K2 Observations of SN 2018oh Reveal a Two-component Rising Light Curve for a Type Ia Supernova

Journal Article · Fri Dec 28 00:00:00 EST 2018 · The Astrophysical Journal. Letters (Online)

DOI:https://doi.org/10.3847/2041-8213/aaedb0· OSTI ID:1526567

Dimitriadis, G.; Foley, R. J.; Rest, A.; Kasen, D.; Piro, A. L. ; Polin, A.; Jones, D. O. ; Villar, A. ; Narayan, G. ; A. Coulter, D. ; Kilpatrick, C. D. ; Pan, Y. -C.; Rojas-Bravo, C.; Fox, O. D. ; Jha, S. W. ; Nugent, P. E. ; Riess, A. G.; Scolnic, D.; Drout, M. R.; Barentsen, G. ; Dotson, J. ; Gully-Santiago, M. ; Hedges, C. ; Cody, A. M. ; Barclay, T. ; Howell, S. ; Garnavich, P. ; Tucker, B. E. ; Shaya, E. ; Mushotzky, R.; Olling, R. P.; Margheim, S. ; Zenteno, A.; Coughlin, J.; Cleve, J. E. Van; de Miranda Cardoso, J. Vinícius; Larson, K. A.; McCalmont-Everton, K. M.; Peterson, C. A.; Ross, S. E.; Reedy, L. H.; Osborne, D.; McGinn, C.; Kohnert, L.; Migliorini, L.; Wheaton, A.; Spencer, B.; Labonde, C.; Castillo, G.; Beerman, G.; Steward, K.; Hanley, M.; Larsen, R.; Gangopadhyay, R.; Kloetzel, R.; Weschler, T.; Nystrom, V.; Moffatt, J.; Redick, M.; Griest, K.; Packard, M.; Muszynski, M.; Kampmeier, J.; Bjella, R.; Flynn, S.; Elsaesser, B.; Chambers, K. C. ; Flewelling, H. A. ; Huber, M. E. ; Magnier, E. A.; Waters, C. Z.; Schultz, A. S. B.; Bulger, J.; Lowe, T. B.; Willman, M.; Smartt, S. J. ; Smith, K. W.; Points, S.; Strampelli, G. M.; Brimacombe, J.; Chen, P.; Muñoz, J. A. ; Mutel, R. L.; Shields, J. ; Vallely, P. J.; Villanueva, S.; Li, W.; Wang, X. ; Zhang, J. ; Lin, H.; Mo, J.; Zhao, X.; Sai, H.; Zhang, X.; Zhang, K.; Zhang, T.; Wang, L.; Zhang, J.; Baron, E. ; DerKacy, J. M.; Li, L.; Chen, Z.; Xiang, D.; Rui, L.; Wang, L.; Huang, F.; Li, X.; Hosseinzadeh, G. ; Howell, D. A.; Arcavi, I. ; Hiramatsu, D.; Burke, J.; Valenti, S. ; Tonry, J. L. ; Denneau, L.; Heinze, A. N. ; Weiland, H.; Stalder, B. ; Vinkó, J. ; Sárneczky, K. ; Pál, A. ; Bódi, A.; Bognár, Zs. ; Csák, B.; Cseh, B.; Csörnyei, G.; Hanyecz, O. ; Ignácz, B.; Kalup, Cs.; Könyves-Tóth, R.; Kriskovics, L.; Ordasi, A.; Rajmon, I.; Sódor, A.; Szabó, R. ; Szakáts, R. ; Zsidi, G.; Williams, S. C. ; Nordin, J.; Cartier, R.; Frohmaier, C. ; Galbany, L. ; Gutiérrez, C. P. ; Hook, I. ; Inserra, C. ; Smith, M. ; Sand, D. J. ; Andrews, J. E.; Smith, N.; Bilinski, C.

We present an exquisite 30 minute cadence Kepler (K2) light curve of the Type Ia supernova (SN Ia) 2018oh (ASASSN-18bt), starting weeks before explosion, covering the moment of explosion and the subsequent rise, and continuing past peak brightness. These data are supplemented by multi-color Panoramic Survey Telescope (Pan-STARRS1) and Rapid Response System 1 and Cerro Tololo Inter-American Observatory 4 m Dark Energy Camera (CTIO 4-m DECam) observations obtained within hours of explosion. The K2 light curve has an unusual two-component shape, where the flux rises with a steep linear gradient for the first few days, followed by a quadratic rise as seen for typical supernovae (SNe) Ia. This "flux excess" relative to canonical SN Ia behavior is confirmed in our i-band light curve, and furthermore, SN 2018oh is especially blue during the early epochs. The flux excess peaks 2.14 ± 0.04 days after explosion, has a FWHM of 3.12 ± 0.04 days, a blackbody temperature of $$T = 17,500^{+11,500}_{-9,000}$$ K, a peak luminosity of 4.3 ± 0.2 x 10³⁸ erg s^-1, and a total integrated energy of 1.27 ± 0.01 x 10⁴³ erg. We compare SN 2018oh to several models that may provide additional heating at early times, including collision with a companion and a shallow concentration of radioactive nickel. While all of these models generally reproduce the early K2 light curve shape, we slightly favor a companion interaction, at a distance of ~ 2 x 10¹² based on our early color measurements, although the exact distance depends on the uncertain viewing angle. Additional confirmation of a companion interaction in future modeling and observations of SN 2018oh would provide strong support for a single-degenerate progenitor system.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Contributing Organization: K2 Mission Team; KEGS; Kepler spacecraft team; Pan-STARRS; DECam; ASAS-SN; PTSS/TNTS; Las Cumbres Observatory; ATLAS; Konkoly; ePESSTO; University of Arizona
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1526567
• Journal Information: The Astrophysical Journal. Letters (Online), Vol. 870, Issue 1; ISSN 2041-8213
• Publisher: Institute of Physics (IOP)
• Country of Publication: United States
• Language: English

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79 ASTRONOMY AND ASTROPHYSICS