Failed supernova

A '''failed supernova''' is an astronomical event in time domain astronomy in which a star suddenly brightens as in the early stage of a supernova, but then does not increase to the massive flux of a supernova. They could be counted as a subcategory of supernova imposters. They have sometimes misleadingly been called '''unnovae'''.<ref name=woosley>{{cite journal|bibcode=2012ApJ...752...32W|arxiv=1110.3842|title=Long Gamma-Ray Transients from Collapsars|journal=The Astrophysical Journal|volume=752|pages=32|last1=Woosley|first1=S. E.|last2=Heger|first2=Alexander|year=2012|issue=1 |doi=10.1088/0004-637X/752/1/32|s2cid=119240065}}</ref>{{failed verification|reason=reference doesn't say anything about the name being misleading|date=May 2024}}

==Overview== Failed supernovae are thought to create stellar black holes by the collapsing of a red supergiant star in the early stages of a supernova. When the star can no longer support itself, the core collapses completely, forming a stellar-mass black hole, and consuming the nascent supernova without having the massive explosion. For a distant observer, the red supergiant star will seem to wink out of existence with little or no flare-up. The observed instances of these disappearances seem to involve supergiant stars with masses above 17 solar masses.

Failed supernovae are one of several events that theoretically signal the advent of a black hole born from an extremely massive star, others including hypernovae and long-duration gamma-ray bursts.

==Structure and process== Theoretically, a red supergiant star may be too massive to explode into a supernova, and collapse directly into being a black hole, without the bright flash. They would however generate a burst of gravitational waves. This process would occur in the higher mass red supergiants, explaining the absence of observed supernovae with such progenitors.<ref name=SciAm-2015-11>{{cite journal |journal= Scientific American |title= Gone Without A Bang |author= Lee Billings |volume= 313 |issue= 5 |date= November 2015 |pages= 26–27 |doi= 10.1038/scientificamerican1115-26b |pmid= 26638393 |bibcode = 2015SciAm.313e..26B }}</ref><ref name=UT-2011-04-02>{{cite news |url= http://www.universetoday.com/84596/finding-the-failed-supernovae/ |title= Finding the Failed Supernovae |author= Jon Voisey |date= 2 April 2011 |publisher= Universe Today }}</ref><ref name=AstronomyMagazine-2016-09-27/>

==List of failed supernovae candidates== {|class=wikitable |- !| Event !| Date !| Location !| Notes !|  |- || NGC3021-CANDIDATE-1 || || {{nobr|NGC 3021}} {{RA|09|50|55.39}} {{DEC|+33|33|14.5}} || Disappearance of a 25-30 MSun F8 supergiant observed in archival HST data || <ref name=SciAm-2015-11/><ref name=2015MNRAS.453.2885R>{{cite journal |title= Gone without a bang: An archival HST survey for disappearing massive stars |doi= 10.1093/mnras/stv1809 |arxiv= 1507.05823 |bibcode= 2015MNRAS.453.2885R |publication-date= November 2015 |journal= Monthly Notices of the Royal Astronomical Society |volume= 453 |issue= 3 |pages= 2885–2900 |date= 21 July 2015 |last1= Reynolds |first1= Thomas M. |last2= Fraser |first2= Morgan |last3= Gilmore |first3= Gerard |doi-access= free |s2cid= 119116538 }}</ref> |- || N6946-BH1 || March 2009 || {{nobr|NGC 6946}} {{RA|20|35|27.56}} {{DEC|+60|08|08.2}} || Disappearance of an 18-25 MSun red supergiant || <ref name=SciAm-2015-11/><ref name=2015MNRAS.450.3289G>{{cite journal |title= The Search for Failed Supernovae with The Large Binocular Telescope: First Candidates |first1= J. R. |last1= Gerke |first2=C. S. |last2=Kochanek |first3=K. Z. |last3=Stanek |arxiv= 1411.1761 |bibcode= 2015MNRAS.450.3289G |doi= 10.1093/mnras/stv776 |publication-date= July 2015 |journal= Monthly Notices of the Royal Astronomical Society |volume= 450 |issue= 3 |pages= 3289–3305 |date= 6 November 2014 |doi-access= free |s2cid= 119212331 }}</ref><ref name=AstronomyMagazine-2016-09-27>{{cite magazine |url= http://www.astronomy.com/news/2016/09/this-star-was-so-massive-it-ate-itself-before-it-could-go-supernova |title= This star was so massive it ate itself before it could go supernova |author= Eugene Myers |date= 27 September 2016 |journal= Astronomy Magazine }}</ref> |- || M31-2014-DS1 || || {{nobr|Andromeda Galaxy}} || Disappearance of an 20 MSun yellow supergiant || <ref>{{Cite journal |last1=Beasor |first1=Emma R |last2=Smith |first2=Nathan |last3=Pearson |first3=Jeniveve |last4=Subrayan |first4=Bhagya |last5=Berger |first5=Edo |last6=Sand |first6=David J |last7=Strader |first7=Jay |date=2026-01-13 |title=The fate of the failed supernova candidate M31-2014-DS1 |journal=Monthly Notices of the Royal Astronomical Society |article-number=stag052 |language=en |doi=10.1093/mnras/stag052 |doi-access=free |issn=0035-8711}}</ref> |- |}

==References== {{reflist}}

==External links== {{wiktionary|failed supernova|unnova}}