text:   Birth in the Pair-instability Mass Gap",8,"['<LINK>  Perfect timing for new paper on a new type of transient. Punchline: while kilonovae signal the birth of light black holes (from NS mergers), ""Super-kilonovae"" may accompany the birth of the most massive (stellar mass) LIGO BHs.  @astroVAV @amanagarawal20', ""Basic idea: scale up collapsars (progenitors of long GRBs) to extremely massive stars above the pair-instability mass gap.  When trying to feed a newly formed BH at such high rates, much of the in-falling star doesn't make it in, instead being ejected in accretion disk outflows."", 'We estimate these neutron-rich outflows generate r-process elements, with  yields ~10s of Msun (~100 times higher than in neutron star mergers like GW170817 and ~10 times higher than ""ordinary"" low-mass collapsars).', 'This results in a lower final mass BH than one would predict from the progenitor He core, allowing to fill-in the pair-instability mass-gap ""from above,"" and providing a speculative channel for generating massive BBH like the components GW190521. https://t.co/txzEAL7dEe', 'This large mass ejection powers a radioactively-powered transient much brighter and longer-lasting than ordinary kilonovae, similar to SNe but much redder (near-IR peak); hence ""Super-kilonova"".  Roman Space Telescope could potentially discover these transients out to z ~ 1. https://t.co/omoLHbqK11', 'The nominal BH accretion rates achieved are also significantly higher than ordinary collapsars, allowing to power particularly energetic gamma-ray bursts.  SuperKN should be searched for following the most energetic GRBs by JWST.', 'Gravitational instabilities in these massive disks could also generate GW emission accessible to 3G detectors; unlike in the ""chirp"" in CO mergers, the GW signal decreases in frequency with time as the disk grows in radius (we term ""sad trombone"", to borrow a term from the FRBs). https://t.co/QSmoC79fML', 'Overall a fun ""ideas"" paper to work out, which puts together some ideas already germinating out there in the community, and completed by a talented group of young researchers, most of which overlapped here at Columbia/CCA over past few years.']",21,11,2050