http://arxiv.org/abs/1612.07321
Super-luminous supernovae (SLSNe) are tremendously luminous explosions whose power sources and progenitors are highly debated. Broad-lined SNe Ic (SNe Ic-bl) are the only type of SNe that are connected with long duration gamma ray bursts (GRBs). Studying the spectral similarity and difference between the populations of hydrogen-poor SLSNe (SLSNe I) and of hydrogen-poor stripped-envelope core-collapse SNe, in particular SNe Ic and SNe Ic-bl, can provide crucial observations to test predictions of theories based on various power source models and progenitor models. In this paper, we collected all of the published optical spectra of 32 SLSNe I, 21 SNe Ic-bl, as well as 17 SNe Ic, quantified their spectral features, constructed average spectra, and compared them in a systematic way using new tools we have developed recently. We find that SLSNe I and SNe Ic-bl have comparable average spectral features and average absorption velocities at all phases, which are $\sim1$0,000 \kms~broader and $\sim8$,000 \kms~higher than those in SNe Ic at specifically 15 days after the date of maximum light, respectively. We find that the presence of a narrow `w’ feature around 4300 \AA, in addition to a blue continuum, at early phases is likely to be an indicator for SLSNe I spectra, as suggested in earlier works. Moreover, we find that such high absorption and width velocities may be hard to explain by the interaction model, and none of 13 SLSNe I with measured absorption velocities spanning over 10 days has a convincing flat velocity-evolution, which is inconsistent with the magnetar model in one dimension. Lastly, we find that SN 2011kl, the first SN that is connected with an ultra-long GRB, is broadly consistent with the mean spectrum of SLSNe I, but does not resemble the SNe Ic-bl that have accompanied long-duration GRBs when considering the spectral continuum.
Y. Liu and M. Modjaz
Fri, 23 Dec 16
33/60
Comments: Submitted to ApJ. 13 pages, 7 figures, 3 tables. Comments welcome
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