After the Fall: Late-Time Spectroscopy of Type IIP Supernovae

Abstract

Herein we analyse late-time (post-plateau; 103 < t < 1229 d) optical spectra of low-redshift (z < 0.016), hydrogen-rich Type IIP supernovae (SNe IIP). Our newly constructed sample contains 91 nebular spectra of 38 SNe IIP, which is the largest dataset of its kind ever analysed in one study, and many of the objects have complementary photometric data. We determined the peak and total luminosity, velocity of the peak, HWHM intensity, and profile shape for many emission lines. Temporal evolution of these values and various flux ratios are studied. We also investigate the correlations between these measurements and photometric observables, such as the peak and plateau absolute magnitudes and the late-time light curve decline rates in various optical bands. The strongest and most robust result we find is that the luminosities of all spectral features (except those of helium) tend to be higher in objects with steeper late-time V-band decline rates. A steep late-time V-band slope likely arises from less efficient trapping of gamma-rays and positrons, which could be caused by multidimensional effects such as clumping of the ejecta or asphericity of the explosion itself. Furthermore, if gamma-rays and positrons can escape more easily, then so can photons via the observed emission lines, leading to more luminous spectral features. It is also shown that SNe IIP with larger progenitor stars have ejecta with a more physically extended oxygen layer that is well-mixed with the hydrogen layer. In addition, we find a subset of objects with evidence for asymmetric Ni-56 ejection, likely bipolar in shape. We also compare our observations to theoretical late-time spectral models of SNe IIP from two separate groups and find moderate-to-good agreement with both sets of models. Our SNe IIP spectra are consistent with models of 12-15 M_Sun progenitor stars having relatively low metallicity (Z $\le$ 0.01).

resubmitted to MNRAS, 50 pages (29 of which are tables), 15 figures, 10 tables

References in corpus (15)

• Characterizing the V-band light-curves of hydrogen-rich type II supernovae
• SN 2005cs in M51 II. Complete Evolution in the Optical and the Near-Infrared
• Towards Characterization of the Type IIP Supernova Progenitor Population: a Statistical Sample of Light Curves from Pan-STARRS1
• Dust and the type II-plateau supernova 2004et
• A non-spherical core in the explosion of supernova SN 2004dj
• Photometric and Spectroscopic Properties of Type II-P Supernovae
• The Standardized Candle Method for Type II Plateau Supernovae
• A Sample of Type II-L Supernovae
• Optical and infrared observations of the Type IIP SN2002hh from day 3 to 397
• Analysis of blue-shifted emission peaks in type II supernovae
• Supersolar Ni/Fe production in the Type IIP SN 2012ec
• The first year of SN 2004dj in NGC 2403
• SN 2013ab : A normal type IIP supernova in NGC 5669
• SN 2012ec: mass of the progenitor from PESSTO follow-up of the photospheric phase
• An Extremely Bright Echo Associated With SN 2002hh

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