Delayed Circumstellar Interaction for Type Ia SN 2015cp Revealed by an HST Ultraviolet Imaging Survey
Abstract
The nature and role of the binary companion of carbon-oxygen white dwarf stars that explode as Type Ia supernovae (SNe Ia) are not yet fully understood. Past detections of circumstellar material (CSM) that contain hydrogen for a small number of SN Ia progenitor systems suggest that at least some have a nondegenerate companion. In order to constrain the prevalence, location, and quantity of CSM in SN Ia systems, we performed a near-ultraviolet (NUV) survey with the Hubble Space Telescope (HST) to look for the high-energy signature of SN Ia ejecta interacting with the CSM. Our survey revealed that SN 2015cp, an SN 1991T-like overluminous SN Ia, was experiencing late-onset interaction between its ejecta and the surrounding CSM 664 days after its light-curve peak. We present ground- and space-based follow-up observations of SN 2015cp that reveal optical emission lines of H and Ca, typical signatures of ejecta-CSM interaction. We show how SN 2015cp was likely similar to the well-studied SN Ia-CSM event PTF11kx, making it the second case in which an unambiguously classified SN Ia was observed to interact with a distant shell of CSM that contains hydrogen (R CSM ≳ 1016 cm). The remainder of our HST NUV images of SNe Ia were nondetections that we use to constrain the occurrence rate of observable late-onset CSM interaction. We apply theoretical models for the emission from ejecta-CSM interaction to our NUV nondetections and place upper limits on the mass and radial extent of CSM in SN Ia progenitor systems.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2019
- DOI:
- 10.3847/1538-4357/aaf41e
- arXiv:
- arXiv:1812.02757
- Bibcode:
- 2019ApJ...871...62G
- Keywords:
-
- supernovae: general;
- supernovae: individual: SN 2015cp;
- ASASSN-15og;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 29 pages, 10 figures, 6 tables