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 journalArticlepeer-review

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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
Pages (from-to)137-157
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Volume462
Issue number1
DOIs
StatePublished - 11 Oct 2016
Externally publishedYes

Funding

FundersFunder number
Gran Telescopio Canarias
Fundaciòn Galileo Galilei
NOT
Instituto de Astrofísica de Canarias
PESSTO
Generalitat de Catalunya
Spanish Ministerío Economía y Competitividad
Institute for Space Studies of Catalunya
Università degli Studi di Padova
Seventh Framework Programme291222
Liverpool John Moores University
European Research Council
Istituto Nazionale di Astrofisica
Science and Technology Facilities CouncilST/L000709/1, ST/M003035/1
Australian Research CouncilCE110001020
European Commission267251
Ministerio de Economía y CompetitividadESP2013-41268-R
National Science Foundation1313484

    Keywords

    • General
    • supernovae

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