Galactic Rate

Physis 554 Project December 11, 2007 Satoru Inoue Department of Physics University of Washington What is it?

It's the time rate of supernova explosions in the .

Zwicky (1938) estimated the average time between 2 supernovae in an average “” to be 460yr.

Why bother?

− formation and death − SN mechanism

Why bother?

 Stellar evolution − and death − SN mechanism  Galactic evolution − Nucleosynthesis − Remnants and other effects on surroundings

Why bother?

 Stellar evolution − Star formation and death − SN mechanism  Galactic evolution − Nucleosynthesis − Remnants and other effects on surroundings  Guide to Experiments − , cosmic rays − Gravitational waves Strategies and Shortcomings

 Count the # of events in the − 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 − Selection effects

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 , 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 rate

Mannucci et. al. (2005)

From extragalactic searches

You can deduce the SN rate in the Milky Way by plugging in the luminosity for the SN rates for the same galaxy type.

10 Total luminosity is ~2×10 Lʘ Type is (probably) Sb

⇒1.3±0.9/century (Cappellaro et. al. 1999)

SN types

We can also estimate the relative rates of SNe based on type.

20% Type Ia 10% Type Ib/c 70% Type II

The et. al. (2006) The historical data is consistent. (with a small sample)

Pulsars

 Pulsars − Galactic birth rate ~ 2.8/century − 13~25% of CC SNe leave a , 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 unclear

Constraints from NS

 60Fe − 8 10 10 Mʘ in the Galaxy, accumulated over 10 yrs − 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 , and released into the surroundings by a core- collapse SN − β lifetime ~ 7.2×105yrs − CC SN rate = 1.9±1.1/century

Diehl 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 . With 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 − and theory aren't consistent (The et. al. 2006)  Neutrino detection  Consistency with models of galaxies and stars

Reference

Reviews S. van den Bergh and G. A. Tammann, &A 29:363-407 (1991) G. A. Tammann, W. Löffler, and A. Schröder, ApJS 92:487-493 (1994) SN searches E. 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) Pulsars C.-A. Faucher-Giguère and V. M. Kaspi, ApJ 643:332-355 (2006) NS output R. Diehl et. al., 439:45-47 (2006) D. Hartmann et. al., A&AS 97:219-220 (1993) L.-S. The et. al. A&A 450:1037-1050 (2006)