Discovery and Rapid Follow-up Observations of the Unusual Type II SN 2018ivc in NGC 1068

Creators: Bostroem, K. A.; Valenti, S.; Sand, D. J.; Andrews, J. E.; Van Dyk, S. D.; Galbany, L.; Pooley, D.; Amaro, R. C.; Smith, N.; Yang, S.; Anupama, G. C.; Arcavi, I.; Baron, E.; Brown, P. J.; Burke, J.; Cartier, R.; Hiramatsu, D.; Dong, Y.; Egami, E.; Ertel, S.; Filippenko, A. V.; Fox, O. D.; Haislip, J.; Hosseinzadeh, G.; Howell, D. A.; Gangopadhyay, A.; Jha, S. W.; Kouprianov, V.; Kumar, B.; Lundquist, M.; Milisavljevic, D.; McCully, C.; Milne, P.; Misra, K.; Reichart, D. E.; Sahu, D. K.; Sai, H.; Singh, A.; Smith, P. S.; Vinko, J.; Wang, X.; Wang, Y.; Wheeler, J. C.; Williams, G. G.; Wyatt, S.; Zhang, J.; Zhang, X.

Abstract

We present the discovery and high-cadence follow-up observations of SN 2018ivc, an unusual SNe II that exploded in NGC 1068 (D = 10.1 Mpc). The light curve of SN 2018ivc declines piecewise-linearly, changing slope frequently, with four clear slope changes in the first 30 days of evolution. This rapidly changing light curve indicates that interaction between the circumstellar material and ejecta plays a significant role in the evolution. Circumstellar interaction is further supported by a strong X-ray detection. The spectra are rapidly evolving and dominated by hydrogen, helium, and calcium emission lines. We identify a rare high-velocity emission-line feature blueshifted at ~7800 km s⁻¹ (in Hα, Hβ, Pβ, Pγ, He I, and Ca II), which is visible from day 18 until at least day 78 and could be evidence of an asymmetric progenitor or explosion. From the overall similarity between SN 2018ivc and SN 1996al, the Hα equivalent width of its parent H II region, and constraints from pre-explosion archival Hubble Space Telescope images, we find that the progenitor of SN 2018ivc could be as massive as 52 M⊙ but is more likely <12 M⊙. SN 2018ivc demonstrates the importance of the early discovery and rapid follow-up observations of nearby supernovae to study the physics and progenitors of these cosmic explosions.

Additional Information

© 2020 The American Astronomical Society. Received 2019 September 16; revised 2020 April 6; accepted 2020 April 7; published 2020 May 21. We are grateful to B. J. Fulton for providing us the image shown in Figure 1, to P. Chandra for analysis of the Swift XRT and GMRT data, and to Jared Goldberg, Charlie Kilpatrick, Morgan Fraser, and Stephen Smartt for insightful conversations. We are grateful to the referee for the insightful comments. Research by K.A.B., S.V., and Y.D. is supported by NSF grant AST–1813176. Research by D.J.S. is supported by NSF grants AST–1821967, 1821987, 1813708, 1813466, and 1908972. Research by J.E.A. and N.S. was supported by NSF grant AST–151559. L.G. was funded by the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 839090. J.B., D.H., C.M., and D.A.H. are supported by NSF grant AST–1313484. I.A. is a CIFAR Azrieli Global Scholar in the Gravity and the Extreme Universe Program and acknowledges support from that program, from the Israel Science Foundation (grant numbers 2108/18 and 2752/19), from the United States—Israel Binational Science Foundation (BSF), and from the Israeli Council for Higher Education Alon Fellowship. A.V.F. is grateful for financial assistance from the Christopher R. Redlich Fund, the TABASGO Foundation, and the Miller Institute for Basic Research in Science (UC Berkeley). The research of J.C.W. is supported by NSF grant AST–1813825. K.M. acknowledges the support from Department of Science and Technology (DST), Government of India and Indo-US Science and Technology Forum (IUSSTF) for the WISTEMM fellowship and the Department of Physics, UC Davis, where part of this work was carried out. P.J.B.'s work on SOUSA and core-collapse supernovae is supported by NASA ADAP grants NNX13AF35G and NNX17AF43G. D.P. gratefully acknowledges support provided by the National Aeronautics and Space Administration (NASA) through Chandra Award No. GO8-19051X issued by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. J.Z. is supported by the National Natural Science Foundation of China (NSFC, grants 11773067 and 11403096), the Youth Innovation Promotion Association of the CAS (grant 2018081), and the Western Light Youth Project. The work of X.W. is supported by the National Natural Science Foundation of China (NSFC grants 11325313 and 11633002) and the National Program on Key Research and Development Project (grant 2016YFA0400803). E.B. and J.D. are supported in part by NASA grant NNX16AB25G. This work was partially supported by the Open Project Program of the Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences. We thank the support staffs at the many observatories where data were obtained. Funding for the Li-Jiang 2.4 m telescope (LJT) has been provided by the Chinese Academy of Sciences and the People's Government of Yunnan Province. The LJT is jointly operated and administrated by Yunnan Observatories and Center for Astronomical Mega-Science, CAS. This work makes use of observations from the Las Cumbres Observatory network. Based in part on observations obtained at the Gemini Observatory under programs GS-2018B-Q-130 (PI: D. Sand). Gemini is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the NSF (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil). The data were processed using the Gemini IRAF package. We thank the queue service observers and technical support staff at Gemini Observatory for their assistance. This work is based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555. Support for program GO-15151 was provided by NASA through a grant from STScI. 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 university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University; and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Observations using Steward Observatory facilities were obtained as part of the large observing programme AZTEC: Arizona Transient Exploration and Characterization. Some observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. The LBT/MODS observations were obtained as part of a pilot effort at Steward Observatory to move to queue observing and include back-up programs for poor weather conditions or technical failures. We thank J. Power for coordinating the queue efforts for our LBT/MODS observations. Based in part on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, Inovações e Comunicações (MCTIC) do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU). The facilities at IAO and CREST are operated by the Indian Institute of Astrophysics, Bangalore. This research has made use of data obtained from the Chandra Data Archive and software provided by the Chandra X-ray Center (CXC) in the application packages CIAO and Sherpa. 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. Facilities: ARC (DIS) - , ARIES:ST - , ARIES:DFOT - , Beijing:2.16 m (BFOSC) - , CTIO:PROMPT - , Gemini:South (Flamingos-2) - , CXO - , HCT (HFOSC) - , HET (LRS2) - , HST (ACS - , WFPC2 - , WFC3) - , Keck: I (LRIS) - , Keck: II (DEIMOS) - , Las Cumbres Observatory (FLOYDS - , Sinistro) - , LBT (MODS) - , MAST - , MMT (Binospec) - , PO:1.2 m - , SALT (RSS) - , SOAR (Goodman) - , SO: Bok (SPOL) - , SO: Kuiper (Mont4K) SO:Super-LOTIS - , UMN:1.52 m - , Spitzer (IRAC - , MIPS) - , Swift (UVOT) - , YAO:2.4 m (YFOSC). - Software: astropy (Astropy Collaboratio et al. 2013; The Astropy Collaboration et al. 2018), lcogtsnpipe (Valenti et al. 2016), CIAO (Fruscione et al. 2006), Sherpa (Freeman et al. 2001), SpectRes (Carnall 2017).

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