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Register a new userThe Initial Masses of the Red Supergiant Progenitors to Type-II Supernovae
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There are a growing number of nearby SNe for which the progenitor star is detected in archival pre-explosion imaging. From these images it is possible to measure the progenitors brightness a few years before explosion, and ultimately estimate its initial mass. Previous work has shown that II-P and II-L supernovae (SNe) have Red Supergiant (RSG) progenitors, and that the range of initial masses for these progenitors seems to be limited to $<$17M$_odot$. This is in contrast with the cutoff of 25-30M$_odot$ predicted by evolutionary models, a result which is termed the Red Supergiant Problem. Here we investigate one particular source of systematic error present in converting pre-explosion photometry into an initial mass, that of the bolometric correction (BC) used to convert a single-band flux into a bolometric luminosity. We show, using star clusters, that RSGs evolve to later spectral types as they approach SN, which in turn causes the BC to become larger. Failure to account for this results in a systematic underestimate of a stars luminosity, and hence its initial mass. Using our empirically motivated BCs we reappraise the II-P and II-L SNe that have their progenitors detected in pre-explosion imaging. Fitting an initial mass function to these updated masses results in an increased upper mass cutoff of $M_{rm hi}$=$19.0^{+2.5}_{-1.3}$M$_odot$, with a 95% upper confidence limit of $<$27M$_odot$. Accounting for finite sample size effects and systematic uncertainties in the mass-luminosity relationship raises the cutoff to $M_{rm hi}$=25M$_odot$ ($<$33M$_odot$, 95% confidence). We therefore conclude that there is currently no strong evidence for `missing high mass progenitors to core-collapse SNe.
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By comparing the properties of Red Supergiant (RSG) supernova progenitors to those of field RSGs, it has been claimed that there is an absence of progenitors with luminosities $L$ above $log(L/L_odot) > 5.2$. This is in tension with the empirical upper luminosity limit of RSGs at $log(L/L_odot) = 5.5$, a result known as the `Red Supergiant Problem. This has been interpreted as evidence for an upper mass threshold for the formation of black-holes. In this paper, we compare the observed luminosities of RSG SN progenitors with the observed RSG $L$-distribution in the Magellanic Clouds. Our results indicate that the absence of bright SN II-P/L progenitors in the current sample can be explained at least in part by the steepness of the $L$-distribution and a small sample size, and that the statistical significance of the Red Supergiant Problem is between 1-2$sigma$ . Secondly, we model the luminosity distribution of II-P/L progenitors as a simple power-law with an upper and lower cutoff, and find an upper luminosity limit of $log(L_{rm hi}/L_odot) = 5.20^{+0.17}_{-0.11}$ (68% confidence), though this increases to $sim$5.3 if one fixes the power-law slope to be that expected from theoretical arguments. Again, the results point to the significance of the RSG Problem being within $sim 2 sigma$. Under the assumption that all progenitors are the result of single-star evolution, this corresponds to an upper mass limit for the parent distribution of $M_{rm hi} = 19.2{rm M_odot}$, $pm1.3 {rm M_odot (systematic)}$, $^{+4.5}_{-2.3} {rm M_odot}$ (random) (68% confidence limits).
Context. The companions of the exploding carbon-oxygen white dwarfs (CO WDs) for producing type Ia supernovae (SNe Ia) are still not conclusively confirmed. A red-giant (RG) star has been suggested to be the mass donor of the exploding WD, named as the symbiotic channel. However, previous studies on the this channel gave a relatively low rate of SNe Ia. Aims. We aim to systematically investigate the parameter space, Galactic rates and delay time distributions of SNe Ia from the symbiotic channel by employing a revised mass-transfer prescription. Methods. We adopted an integrated mass-transfer prescription to calculate the mass-transfer process from a RG star onto the WD. In this prescription, the mass-transfer rate varies with the local material states. Results. We evolved a large number of WD+RG systems, and found that the parameter space of WD+RG systems for producing SNe Ia is significantly enlarged. This channel could produce SNe Ia with intermediate and old ages, contributing to at most 5% of all SNe Ia in the Galaxy. Our model increases the SN Ia rate from this channel by a factor of 5. We suggest that the symbiotic systems RS Oph and T CrB are strong candidates for the progenitors of SNe Ia.
We review all the models proposed for the progenitor systems of Type Ia supernovae and discuss the strengths and weaknesses of each scenario when confronted with observations. We show that all scenarios encounter at least a few serious diffculties, if taken to represent a comprehensive model for the progenitors of all Type Ia supernovae (SNe Ia). Consequently, we tentatively conclude that there is probably more than one channel leading SNe Ia. While the single-degenerate scenario (in which a single white dwarf accretes mass from a normal stellar companion) has been studied in some detail, the other scenarios will need a similar level of scrutiny before any firm conclusions can be drawn.
Since the discovery of SN (supernova) 1987A, the number of Type II-peculiar SNe has grown, revealing a rich diversity in photometric and spectroscopic properties. In this study, using a single 15Msun low-metallicity progenitor that dies as a blue supergiant (BSG), we have generated explosions with a range of energies and 56Ni masses. We then performed the radiative transfer modeling with CMFGEN from 1d until 300d after explosion. Our models yield light curves that rise to optical maximum in ~100d, with a similar brightening rate, and with a peak absolute V-band magnitude spanning from -14 to -16.5mag. All models follow a similar color evolution, entering the recombination phase within a few days of explosion, and reddening further until the nebular phase. Their spectral evolution is analogous, mostly differing in line profile width. With this model set, we study the Type II-pec SNe 1987A, 2000cb, 2006V, 2006au, 2009E, and 2009mw. Their photometric and spectroscopic diversity suggest that there is no prototypical Type II-pec SN. These SNe brighten to maximum faster than our model set, except perhaps SN2009mw. The spectral evolution of SN1987A conflicts with other observations and with model predictions from 20d until maximum: Halpha narrows and weakens while BaII lines strengthen faster than predicted, which we interpret as signatures of clumping. SN2000cb rises to maximum in only 20d and shows weak BaII lines. Its spectral evolution is well matched by an energetic ejecta but the light curve may require asymmetry. The persistent blue color, narrow lines, and weak Halpha absorption, seen in SN2006V conflicts with expectations for a BSG explosion powered by 56Ni and may require an alternative power source. In addition to diversity arising from different BSG progenitors, we surmise that their ejecta are asymmetric, clumped, and, in some cases, not solely powered by 56Ni decay [abridged].
Type IIb supernovae (SNe IIb) present a unique opportunity for investigating the evolutionary channels and mechanisms governing the evolution of stripped-envelope SN progenitors due to a variety of observational constraints available. Comparison of these constraints with the full distribution of theoretical properties not only help ascertain the prevalence of observed properties in nature, but can also reveal currently unobserved populations. In this follow-up paper, we use the large grid of models presented in Sravan et al. 2019 to derive distributions of single and binary SNe IIb progenitor properties and compare them to constraints from three independent observational probes: multi-band SN light-curves, direct progenitor detections, and X-ray/radio observations. Consistent with previous work, we find that while current observations exclude single stars as SN IIb progenitors, SN IIb progenitors in binaries can account for them. We also find that the distributions indicate the existence of an unobserved dominant population of binary SNe IIb at low metallicity that arise due to mass transfer initiated on the Hertzsprung Gap. In particular, our models indicate the existence of a group of highly stripped (envelope mass ~0.1-0.2 M_sun) progenitors that are compact (<50 R_sun) and blue (T_eff <~ 10^5K) with ~10^4.5-10^5.5 L_sun and low density circumstellar mediums. As discussed in Sravan et al. 2019, this group is necessary to account for SN IIb fractions and likely exist regardless of metallicity. The detection of the unobserved populations indicated by our models would support weak stellar winds and inefficient mass transfer in SN IIb progenitors.
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