Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.arcetri.astro.it/~filippo/snrate08/Contributions_files/ruiter.pdf Дата изменения: Tue Jun 3 14:58:47 2008 Дата индексирования: Tue Nov 24 19:29:42 2009 Кодировка: Поисковые слова: supernova

Formation Channels of Potential SN Ia Progenitors
delay times & rates of various scenarios

Ashley Ruiter (New Mexico State University) K. Belczynski (LANL/NMSU)

Supernova Rates 2008 Florence, Italy, May 19-22


Binary Evolution:
population synthesis model

· · · · ·

Use StarTrack population synthesis code (Belczynski et al. 2008) to evolve stellar populations Evolve single and binary stars incorporating analytical formulae for stellar evolution and most recent prescriptions for accretion onto WDs (Nomoto et al. 2007) Consider: common envelope (CE) evolution, metallicity, binary fraction, IMF, SFR Calibration: use Galactic stellar mass (6 x 1010 M SNe Ia event criteria: )


SN Ia Formation Channels
(Chandrasekhar Mass)

DDS: CO+CO, C0+He, He+He WD-WD merge with Mtot > 1.4 M SDS: CO/He WD + MS/Giant accreting binary (WD reaches 1.4 M ) AM CVn: C0/He WD accretes to 1.4 M from He-rich companion (WD or helium star) CE Merger (SN IIa): WD + core of AGB star merge in a Common Envelope with Mtot > 1.4 M (Livio & Riess 2003)


Calibration: SN Rates
two model galaxies

· · · · · ·

Two simple galaxy models: spiral & elliptical Spiral Galaxy: Z=0.02, constant star formation history for 10 Gyr Elliptical Galaxy: Z=0.002, starburst at t=0 Kroupa IMF (0.08 - 150 M )

Standard CE prescription = 1 (Webbink 1984) Initial q flat; initial separation flat in log, 50% binary fraction


SN Rates
Elliptical channel DDS SDS AM CVn Type II + Ib/c efficiency (per binary) 0.3 % of binaries 0.01 % of binaries 0.01 % of binaries 1% + 0.8% of binaries Spiral

SNIa/yr @ 10 Gyr SNIa/yr @ 10 Gyr Z=0.002,starburst Z=0.02, cons.SFR

4x10-4 ~10 ~10 0
-5

2x10-3 5x10-5 8x10-5 ~10
-2

-5


observed rate

0.002 DDS/yr DDS AMCVn SDS

Observed Galactic rate: 0.004 ± 0.002 SNIa/yr (E. Cappellaro)


Model Delay Time Distributions
ZAMS binary formation to SN Ia


Predicted Delay Times From Burst of SF

Dominant mechanisms: DDS: GR timescale CO-CO only; DTmin=50 Myr. AMCVn: shortest DTD; GR drives MT rates (small a). SDS: mostly Giant-WD; MS-WD have largest overall DT take long time to accrete enough H.


Summary + Discussion

· · ·

The SDS channel appears to contribute very little to SNe Ia in terms of rates DDS is more than an order of magnitude more common than SDS in our models and is marginally constant with observed rates Additionally, the DDS exhibits a wide range of delay times (prompt as well as tardy, and in between)


Predicted Delay Times
(5 scenarios)

CE merger scenario (CEMS): most prompt channel, could explain the few SNe Ia with H but is likely too eficient in our models