TY - JOUR
T1 - iPTF 16hgs
T2 - A Double-peaked Ca-rich Gap Transient in a Metal-poor, Star-forming Dwarf Galaxy
AU - De, Kishalay
AU - Kasliwal, Mansi M.
AU - Cantwell, Therese
AU - Cao, Yi
AU - Cenko, S. Bradley
AU - Gal-Yam, Avishay
AU - Johansson, Joel
AU - Kong, Albert
AU - Kulkarni, Shrinivas R.
AU - Lunnan, Ragnhild
AU - Masci, Frank
AU - Matuszewski, Matt
AU - Mooley, Kunal P.
AU - Neill, James D.
AU - Nugent, Peter E.
AU - Ofek, Eran O.
AU - Perrott, Yvette
AU - Rebbapragada, Umaa D.
AU - Rubin, Adam
AU - O' Sullivan, Donal
AU - Yaron, Ofer
N1 - 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 the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. These results made use of the Discovery Channel Telescope at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy and operates the DCT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University, and Yale University. The upgrade of the DeVeny optical spectrograph has been funded by a generous grant from John and Ginger Giovale. We thank the staff of the Mullard Radio Astronomy Observatory for their invaluable assistance in the commissioning and operation of AMI, which is supported by Cambridge University and the European Research Council under grant ERC-2012-StG-307215 LODESTONE. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We thank the staff of the GMRT that made these observations possible. The GMRT is run by the National Center for Radio Astrophysics of the Tata Institute of Fundamental Research. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Y.C.P. is supported by a Trinity College JRF.
PY - 2018/10/10
Y1 - 2018/10/10
N2 - Calcium-rich gap transients represent an intriguing new class of faint and fast-evolving supernovae that exhibit strong [Ca ii] emission in their nebular phase spectra. In this paper, we present the discovery and follow-up observations of a faint and fast-evolving transient, iPTF 16hgs, that exhibited a double-peaked light curve. Exhibiting a Type Ib spectrum in the photospheric phase and an early transition to a [Ca ii] dominated nebular phase, iPTF 16hgs shows properties consistent with the class of Ca-rich gap transients, with two important exceptions. First, while the second peak of the light curve is similar to other Ca-rich gap transients, the first blue and fast-fading peak (declining over ≈2 days) is unique to this source. Second, we find that iPTF 16hgs occurred in the outskirts (projected offset of ≈6 kpc ≈ 1.9 R eff) of a low-metallicity (≈0.4 Z o), star-forming, dwarf spiral galaxy. Deep limits from late-time radio observations suggest a low-density environment for the source. If iPTF 16hgs shares explosion physics with the class of Ca-rich gap transients, the first peak can be explained by the presence of 0.01 M o of 56Ni in the outer layers the ejecta, reminiscent of some models of He-shell detonations on WDs. However, if iPTF 16hgs is physically unrelated to the class, the first peak is consistent with shock cooling emission (of an envelope with a mass of ≈0.08 M o and radius of ≈13 R o) in a core-collapse explosion of a highly stripped massive star in a close binary system.
AB - Calcium-rich gap transients represent an intriguing new class of faint and fast-evolving supernovae that exhibit strong [Ca ii] emission in their nebular phase spectra. In this paper, we present the discovery and follow-up observations of a faint and fast-evolving transient, iPTF 16hgs, that exhibited a double-peaked light curve. Exhibiting a Type Ib spectrum in the photospheric phase and an early transition to a [Ca ii] dominated nebular phase, iPTF 16hgs shows properties consistent with the class of Ca-rich gap transients, with two important exceptions. First, while the second peak of the light curve is similar to other Ca-rich gap transients, the first blue and fast-fading peak (declining over ≈2 days) is unique to this source. Second, we find that iPTF 16hgs occurred in the outskirts (projected offset of ≈6 kpc ≈ 1.9 R eff) of a low-metallicity (≈0.4 Z o), star-forming, dwarf spiral galaxy. Deep limits from late-time radio observations suggest a low-density environment for the source. If iPTF 16hgs shares explosion physics with the class of Ca-rich gap transients, the first peak can be explained by the presence of 0.01 M o of 56Ni in the outer layers the ejecta, reminiscent of some models of He-shell detonations on WDs. However, if iPTF 16hgs is physically unrelated to the class, the first peak is consistent with shock cooling emission (of an envelope with a mass of ≈0.08 M o and radius of ≈13 R o) in a core-collapse explosion of a highly stripped massive star in a close binary system.
UR - http://www.scopus.com/inward/record.url?scp=85055161724&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/aadf8e
DO - 10.3847/1538-4357/aadf8e
M3 - مقالة
SN - 0004-637X
VL - 866
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 72
ER -