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 _ { 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 _ { hi } = 19 ^ { +4 } _ { -2 } M _ { \odot } ) , meaning that the statistical significance of the RSG Problem is less than 2 \sigma .
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 _ { hi } = 15.7 \pm 0.8 M _ { \odot } , giving the RSG Problem a significance of > 10 \sigma .
In this letter , we show that Kochanek ’ s 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 , Kochanek ’ s best fit becomes M _ { 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 .