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The very young type Ia supernova 2013dy: Discovery, and strong carbon absorption in early-time spectra

  • Author(s): Zheng, W
  • Silverman, JM
  • Filippenko, AV
  • Kasen, D
  • Nugent, PE
  • Graham, M
  • Wang, X
  • Valenti, S
  • Ciabattari, F
  • Kelly, PL
  • Fox, OD
  • Shivvers, I
  • Clubb, KI
  • Cenko, SB
  • Balam, D
  • Howell, DA
  • Hsiao, E
  • Li, W
  • Howie Marion, G
  • Sand, D
  • Vinko, J
  • Wheeler, JC
  • Zhang, J
  • et al.

The Type Ia supernova (SN Ia) 2013dy in NGC 7250 (d ≈ 13.7 Mpc) was discovered by the Lick Observatory Supernova Search. Combined with a prediscovery detection by the Italian Supernova Search Project, we are able to constrain the first-light time of SN 2013dy to be only 0.10 ± 0.05 days (2.4 ± 1.2 hr) before the first detection. This makes SN 2013dy the earliest known detection of an SN Ia. We infer an upper limit on the radius of the progenitor star of R 0 ≲ 0.25 R ⊙, consistent with that of a white dwarf. The light curve exhibits a broken power law with exponents of 0.88 and then 1.80. A spectrum taken 1.63 days after first light reveals a C II absorption line comparable in strength to Si II. This is the strongest C II feature ever detected in a normal SN Ia, suggesting that the progenitor star had significant unburned material. The C II line in SN 2013dy weakens rapidly and is undetected in a spectrum 7 days later, indicating that C II is detectable for only a very short time in some SNe Ia. SN 2013dy reached a B-band maximum of MB = -18.72 ± 0.03 mag ∼17.7 days after first light. © 2013. The American Astronomical Society. All rights reserved.

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