SPIRITS 15c and SPIRITS 14buu: Two Obscured Supernovae in the Nearby Star-forming Galaxy IC 2163

Jacob E. Jencson, Mansi M. Kasliwal, Joel Johansson, Carlos Contreras, Sergio Castellón, Howard E. Bond, Andrew J. Monson, Frank J. Masci, Ann Marie Cody, Jennifer E. Andrews, John Bally, Yi Cao, Ori D. Fox, Timothy Gburek, Robert D. Gehrz, Wayne Green, George Helou, Eric Hsiao, Nidia Morrell, Mark PhillipsThomas A. Prince, Robert A. Simcoe, Nathan Smith, Samaporn Tinyanont, Robert Williams

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10 Scopus citations


SPitzer InfraRed Intensive Transients Survey - SPIRITS - is an ongoing survey of nearby galaxies searching for infrared (IR) transients with Spitzer/IRAC. We present the discovery and follow-up observations of one of our most luminous (M [4.5] = -17.1 ± 0.4 mag, Vega) and reddest ([3.6] - [4.5] = 3.0 ± 0.2 mag) transients, SPIRITS 15c. The transient was detected in a dusty spiral arm of IC 2163 (D ≈ 35.5 Mpc). Pre-discovery ground-based imaging revealed an associated, shorter-duration transient in the optical and near-IR (NIR). NIR spectroscopy showed a broad (≈8400 km s-1), double-peaked emission line of He i at 1.083 μm, indicating an explosive origin. The NIR spectrum of SPIRITS 15c is similar to that of the Type IIb SN 2011dh at a phase of ≈200 days. Assuming an A V = 2.2 mag of extinction in SPIRITS 15c provides a good match between their optical light curves. The NIR light curves, however, show some minor discrepancies when compared with SN 2011dh, and the extreme [3.6]-[4.5] color has not been previously observed for any SN IIb. Another luminous (M 4.5 = -16.1 ± 0.4 mag) event, SPIRITS 14buu, was serendipitously discovered in the same galaxy. The source displays an optical plateau lasting ≳80 days, and we suggest a scenario similar to the low-luminosity Type IIP SN 2005cs obscured by A V ≈ 1.5 mag. Other classes of IR-luminous transients can likely be ruled out in both cases. If both events are indeed SNe, this may suggest that ≳18% of nearby core-collapse SNe are missed by currently operating optical surveys.

Original languageEnglish (US)
Article number167
JournalAstrophysical Journal
Issue number2
StatePublished - Mar 10 2017

Bibliographical note

Funding Information:
Supported by the National Science Foundation Graduate Research Fellowship under grant no. DGE-1144469. H.E.B. acknowledges support for this work provided by NASA through grants GO-13935 and GO-14258 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. R.D.G. was supported in part by the United States Air Force.

Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved..


  • supernovae: general
  • supernovae: individual (SPIRITS 15c, SPIRITS 14buu)
  • surveys


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