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CV and pre-CV populations in the SDSS era. Ulrich Kolb with 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)
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CV and pre-CV populations in the SDSS era Ulrich Kolb with 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)1 αCE=1
Dependence on CE description (for n(q)=1) Model A αCE=1 αCE(M2)2 proper total energy WD mass 1.1- 1.4 Msun IK Peg AM budget
Summary of features • Observed post-CE sample falls in populated regions • Outliers 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 A PDF for reconstructed CE values 0137-3457
Reconstructing pre-CE parameters Red: Young PCEBs Blue: M2<0.35Msun Gravitational waves only Green: M2>0.35Msun Magnetic braking
Minimum period problem For standard MB/GR evolutionary tracks converge to universal track Period bounce spikes add up Barker & Kolb 2003
New SDSS CVs vs model A
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