Dust Formation By Failed Supernovae

We consider dust formation during the ejection of the hydrogen envelope of a red supergiant during a failed supernova (SN) creating a black hole. While the dense, slow moving ejecta are very efficient at forming dust, only the very last phases of the predicted visual transient will be obscured. The net grain production consists of ~0.01 solar masses of very large grains (10 to 1000 microns). This means that failed SNe could be the source of the very large extrasolar dust grains identified by Ulysses, Galileo and radar studies of meteoroid re-entry trails rather than their coming from an ejection process associated with protoplanetary or other disks.Comment: submitted to MNRA

Failed Supernovae Explain the Compact Remnant Mass Function

One explanation for the absence of higher mass red supergiants (16.5 Msun < M < 25Msun) as the progenitors of Type IIP supernovae (SNe) is that they die in failed SNe creating black holes. Simulations show that such failed SNe still eject their hydrogen envelopes in a weak transient, leaving a black hole with the mass of the star's helium core (5-8Msun). Here we show that this naturally explains the typical masses of observed black holes and the gap between neutron star and black hole masses without any fine-tuning of the SN mechanism beyond having it fail in a mass range where many progenitor models have density structures that make the explosions more likely to fail. There is no difficulty including this ~20% population of failed SNe in any accounting of SN types over the progenitor mass function. And, other than patience, there is no observational barrier to either detecting these black hole formation events or limiting their rates to be well below this prediction.Comment: Submitted to Ap