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

  • Author(s): Dimitriadis, G
  • Foley, RJ
  • Rest, A
  • Kasen, D
  • Piro, AL
  • Polin, A
  • Jones, DO
  • Villar, A
  • Narayan, G
  • A. Coulter, D
  • Kilpatrick, CD
  • Pan, Y-C
  • Rojas-Bravo, C
  • Fox, OD
  • Jha, SW
  • Nugent, PE
  • Riess, AG
  • Scolnic, D
  • Drout, MR
  • Barentsen, G
  • Dotson, J
  • Gully-Santiago, M
  • Hedges, C
  • Cody, AM
  • Barclay, T
  • Howell, S
  • Garnavich, P
  • Tucker, BE
  • Shaya, E
  • Mushotzky, R
  • Olling, RP
  • Margheim, S
  • Zenteno, A
  • Coughlin, J
  • Cleve, JE Van
  • de Miranda Cardoso, J Vinícius
  • Larson, KA
  • McCalmont-Everton, KM
  • Peterson, CA
  • Ross, SE
  • Reedy, LH
  • 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, KC
  • Flewelling, HA
  • Huber, ME
  • Magnier, EA
  • Waters, CZ
  • Schultz, ASB
  • Bulger, J
  • Lowe, TB
  • Willman, M
  • Smartt, SJ
  • Smith, KW
  • Points, S
  • Strampelli, GM
  • Brimacombe, J
  • Chen, P
  • Muñoz, JA
  • Mutel, RL
  • Shields, J
  • Vallely, PJ
  • 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, JM
  • Li, L
  • Chen, Z
  • Xiang, D
  • Rui, L
  • Wang, L
  • Huang, F
  • Li, X
  • Hosseinzadeh, G
  • Howell, DA
  • Arcavi, I
  • Hiramatsu, D
  • Burke, J
  • Valenti, S
  • Tonry, JL
  • Denneau, L
  • Heinze, AN
  • 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, SC
  • Nordin, J
  • Cartier, R
  • Frohmaier, C
  • Galbany, L
  • Gutiérrez, CP
  • Hook, I
  • Inserra, C
  • Smith, M
  • Sand, DJ
  • Andrews, JE
  • Smith, N
  • Bilinski, C
  • et al.
Abstract

© 2018. The American Astronomical Society. All rights reserved.. 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 K, a peak luminosity of , and a total integrated energy of . 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 ∼ 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.

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