A1 Refereed original research article in a scientific journal
The multifaceted Type II-L supernova 2014G from pre-maximum to nebular phase
Authors: Terreran G, Jerkstrand A, Benetti S, Smartt SJ, Ochner P, Tomasella L, Howell DA, 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, Wiggins P, Yuan F
Publisher: OXFORD UNIV PRESS
Publication year: 2016
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 462
Issue: 1
First page : 137
Last page: 157
Number of pages: 21
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stw1591
Abstract
We present multiband ultraviolet, optical, and near-infrared photometry, along with visual-wavelength 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 Co-56 decay if gamma-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 alpha 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 similar to 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] lambda lambda 6300,6363 doublet, compared with synthetic nebular spectra, suggests a progenitor with a zero-age main-sequence mass between 15 and 19 M-circle dot.
We present multiband ultraviolet, optical, and near-infrared photometry, along with visual-wavelength 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 Co-56 decay if gamma-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 alpha 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 similar to 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] lambda lambda 6300,6363 doublet, compared with synthetic nebular spectra, suggests a progenitor with a zero-age main-sequence mass between 15 and 19 M-circle dot.
UTU Research Portal