42 research outputs found
Type II-Plateau supernova radiation: dependencies on progenitor and explosion properties
We explore the properties of Type II-Plateau (II-P) supernovae (SNe) together
with their red-supergiant (RSG) star progenitors. Using MESA STAR, we modulate
the parameters (e.g., mixing length, overshoot, rotation, metallicity) that
control the evolution of a 15Msun main-sequence star to produce a variety of
physical pre-SN models and SN II-P ejecta. We extend previous modeling of SN
II-P radiation to include photospheric and nebular phases, as well as
multi-band light curves and spectra. Our treatment does not assume local
thermodynamic equilibrium, is time dependent, treats explicitly the effects of
line blanketing, and incorporates non-thermal processes. We find that the color
properties of SNe II-P require large model atoms for FeI and FeII, much larger
than adopted in Dessart & Hillier (2011). The color properties also imply RSG
progenitors of limited extent (~500Rsun) --- larger progenitor stars produce a
SN II-P radiation that remains too blue for too long. This finding calls for a
reduction of RSG radii, perhaps through a strengthening of convective energy
transport in RSG envelopes. Increased overshoot and rotation reduce the ratio
of ejecta to helium-core mass, similarly to an increase in main-sequence mass,
and thus complicate the inference ofprogenitor masses. In contrast to the great
sensitivity on progenitor radius, SN II-P color evolution appears insensitive
to variations in explosion energy. Finally, we document the numerous SN II-P
signatures that vary with progenitor metallicity, revealing their potential for
metallicity determinations in the nearby and distant Universe.Comment: Paper accepted to MNRA
Radiative Properties of Pair-instability Supernova Explosions
We present non-LTE time-dependent radiative-transfer simulations of
pair-instability supernovae (PISNe) stemming from red-supergiant (RSG),
blue-supergiant (BSG) and Wolf-Rayet (WR) star rotation-free progenitors born
in the mass range 160-230Msun, at 10^-4 Zsun. Although subject to uncertainties
in convection and stellar mass-loss rates, our initial conditions come from
physically-consistent models that treat evolution from the main-sequence, the
onset of the pair-production instability, and the explosion phase. With our set
of input models characterized by large 56Ni and ejecta masses, and large
kinetic energies, we recover qualitatively the Type II-Plateau, II-peculiar,
and Ib/c light-curve morphologies, although they have larger peak bolometric
luminosities (~10^9 to 10^10 Lsun) and a longer duration (~200d). We discuss
the spectral properties for each model during the photospheric and nebular
phases, including Balmer lines in II-P and II-pec at early times, the dominance
of lines from intermediate-mass-elements (IMEs) near the bolometric maximum,
and the strengthening of metal line blanketing thereafter. Having similar
He-core properties, all models exhibit similar post-peak spectra that are
strongly blanketed by FeII and FeI lines, characterized by red colors, and that
arise from photospheres/ejecta with a temperature of <4000K. Combined with the
modest line widths after bolometric peak, these properties contrast with those
of known super-luminous SNe suggesting that PISNe are yet to be discovered.
Being reddish, PISNe will be difficult to observe at high redshift except when
they stem from RSG explosions, in which case they could be used as metallicity
probes and distance indicators.Comment: accepted to MNRA