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تسجيل مستخدم جديدThe `Red Supergiant Problem: the upper luminosity boundary of type-II supernova progenitors
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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).
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The `Red Supergiant Problem describes the claim that the brightest Red Supergiant (RSG) progenitors to type II-P supernovae are significantly fainter than RSGs in the field. This mismatch has been interpreted by several authors as being a manifestati
on of the mass threshold for the production of black holes (BHs), such that stars with initial masses above a cutoff of $M_{rm hi}=17$M$_odot$ and below 25$M_odot$ will die as RSGs, but with no visible SN explosion as the BH is formed. However, we have previously cautioned that this cutoff is more likely to be higher and has large uncertainties ($M_{rm hi}=19^{+4}_{-2}M_{odot}$), meaning that the statistical significance of the RSG Problem is less than $2sigma$. Recently, Kochanek (2020) has claimed that our work is statistically flawed, and with their analysis has argued that the upper mass cutoff is as low as $M_{rm hi} = 15.7 pm 0.8M_odot$, giving the RSG Problem a significance of $>10sigma$. In this letter, we show that Kochaneks low cutoff is caused by a statistical misinterpretation, and the associated fit to the progenitor mass spectrum can be ruled out at the 99.6% confidence level. Once this problem is remedied, Kochaneks best fit becomes $M_{rm hi} =19^{+4}_{-2}M_{odot}$, in excellent agreement with our work. Finally, we argue that, in the search for a RSG `vanishing as it collapses directly to a BH, any such survey would have to operate for decades before the absence of any such detection became statistically significant.
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 ini
tial 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.
We examine the problem of estimating the mass range corresponding to the observed red supergiant (RSG) progenitors of Type IIP supernovae. Using Monte Carlo simulations designed to reproduce the properties of the observations, we find that the approa
ch of Davies & Beasor (2018) significantly overestimates the maximum mass, yielding an upper limit of Mh/Msun=20.5+/-2.6 for an input population with Mh/Msun=18. Our preferred Bayesian approach does better, with Mh/Msun=18.6+/-2.1 for the same input populations, but also tends to overestimate Mh. For the actual progenitor sample and a Salpeter initial mass function we find Mh/Msun=19.01-2.04+4.04 for the Eldridge et al. (2004) mass-luminosity relation used by Smartt et al. (2009) and Davies & Beasor (2018), and Mh/Msun=21.28_-2.28+4.52 for the Sukhbold et al. (2018) mass-luminosity relation. Based on the Monte Carlo simulations, we estimate that these are overestimated by 3.3+/-0.8Mh. The red supergiant problem remains.
We identify a pre-explosion counterpart to the nearby Type IIP supernova ASASSN-16fq (SN 2016cok) in archival Hubble Space Telescope (HST) data. The source appears to be a blend of several stars that prevents obtaining accurate photometry. However, w
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We present optical photometric and spectroscopic observations of the faint-and-fast evolving type Iax SN 2019gsc, extending from the time of g-band maximum until about fifty days post maximum, when the object faded to an apparent r-band magnitude m_r
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