Early ultraviolet emission in the Type Ia supernova LSQ12gdj: No evidence for ongoing shock interaction

R. A. Scalzo*, M. Childress, B. Tucker, F. Yuan, B. Schmidt, P. J. Brown, C. Contreras, N. Morrell, E. Hsiao, C. Burns, M. M. Phillips, A. Campillay, C. Gonzalez, K. Krisciunas, M. Stritzinger, M. L. Graham, J. Parrent, S. Valenti, C. Lidman, B. SchaeferN. Scott, M. Fraser, A. Gal-Yam, C. Inserra, K. Maguire, S. J. Smartt, J. Sollerman, M. Sullivan, F. Taddia, O. Yaron, D. R. Young, S. Taubenberger, C. Baltay, N. Ellman, U. Feindt, E. Hadjiyska, R. McKinnon, P. E. Nugent, D. Rabinowitz, E. S. Walker

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)
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We present photospheric-phase observations of LSQ12gdj, a slowly declining, UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has extinction-corrected absolute magnitude MB = -19.8, and pre-maximum spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN 2007if. We use ultraviolet photometry from Swift, ground-based optical photometry, and corrections from a near-infrared photometric template to construct the bolometric (1600-23 800 Å) light curve out to 45 d past B-band maximum light. We estimate that LSQ12gdj produced 0.96 ± 0.07 M· of 56Ni, with an ejected mass near or slightly above the Chandrasekhar mass. As much as 27 per cent of the flux at the earliest observed phases, and 17 per cent at maximum light, is emitted bluewards of 3300 Å. The absence of excess luminosity at late times, the cutoff of the spectral energy distribution bluewards of 3000 Å and the absence of narrow line emission and strong Na I D absorption all argue against a significant contribution from ongoing shock interaction. However, ~10 per cent of LSQ12gdj's luminosity near maximum light could be produced by the release of trapped radiation, including kinetic energy thermalized during a brief interaction with a compact, hydrogen-poor envelope (radius <1013 cm) shortly after explosion; such an envelope arises generically in double-degenerate merger scenarios.

Original languageEnglish
Pages (from-to)30-48
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Early online date22 Sep 2014
Publication statusPublished - 21 Nov 2014


  • Circumstellar matter-supernovae
  • General-supernovae
  • Individual
  • LSQ12gdj-white dwarfs
  • SN 2003fg
  • SN 2007if
  • SN 2009dc

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics


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