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تسجيل مستخدم جديدOn `On the Red Supergiant Problem: a rebuttal, and a consensus on the upper mass cutoff for II-P progenitors
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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 manifestation 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.
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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 upp
er 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).
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.
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