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

Scalzo, R. A., Childress, M., Tucker, B., Yuan, F., Schmidt, B., Brown, P. J., Contreras, C., Morrell, N., Hsiao, E., Burns, C., Phillips, M. M., Campillay, A., Gonzalez, C., Krisciunas, K., Stritzinger, M., Graham, M. L., Parrent, J., Valenti, S., Lidman, C., Schaefer, B., Scott, N., Fraser, M., Gal-Yam, A., Inserra, C., Maguire, K., Smartt, S. J., Sollerman, J., Sullivan, M., Taddia, F., Yaron, O., Young, D. R., Taubenberger, S., Baltay, C., Ellman, N., Feindt, U., Hadjiyska, E., McKinnon, R., Nugent, P. E., Rabinowitz, D. and Walker, E. S. 2014. Early ultraviolet emission in the Type Ia supernova LSQ12gdj: No evidence for ongoing shock interaction. Monthly Notices of the Royal Astronomical Society 445 (1) , pp. 30-48. 10.1093/mnras/stu1723

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Abstract

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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 24 January 2019
Date of Acceptance: 21 August 2014
Last Modified: 04 Feb 2019 12:01
URI: http://orca.cf.ac.uk/id/eprint/118791

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