OPTICAL AND ULTRAVIOLET OBSERVATIONS OF A LOW-VELOCITY TYPE II PLATEAU SUPERNOVA 2013am IN M65

Abstract

Optical and ultraviolet observations for the nearby type II-plateau supernova (SN IIP) 2013am in the nearby spiral galaxy M65 are presented in this paper. The early spectra are characterized by relatively narrow P-Cygni features, with ejecta velocities much lower than observed in normal SNe IIP (i.e., ∼2000 km s −1 vs. ∼5000 km −1 in the middle of the plateau phase). Moreover, prominent Ca II absorptions are also detected in SN 2013am at relatively early phases. These spectral features are reminiscent of those seen in the low-velocity and low-luminosity SN IIP 2005cs. However, SN 2013am exhibits different photometric properties, having shorter plateau phases and brighter lightcurve tails if compared to SN 2005cs. Adopting R V =3.1 and a mean value of total reddening derived from the photometric and spectroscopic methods(i.e., E(B − V ) = 0.55±0.19 mag), we find that SN 2013am may have reached an absolute V -band peak magnitude of −15.83 ± 0.71 mag, and produced a 56 Ni mass of 0.016 +0.010 −0.006 M in the explosion. These parameters are close to those derived for SN 2008in and SN 2009N which have been regarded as "gap-filler" objects linking the faint SNe IIP to the normal ones. This indicates that some low-velocity SNe IIP may not necessarily result from the low-energetic explosions, and the low expansion velocities could be due to a lower metallicity of the progenitor stars, a larger envelope mass ejected in the explosion, or that is was observed at an angle that is away from the polar direction. Subject headings: supernovae:general -supernovae: Individual (SN 2013am) 1 Yunnan Observatories (YNAO), Chinese Academy of Sciences,

Type Ii Supernova Energetics and Comparison of Light Curves to Shock-Cooling Models

“…Bose et al (2015) estimated E/M from hydrodynamic modeling, making it difficult to assess the source of this discrepancy. Note that our derived 56 Ni mass of 5 10 3´-M  for iPTF13aaz (SN 2013am) is lower than the 1.5 10 2 -M  reported by Zhang et al (2014), but the source of this discrepancy is unclear. We find that the 56 Ni mass is strongly correlated with E/M ( 0.76 r = , P-value 0.05;  Figure 9).…”

“…Photometry for PTF12cod was supplemented with data from the 40-inch telescope at the Mount Laguna Observatory (MLO), which was also obtained with PSF fitting; see Smith et al (2015) for details on the MLO reduction procedure. Photometry for PTF10vdl (SN 2010id) was supplemented with that published by Gal-Yam et al (2011), photometry for PTF12bvh (SN 2012aw) was supplemented with that published by Munari et al (2013), and photometry for PTF13aaz (SN 2013am) was supplemented with that published by Zhang et al (2014).…”

SNe 2013K and 2013am: observed and physical properties of two slow, normal Type IIP events

“…Over the course of the photometric followup campaign, it became apparent that the luminosity and duration of the plateau-phase for SNe 2013K and 2013am are closers to those of the intermediate-luminosity Type IIP SNe, matching SN 2012A ) rather than more extreme sub-luminous Type IIP SNe. We note that optical data for SN 2013am (complemented by public Swift U V photometry) have been previously reported by Zhang et al (2014).…”

SN 2015ba: a Type IIP supernova with a long plateau

“…The explosion energy, ejecta mass and 56 Ni mass of SN 2009js is found to be similar to sub-luminous SNe, while exhibiting a significantly higher luminosity, comparable to those of intermediate luminosity events (Gandhi et al 2013). The early spectra of SN 2013am featured relatively narrow P-Cygni profiles and prominent Ca II and Ba II lines, similar to the low luminosity and low velocity SN 2005cs, while with a shorter plateau phase and brighter light curve tail, the photometric properties of this event deviated from those of SN 2005cs (Zhang et al 2014;Tomasella et al 2018). These controversial properties of SNe IIP motivated the study of each of them in greater detail.…”