Astrophys. J., 866, 72-72 (2018/October-2)
IPTF 16hgs: a double-peaked Ca-rich gap transient in a metal-poor, star-forming dwarf galaxy.
DE K., KASLIWAL M.M., CANTWELL T., CAO Y., CENKO S.B., GAL-YAM A., JOHANSSON J., KONG A., KULKARNI S.R., LUNNAN R., MASCI F., MATUSZEWSKI M., MOOLEY K.P., NEILL J.D., NUGENT P.E., OFEK E.O., PERROTT Y., REBBAPRAGADA U.D., RUBIN A., O' SULLIVAN D. and YARON O.
Abstract (from CDS):
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 Reff) of a low-metallicity (≃0.4 Z☉), 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☉ 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☉ and radius of ≃13 R☉) in a core-collapse explosion of a highly stripped massive star in a close binary system.
© 2018. The American Astronomical Society. All rights reserved.
supernovae: general - supernovae: individual: iPTF 16hgs - surveys
Table 3: [DKC2018] ObjNN (Nos 1-12).
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