Has any astronomer ever observed that after a specific star going supernova it became a Black Hole?

Question

Do we have any observational direct verification and historic record of a star after going supernova was turned into a Black hole?

Answer 1

I believe the best observational evidence for the creation of black holes at the end of a massive star's life are not found in those that explode as supernovae but in those thought to collapse directly to black holes. The problem with a supernova event is that it might leave a neutron star or it might leave nothing at all. If you simply see no evidence for a remnant after a supernova explosion then that could mean it has left a black hole or it could mean it has left nothing at all. It is possible for the exploding star to have been part of a binary, in which case one could deploy the techniques used to study massive compact binary systems (e.g. study the accretion disc or the reflex motion of the companion) to try and establish that a black hole exists, but that is very difficult when the supernovae are extragalactic and hence very distant.

Instead, we have the cases where a previously identified massive star "suddenly" disappears with no explosion. There is no alternative model (afaik) to explain the disappearance of a massive star other than it reaching the end of its life and collapsing directly into a black hole. Example candidates are reported by Reynolds et al. (2015), Adams et al. (2017) and Neustadt et al. (2021).

Answer 2

SN 1979C is a potential example, though it definitely depends on what counts as direct verification. See here for a paper which considers its bright and steady X-ray luminosity (tracked over 12 years) to be possible evidence for a stellar-mass black hole accreting material. However, they also consider an alternative explanation where the emissions come from a pulsar wind nebula.

SN 2022jli is another potential candidate. Oscillations in the light curve of the event are taken to imply the existence of a binary system consisting of a compact remnant and a companion star. See the paper here. In my skimming of the work it seems they do not really speculate on the exact nature of the remnant (whether it be a black hole or neutron star) other than a brief comment on p. 23 that if the remnant is a black hole, the event's Eddington luminosity ratio would be lower (and thus in my understanding more physically reasonable in a certain sense) than were the object a neutron star.