Delayed Circumstellar Interaction for Type Ia SN 2015cp Revealed by an HST Ultraviolet Imaging Survey

M. L. Graham, C. E. Harris, P. E. Nugent, K. Maguire, M. Sullivan, M. Smith, S. Valenti, A. Goobar, O. D. Fox, K. J. Shen, P. L. Kelly, C. McCully, T. G. Brink, A. V. Filippenko

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17 Scopus citations


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 10 16 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.

Original languageEnglish (US)
Article number62
JournalAstrophysical Journal
Issue number1
StatePublished - Jan 20 2019

Bibliographical note

Funding Information:
This work is based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained (from the Data Archive) at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under National Aeronautics and Space Administration (NASA) contract NAS 5-26555. These observations are associated with program GO-14779 (PI Graham), for which support was provided by NASA through a grant from STScI, and with program GO-15407 (PI Graham).

Funding Information:
This work makes use of data from Las Cumbres Observatory, the Supernova Key Project, the BANZAI pipeline (McCully et al. 2018), and the Supernova Exchange, all of which are funded in part by National Science Foundation (NSF) grant AST-1313484. This work is based in part on observations from the Low Resolution Imaging Spectrometer at the Keck I telescope. We are grateful to the staff at Keck Observatory for their assistance. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; it 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. We thank Daniel Perley and Brad Cenko for the use of, and assistance with, their Keck LRIS imaging and spectroscopy reduction pipeline.24

Funding Information:
This paper uses data from SDSS-IV, published in the public domain. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. This paper made use of data from the Dark Energy Camera Legacy Survey (DECaLS), NOAO Proposal ID #2014B-0404 by PIs David Schlegel and Arjun Dey, from the Cerro Tololo Inter-American Observatory. NOAO is operated by AURA, Inc., under a cooperative agreement with the NSF.

Funding Information:
A.V.F.ʼs group at U.C. Berkeley has been supported by Gary & Cynthia Bengier, the Richard & Rhoda Goldman Fund, the Christopher R. Redlich Fund, the TABASGO Foundation, NSF grant AST–1211916, and the Miller Institute for Basic Research in Science. M.S. acknowledges support from EU/ FP7-ERC grant #615929. K.J.S. is supported by NASA through the Astrophysics Theory Program (NNX17AG28G). K.M. acknowledges support from the UK STFC through an Ernest Rutherford Fellowship and from the Horizon 2020 ERC Starting Grant (grant #758638).

Funding Information:
This work is based in part on observations made with the Kast Spectrograph on the Shane 3 m telescope at Lick Observatory. A major upgrade to the Kast spectrograph was recently made possible by a generous gift from the Heising-Simons Foundation as well as William and Marina Kast. Research at Lick Observatory is partially supported by a generous gift from Google. This work is based in part on observations made with ESO telescopes at the La Silla Paranal Observatory under programmes ID 099.D-0683(A) (PI Maguire) and ID 198.A-0915 (PI Sullivan). This work has made use of publicly available PanSTARRS data. Operation of the Pan-STARRS1 telescope is supported by NASA under grants NNX12AR65G and NNX14AM74G issued through the NEO Observation Program. This work is based (in part) on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile as part of PESSTO (the Public ESO Spectroscopic Survey for Transient Objects) ESO program 191.D-0935.

Publisher Copyright:
© 2019. The American Astronomical Society. All rights reserved.


  • supernovae: general
  • supernovae: individual (SN 2015cp, ASASSN-15og)


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