On the Origin of SN 2016hil—A Type II Supernova in the Remote Outskirts of an Elliptical Host

Journal Article · 15 December 2019 · The Astrophysical Journal (Online)

DOI: https://doi.org/10.3847/1538-4357/ab505d · OSTI ID:1580977

Irani, Ido  ^[1]; Schulze, Steve  ^[1]; Gal-Yam, Avishay  ^[1]; Lunnan, Ragnhild  ^[2]; Brink, Thomas G. ^[3]; Zheng, WeiKang  ^[3]; Filippenko, Alexei V.  ^[4]; Yang, Yi ^[2]; de Jaeger, Thomas  ^[3]; Nugent, Peter E.  ^[5]; Kasliwal, Mansi M.  ^[6]; Fremling, Christoffer  ^[6]; Neill, James Don ^[6]; Rebbapragada, Umaa  ^[7]; Masci, Frank J.  ^[8]; Sollerman, Jesper  ^[2]; Yaron, Ofer ^[1]

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1. Weizmann Inst. of Science, Rehovot (Israel)
2. Stockholm Univ. (Sweden). Oskar Klein Centre
3. Univ. of California, Berkeley, CA (United States)
4. Univ. of California, Berkeley, CA (United States). Miller Inst. for Basic Research in Science
5. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
6. California Inst. of Technology (CalTech), Pasadena, CA (United States)
7. California Inst. of Technology (CalTech), Pasadena, CA (United States). Jet Propulsion Lab. (JPL)
8. California Inst. of Technology (CalTech), Pasadena, CA (United States). Infrared Processing and Analysis Center (IPAC)

Type II supernovae (SNe) stem from the core collapse of massive ($$>8\ M_{\odot}$$) stars. Owing to their short lifespan, we expect a very low rate of such events in elliptical host galaxies, where the star-formation rate is low, and which mostly consist of an old stellar population. SN 2016hil (iPTF16hil) is a Type II supernova located in the extreme outskirts of an elliptical galaxy at redshift $z=0.0608$ (projected distance $27.2$ kpc). It was detected near peak brightness ($$M_{r} \approx -17$$ mag) 9 days after the last nondetection. SN 2016hil has some potentially peculiar properties: while presenting a characteristic spectrum, the event was unusually short lived and declined by $$\sim 1.5$$ mag in $< 40$ days, following an apparently double-peaked light curve. Its spectra suggest a low metallicity ($$Z<0.4\ Z_{\odot}$$). We place a tentative upper limit on the mass of a potential faint host at $$\log(M/M_{\odot}) =7.27^{+0.43}_{-0.24}$$ using deep Keck optical imaging. In light of this, we discuss the possibility of the progenitor forming locally, and other more exotic formation scenarios such as a merger or common-envelope evolution causing a time-delayed explosion. Further observations of the explosion site in the ultraviolet are needed in order to distinguish between the cases. Regardless of the origin of the transient, observing a population of such seemingly hostless Type II SNe could have many uses, including an estimate the number of faint galaxies in a given volume, and tests of the prediction of a time-delayed population of core-collapse SNe in locations otherwise unfavorable for the detection of such events.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC); European Union (EU); National Aeronautics and Space Administration (NASA); National Science Foundation (NSF)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1580977
• Journal Information: The Astrophysical Journal (Online), Journal Name: The Astrophysical Journal (Online) Journal Issue: 2 Vol. 887; ISSN 1538-4357
• Publisher: Institute of Physics (IOP)Copyright Statement
• Country of Publication: United States
• Language: English