Despite their cosmological utility, the progenitors of Type Ia supernovae (SNe Ia) are still unknown, with many efforts focused on whether accretion from a nondegenerate companion can grow a carbon-oxygen white dwarf to near the Chandrasekhar mass. The association of SNe Ia resembling SN 1991T ("91T-like") with circumstellar interaction may be evidence for this "single-degenerate" channel. However, the observed circumstellar medium (CSM) in these interacting systems is unlike a stellar wind - of particular interest, it is sometimes detached from the stellar surface, residing at ∼1016 cm. A Hubble Space Telescope (HST) program to discover detached CSM around 91T-like SNe Ia successfully discovered interaction nearly two years after explosion in SN 2015cp (Graham et al. 2018). In this work, we present radio and X-ray follow-up observations of SN 2015cp and analyze them in the framework of Harris et al. (2016) to limit the properties of a constant-density CSM shell in this system. Assuming the HST detection took place shortly after the shock crossed the CSM, we constrain the total CSM mass in this system to be <0.5 . This limit is comparable to the CSM mass of supernova PTF11kx, but does not rule out lower masses predicted for recurrent novae. From lessons learned modeling PTF11kx and SN 2015cp, we suggest a strategy for future observations of these events to increase the sample of known interacting SNe Ia.
Bibliographical noteFunding Information:
A.H. acknowledges support from the I-Core Program of the Planning and Budgeting Committee and the Israel Science Foundation. This research was supported by a Grant from the GIF, the German-Israeli Foundation for Scientific Research and Development. Support for A.V.F.ʼs supernova research group has been provided by the TABASGO Foundation, Gary and Cynthia Bengier, the Christopher R. Redlich Fund, and the Miller Institute for Basic Research in Science (U.C. Berkeley). A.V.F.ʼs work was conducted in part at the Aspen Center for Physics, which is supported by NSF grant PHY-1607611; he thanks the Center for its hospitality during the supermassive black holes workshop in June and July 2018. K.M. acknowledges support from the UK STFC through an Ernest Rutherford Fellowship and from Horizon 2020 ERC Starting Grant (#758638). K.J.S. is supported by NASA through the Astrophysics Theory Program (NNX17AG28G).
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- binaries: symbiotic
- stars: mass-loss
- supernovae: general
- supernovae: individual (SN 2015cp)