Matt Kistler homepage. Matthew Kistler A New Class of Luminous Transients and a First Census of Their Massive Stellar Progenitors
Why are dusty stars exploding?
The progenitors of SN 2008S and the luminous 2008 transient in NGC 300 were dust-enshrouded and seen only in the mid-infrared (MIR). Meanwhile, the MIR luminosities of the M85 transient (see here for the related circular) and SN 1999bw suggest that their progenitors were also highly obscured. As a class, these events were optically-faint compared to normal core-collapse supernovae. Whether true SNe or a new class of massive stellar eruptions, we argued that their rate is of order the rate of normal SNe. This fact is remarkable because very few massive stars in any galaxy, at any moment, have the characteristics of the progenitors of SN 2008S and NGC 300, which we showed by examining the MIR properties of massive stars in M33. We found that the fraction of all massive stars with colors consistent with the SN 2008S and NGC 300 progenitors is < 1/2000, with only ~10 similar objects in all of M33. That these transients are relatively common relative to SNe, while their progenitors are remarkably rare compared to massive stars, implies that the dust-enshrouded phase is a short-lived phenomenon in the lives of many massive stars, occurring only in the last < 10,000 years before explosion. We discussed the implications of this finding for the evolution and census of "low-mass" massive stars (i.e., 8-11 M_sun), connected with discussions of electron-capture SNe.
