In the Garden of Flux Variables - UVicastrofherwig/startalk... · evol~M-2.5 Result: WD formation...
Transcript of In the Garden of Flux Variables - UVicastrofherwig/startalk... · evol~M-2.5 Result: WD formation...
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In the Garden of Flux Variables
CC SNe .Ia's?
LRNe?
Kulkarni et al. 2007
LRNe=luminous red novae like the M85 transient
SN Ia
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brightness 1010 Lsun, Std candle
progenitor 1 or 2 white dwarfs:
mechanism mass transfer or merger
progenitor age ~109-10 yr evolution with z Little? Remnant (ns/bh) no Metals ejected Fe, Ni …
109 Lsun Not std candle massive star
core collapse:
~107 yr
(1+z) 2-4 : yes O, Ne, Si …
or
SNe Ia CC SNe
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SN Ia Progenitors - 2 Broad Classes
Single Degenerate - white dwarf + evolving secondary (M ~ 1.4 Msun at explosion)
Double Degenerate - 2 white dwarfs (Mtot >= 1.4 Msun at explosion)
Key point: white dwarf maximum mass M = 1.4 Msun (Chandrasekhar mass)
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D2 Cosmos ACS
imaging ~7 x 7
arcsec +-
Note diversity
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SN Ia rate depends on SFR
Mannucci et al 2006 Sullivan et al 2006
SNR/M
SFR/M
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Meaning
Only physics is evol-utionary timescales + SD assumption
Single component model – not A+B Same model for active and
passive Single free parameter
normalization - fSN Ia Continuous distribution of
delay times
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Evidence for SD vs DD Delay time distribution ~ 1/t
(continuous)
predicted #s of DDs vs SDs from pop models
obs of DD binaries that will merge
lack of X ray emission prior to explosion
no “Kasen effect”
super-Chandra events
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Other Obs
old pops – fast, faint Ia’s
stretch-L and colour-L relations
intrinsic dispersion 0.12 mag
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In the Garden of Flux Variables
TD=tidal disruption CN=classical novae
Bildsten 2008
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SN Ia progenitors
Why important? Among the most powerful explosions in the Universe
(next to GRBs) SNe Ia and cosmology Role in chemical evolution and gas dynamics
Scenario: exploding CO white dwarf near 1.4 Msun. Energy released (~0.5Msun CO --> 56Ni) No H in spectrum Light curve shape (radioactive decay) Presence in old stellar pops (what else could they be?)
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Two Basic Questions
What is the “delay time distribution” of SNe Ia? • What is the main sequence mass of SNe Ia
progenitors?
By what evolutionary path(s) do white dwarfs become SNe Ia?
Basic questions, but no clear answers …
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SN Ia rate depends on SFR
SFR½
€
cf . SNR /M = A + B(SFR /M)
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DTD ~ t-0.5±0.2
Independent of SD model or assumptions re efficiency t-0.5 what you expect for SD + constant conversion
efficiency
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Assume
Salpeter IMF tevol~M-2.5
Result: WD formation rate ~ t-0.5
Simple Model for WD
formation
±−
+−
−
∝
∝
⋅=
∝∝
−≅−≅
∝
∝
5.0
/)1(
1/1/1 ,
5.2,35.2 timescaleevol
fcn mass
τ
τττ
ττ
τ
τ
bba
bb
b
a
ddM
dMdN
ddN
ddMM
baM
MdMdN
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WD Formation Rate vs Time
Simple SFR(t) ~ t-η to allow for range of ages Correct ages
+1
-1 -1
+1
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SNLS-03D3bb (Howell et al. 2006) z=0.24, star-forming host
Most luminous SNIa ever discovered (MV=-20.0, 10 billion Lsun)
Lies off the stretch-L relation - too bright for its stretch s=1.13 by 4.4 sigma
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03D3bb
Requires 1.3 Msun of 56Ni to power light curve, 2Msun total mass
“normal” SNIa – 0.6 Msun of 56Ni
03D3bb is 2.2x brighter, therefore has 2.2x Ni mass
Detailed calculation using Arnett models agrees well
Mass > Chandra mass of 1.4 Msun!
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03D3bb
Low velocity of ejecta (8000 km/s)
Also implies super-Chandra mass
Conclusion: either (i) a rapidly rotating WD, or (ii) WD-WD merger
Implications for cosmology (this object was not used in Astier et al 2006)