, Inc. Research at Lick Observatory is partially supported by a generous gift from Google. A major upgrade of the Kast spectrograph on the Shane 3 m telescope at Lick Observatory was made possible through generous gifts from the Heising-Simons Foundation as well as William and Marina Kast. KAIT and its ongoing operation were made possible by donations from Sun Microsystems, Inc., the Hewlett-Packard Company, AutoScope Corporation, Lick Observatory, the NSF, the University of California, the Sylvia & Jim Katzman Foundation, and the TABASGO Foundation. The European VLBI Network is a joint facility of independent European, African, Asian, and North American radio astronomy institutes. Scientific results from data presented in this publication are derived from the following EVN project code(s): RR011. e-VLBI research infrastructure in Europe is supported by the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement No. RI-261525 NEXPReS. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona Board of Regents; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, The Leibniz Institute for Astrophysics Potsdam, and Heidelberg University; The Ohio State University, representing OSU, University of Notre Dame, University of Minnesota, and University of Virginia. This research uses data obtained through the Telescope Access Program (TAP). Observations obtained with the Hale telescope at Palomar Observatory were obtained as part of an agreement between the National Astronomical Observatories, Chinese Academy of Sciences, and the California Institute of Technology. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the observatory was made possible by the generous financial support of the W. M. Keck Foundation. We acknowledge the Keck Target of Opportunity Program for the spectrum obtained on 2017 October 22. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with NASA. Software: FAST (Kriek et al. 2009), IRAF (Tody 1986, 1993), LPipe (Perley 2019), HEAsoft (HEASARC 2014), MOSFiT (Guillochon et al. 2018).

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