Jan. 19-21 2011

Participants: Joke Claeys, Ashley Ruiter, Silvia Toonen, (Nicki Mennekens; via Skype)

-Show that for the same assumptions (e.g., beta=1.0 or beta=0.5, eta=1.0) for the same initial M1, M2 and a all codes obtain the same final M1, M2 and a after the first mass transfer episode (ZAMS masses < 10 Msun). Proposed 4 new binary systems to test with 'conservative' code:

Ma=2.5 Mb=1.5 log(a)=1.25 or a=17.8 Rsun

Ma=2.5 Mb=1.5 log(a)=2.0 or a=100 Rsun

Ma=5.0 Mb=3.5 log(a)=2.0 or a=100 Rsun

Ma=5.0 Mb=3.5 log(a)=2.5 or a=316 Rsun

-Compare greyscale/scatter plots and distributions; be able to explain the differences between the plots for 1. populations at formation of first WD, and also 2. populations at formation of second WD (more easily done with codes which employ same/similar single star evolutionary tracks).

-Eventually: compare binary populations (e.g., SN Ia progenitor delay times) using our 'favourite assumptions' for mass accretion etc. (probably a second separate paper).

BINARIES: 

• 250,047 binaries for each run
• 2 main runs (for general binary population): 'eta'=1 for both; 'beta'=1.0, 0.5 [note: here eta=1 when (dJ_orb/J_orb = dM_tot/Mtot), beta is the fraction of mass transferred which is accreted by companion; 1 = fully conservative MT]. Super-Eddington accretion allowed!
• Z=0.02
• simple CE: alpha=1, lambda=1
• No tides, no magnetic braking
• Kroupa IMF (1993)
• M1_ZAMS = ~0.8 - 10 Msun
• “flat” mass ratio q, with M2=q*M1 where q_min=0.1/M1, q_max=1.0
• semi-major axis flat in log; 5 Run to 10000 Rsun

-Compared single stellar plots for various stages of evolution of:

• Mzams vs. mass
• Mzams vs. stellar radius
• Mzams vs. luminosity
• Mzams vs. (helium) core mass
• Mzams vs. (helium) core radius (Silvia, Joke; see 'things to do' below)

-The stages of evolution plotted were: start of ZAMS, HG, RG, HeCB, EAGB, TPGB, WD formation (for latter stage see Mi-Mf plot [to be uploaded] → good comparison between Mi-Mf for Hurley-based codes). some discrepancy between upper mass range which creates a WD (> 8 for Silvia and ~7.5+ for Joke, Ashley)

Overview of differences: Comparison

-Silvia and Joke …

• scatter plots: systems which make only 1 WD (and does not merge right away) in green; systems which make 2 WDs (and does not merge right away) in blue
• greyscale plots: agree on size bins and scaling!
• scatter/greyscale plots: Do not include any systems with NS or BH
• scatter/greyscale plots: M1 always on x-axis, where M1 is the FIRST star which forms a WD (but see double CE points below)
• scatter/greyscale plots: q is always = M_star_that_forms_2nd_WD / M_star_that_forms_1st_WD
• Double CE WDs: those that merge in DCE – throw out of plots. Or… keep them with special symbols?
• Double CE WDs: if they do not merge in CE, keep them and plot them at t1 and t2. Make clear somehow where they lie in the plot (e.g., for greyscale plot cannot use different symbols).
• Also: Nicki and Case A, Case B, Case C etc. mass transfer discussion; definitions of 'HG' and other stages: best to compare (single) stellar properties at a given stellar luminosity? “Start of Hertzsprung Gap” might be too ambiguous.

• Add to Joke/Silvia's comparison when put online
• Mzams vs. R_core/M_core plots for single stars: make clear 'what' the core represents physically
• Run/compare online those 4 binary systems (table on wiki - TO BE DONE by someone)
• Next meeting: Brussel, Late May - Early June?
• Include other groups eventually (Lev, Alexey, Bo…)
• later: SNe Ia comparison plots (histograms)