Galactic Supernova RatePhysis 554 ProjectDecember 11, 2007Satoru InoueDepartment of PhysicsUniversity of WashingtonWhat is it?It's the time rate of supernova explosions in the Galaxy.Zwicky (1938) estimated the average time between 2 supernovae in an average “nebula” to be 460yr.Why bother?Stellar evolution−Star formation and death−SN mechanismWhy bother?Stellar evolution−Star formation and death−SN mechanismGalactic evolution−Nucleosynthesis−Remnants and other effects on surroundingsWhy bother?Stellar evolution−Star formation and death−SN mechanismGalactic evolution−Nucleosynthesis−Remnants and other effects on surroundingsGuide to Experiments−Neutrinos, cosmic rays−Gravitational wavesStrategies and ShortcomingsCount the # of events in the Milky Way−Too rare (last known event in late 17th c.)Strategies and ShortcomingsCount the # of events in the Milky Way−Too rare (last known event in late 17th c.)Count the # of events in other galaxies−Selection effectsStrategies and ShortcomingsCount the # of events in the Milky Way−Too rare (last known event in late 17th c.)Count the # of events in other galaxies−Selection effectsCount objects that could be SN remnants−How often do SNe turn into pulsars, etc.?Strategies and ShortcomingsCount the # of events in the Milky Way−Too rare (last known event in late 17th c.)Count the # of events in other galaxies−Selection effectsCount objects that could be SN remnants−How often do SNe turn into pulsars, etc.?Measure the amount of NS output−How much of it does one SN (and its progenitor) produce?Is it constant among galaxies?Is it constant among galaxies?SNe more common in spiral galaxies than in elliptical galaxiesEspecially type-II, which is closely related to star formation rateMannucci et. al. (2005)From extragalactic searchesYou can deduce the SN rate in the Milky Way by plugging in the luminosity for the SN rates for the same galaxy type.Total luminosity is ~2×1010LʘType is (probably) Sb⇒1.3±0.9/century (Cappellaro et. al. 1999)SN typesWe can also estimate the relative rates of SNe based on type.20% Type Ia10% Type Ib/c70% Type IIThe historical data is consistent. (with a small sample)The et. al. (2006)PulsarsPulsars−Galactic pulsar birth rate ~ 2.8/century−13~25% of CC SNe leave a black hole, and not a pulsar−Faucher-Giguère and Kaspi (2006) assumed all CC SNe left either a black hole or a pulsar, and derived CC SN rate ~ 3.2-3.7/century−Selection effects and ratio of SNe to pulsars unclearConstraints from NS60Fe−108Mʘ in the Galaxy, accumulated over 1010yrs−Ia produces about 0.6Mʘ, and CC produces about 0.1Mʘ−Upper limit of ~ 6 SNe/century (Tammann et. al. 1994)Constraints from NS26Al−Produced mainly by massive stars, and released into the surroundings by a core-collapse SN−β lifetime ~ 7.2×105yrs−CC SN rate = 1.9±1.1/centuryDiehl et. al. (2006)I said it doesn't work, but...Historically, we haven't seen as many SNe in the Galaxy as these rates indicate. This is most likely due to obscuration by the interstellar medium.With neutrino detectors, this shouldn't be a problem at all. So you CAN count the # of Galactic SNe.ProspectsBetter optical searches−Understand selection effects44Ti−Ejected by CC SN−Measurements and theory aren't consistent (The et. al. 2006)Neutrino detectionConsistency with models of galaxies and starsReferenceReviewsS. van den Bergh and G. A. Tammann, ARA&A 29:363-407 (1991)G. A. Tammann, W. Löffler, and A. Schröder, ApJS 92:487-493 (1994)SN searchesE. Cappellaro, R. Evans, and M. Turatto, A&A 351:459-466 (1999)E. Cappellaro et. al., A&A 430:83-93 (2005) F. Mannucci et. Al, A&A 433:807-816 (2005)F. Zwicky, ApJ 88:529-541 (1938)PulsarsC.-A. Faucher-Giguère and V. M. Kaspi, ApJ 643:332-355 (2006)NS outputR. Diehl et. al., Nature 439:45-47 (2006)D. Hartmann et. al., A&AS 97:219-220 (1993)L.-S. The et. al. A&A 450:1037-1050