The multifaceted Type II-L supernova 2014G from pre-maximum to nebular phase

G. Terreran*, A. Jerkstrand, S. Benetti, S. J. Smartt, P. Ochner, L. Tomasella, D. A. Howell, A. Morales-Garoffolo, A. Harutyunyan, E. Kankare, I. Arcavi, E. Cappellaro, N. Elias-Rosa, G. Hosseinzadeh, T. Kangas, A. Pastorello, L. Tartaglia, M. Turatto, S. Valenti, P. WigginsF. Yuan

*Corresponding author for this work

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

We present multiband ultraviolet, optical, and near-infrared photometry, along with visualwavelength spectroscopy, of supernova (SN) 2014G in the nearby galaxy NGC 3448 (25Mpc). The early-phase spectra show strong emission lines of the high ionization species He II/N IV/C IV during the first 2-3 d after explosion, traces of a metal-rich circumstellar material (CSM) probably due to pre-explosion mass-loss events. These disappear by day 9 and the spectral evolution then continues matching that of normal Type II SNe. The post-maximum light curve declines at a rate typical of Type II-L class. The extensive photometric coverage tracks the drop from the photospheric stage and constrains the radioactive tail, with a steeper decline rate than that expected from the 56Co decay if γ-rays are fully trapped by the ejecta. We report the appearance of an unusual feature on the blue side of H a after 100 d, which evolves to appear as a flat spectral feature linking H a and the [OI] doublet. This may be due to interaction of the ejecta with a strongly asymmetric, and possibly bipolar CSM. Finally, we report two deep spectra at ~190 and 340 d after explosion, the latter being arguably one of the latest spectra for a Type II-L SN. By modelling the spectral region around the [Ca II], we find a supersolar Ni/Fe production. The strength of the [O I] λλ6300,6363 doublet, compared with synthetic nebular spectra, suggests a progenitor with a zero-age main-sequence mass between 15 and 19 M.

Original languageEnglish
Article numberstw1591
Pages (from-to)137-157
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Volume462
Issue number1
Early online date04 Jul 2016
DOIs
Publication statusPublished - 11 Oct 2016

Keywords

  • General
  • supernovae

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Terreran, G., Jerkstrand, A., Benetti, S., Smartt, S. J., Ochner, P., Tomasella, L., Howell, D. A., Morales-Garoffolo, A., Harutyunyan, A., Kankare, E., Arcavi, I., Cappellaro, E., Elias-Rosa, N., Hosseinzadeh, G., Kangas, T., Pastorello, A., Tartaglia, L., Turatto, M., Valenti, S., ... Yuan, F. (2016). The multifaceted Type II-L supernova 2014G from pre-maximum to nebular phase. Monthly Notices of the Royal Astronomical Society, 462(1), 137-157. [stw1591]. https://doi.org/10.1093/mnras/stw1591