Download - CV and pre-CV populations in the SDSS era Ulrich Kolb with Phil Davis (OU), Bart Willems (NWU)
CV and pre-CV populations in the SDSS era
Ulrich Kolbwith Phil Davis (OU), Bart Willems (NWU)
Post-common envelope binaries• PCEBs• create full population synthesis models• Davis, Kolb & Willems 2009
What’s new about it?
• cf. Willems & Kolb (2004), Politano & Weiler (2007)
• First proper present-day post-CE population model
• Compare in (Porb M1 M2)-space
• Focus on CE prescription and secondary star IMF
• There is a growing PCEB sample to compare against– here: Ritter & Kolb (2003; RKcat7.10 , 2008), with
2008 SDSS updates
Model assumptions• BiSEPS
• Classical magnetic braking (Mconv < M2 < 1.25 Msun), calibrated
• IMF of M2: same as for M1, or mass ratio correlated n(q) qν (ν=-1,0,1)
• common envelope: energy budget, or AM budget (Nelemans & Tout
2005)
Multi-panel representation of PCEB distribution over M2 - log Porb plane for different MWD
Model A
n(q)1αCE=1
Dependence on CE description (for n(q)=1)
Model AαCE=1
αCE(M2)2 proper
total energy
AM budget
WD mass1.1-1.4 Msun
IK Peg
Dependence on IMF of M2 (WD mass 0.4 - 0.5 Msun)
Summary of featuresObserved post-CE sample falls in populated regionsOutliers are probably not post-CE, except: IK Peg:
– needs αCE=3, i.e. additional energy sources
– description based on AM budget would work, too, but generates overabundance of long-period systems
Models extend to (and peak at) large M2 and long Porb where no systems are observed– May favour n(q) q-1 models– This also gives the lowest space densities (10-5 pc-3)– Selection effects or missing physics?
A selection effect? (with model A, n(q) q-1 )
All PCEBs
M2 < 0.50Msun
M2 < 0.35Msun
Using detection probability by Rebassa-Mansergas et al 2008
Reconstructing pre-CE parameters
0137-3457
A PDF for reconstructedCE values
Reconstructing pre-CE parameters
Red:Young PCEBs
Blue:M2<0.35Msun
Gravitational waves only
Green:M2>0.35Msun
Magnetic braking
SDSS CVs
Barker & Kolb 2003
Minimum period problem
For standard MB/GR evolutionary tracks convergeto universal track
Period bounce spikes add up
PPN
1)(
SDSS CVs (Gänsicke et al 2009)
New SDSS CVsvs model A
Kolb & Baraffe 1999
Conclusions
• All PCEB model populations extend to long periods and large companion masses – these are not seen in the observed sample
• There may be a relation CE (af)
• SDSS period spike too wide for GR only populations• Where is the age cut-off? • Consistent with remnant orbital braking a few times GR
below period gap