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Matthias Schreiber

Constraining close binaries evolution with SDSS/SEGUE: a representative sample of white dwarf/main sequence binaries. Matthias Schreiber. ESO, May 4th, 2006. The questions in compact binary evolution are…. … the questions that everyone of us has. Where will I go to?. Where do I come from?.

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Matthias Schreiber

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  1. Constraining close binaries evolution with SDSS/SEGUE:a representative sample of white dwarf/main sequence binaries Matthias Schreiber ESO, May 4th, 2006

  2. The questions in compact binary evolution are…

  3. … the questions that everyone of us has Where will I go to? Where do I come from? How much time have I left? And what am I supposed to do here?

  4. Motivation • Understanding the formation and evolution of close binaries: • Supernova Ia • Binary millisecond pulsars • Galactic black hole candidates • Short gamma-ray bursts • Catalysmic Variables • Part of stellar evolution • …

  5. The evolution into close binaries How strong is AML due to magnetic braking? Parameter: “CE-efficiency” “binding energy parameter”

  6. Example: Our non-understanding of the evolution of CVs Porb is typically the best determined parameter of a CV Ritter & Kolb (2003) V7.3: 531 systems

  7. MWB+GR GR Flashback – 1983: Disrupted magnetic braking Two angular momentum loss mechanisms: magnetic wind braking & gravitational radiation Paczynski & Sienkiewicz; Spruit & Ritter; Rappaport et al. (1983)

  8. Predictions of the standard CV evolution model - Lack of CVs in the 2-3h Porb range

  9. The period gap

  10. - Paucity of CVs in the 2-3h Porb range The standard model: Predictions - Minimum orbital period at ~65min

  11. Period bouncing

  12. The orbital period minimum 80 min!

  13. - Paucity of CVs in the 2-3h Porb range X - Minimum orbital period at ~65min The standard model: Predictions - Pile-up at Pmin

  14. Population syntheses: The period minumum Kolb & Baraffe (1999)

  15. The orbital period minimum 80 min!

  16. - Paucity of CVs in the 2-3h Porb range X X - Minimum orbital period at ~65min - Pile-up at Pmin The standard model: Predictions - 99% of all CVs have Porb<2h

  17. 55=10% 207=39% 250=51% The orbital period distribution

  18. - Paucity of CVs in the 2-3h Porb range X X - Minimum orbital period at ~65min - Pile-up at Pmin X - 99% of all CVs have Porb<2h - CV space density ~ X Observed ~ The standard model: Predictions

  19. Additions to the standard model (incomplete) • Hibernation (Shara et al. 1986) Large number of detached white dwarf/red dwarf binaries • The binary age postulate (Schenker & King 2002) Large number of detached white dwarf/red dwarf binaries • Alternative angular momentum loss rates • (e.g. Andronov et al. 2003, Taam et al. 2003) Too low accretion rates (Andronov), circumbinary discs (Taam)

  20. … what else can we do? • Overcome observational biases and provide a statistically • representative sample of close binaries to constrain the • theories of CE-evolution and magnetic braking. • Detached white dwarf/main sequence binaries are the best • class of systems for this task because they are: • intrinsically numerous • clean (no accretion) • accessible with 2-8m telescopes • well understood

  21. Members of the WD/MS population • long orbital period systems i.e. WD/MS that will never • interact • Post-common envelope binaries (PCEBs) i.e. WD/MS which • went through a CE-phase • pre-CVs i.e. PCEBs which will become a CV • in less than a Hubble-time

  22. Constraining CE-evolution with WD/MS binaries Two algorithms to determine the final separation are proposed: 1. Energy conservation (Paczynski 1976) 2. Angular momentum conservation (Nelemans & Tout 2005) Reconstructing the CE-phase for a representative sample will tell us if one algorithm works!!

  23. How large is the gap? • A large gap in the WD/MS distribution will indicate a low • efficiency of using the binary energy (angular momentum) • to expel the envelope. • No gap will indicate that the CE-phase is very efficient in • removing the giants envelope. (Willems & Kolb 2004)

  24. Is magnetic braking disrupted? PCEBs can tell us: Politano & Weiler (2006)

  25. The age of WD/MS systems (Schreiber & Gänsicke 2003)

  26. The evolution of close WD/MS systems AML Twd (age), Porb PCE, PCV, timescale (Schreiber & Gänsicke 2003)

  27. The contact orbital periods (Schreiber & Gänsicke 2003)

  28. Selection effects in the pre-SDSS sample (Schreiber & Gänsicke 2003)

  29. Selection effects in the pre-SDSS sample PG: U-B<-0.46 (Schreiber & Gänsicke 2003) • Extremely biased sample: • hot white dwarfs = young systems (t<108yr) • low mass companions = will start mass transfer at Porb<4h

  30. WD/MS systems in SDSS I and SEGUE • Stars (white dwarfs, main sequence)

  31. WD/MS systems in SDSS I and SEGUE • Stars (white dwarfs, main sequence) • Quasars

  32. WD/MS systems in SDSS I and SEGUE • Stars (white dwarfs, main sequence) • Quasars • WD/MS from SDSS I

  33. WD/MS systems in SDSS I and SEGUE • Stars (white dwarfs, main sequence) • Quasars • WD/MS from SDSS I • Model WD (8-40kK) + MS (K0-M8)

  34. WD/MS systems in SDSS I and SEGUE • Stars (white dwarfs, main sequence) • Quasars • WD/MS from SDSS I • Model WD (8-40kK) + MS (K0-M8) • SDSSII / SEGUE WD/MS candidates • (4 fibers per field)

  35. SEGUE WD/MS spectra Current success rate is ~70%: number one in SEGUE!!! • Immediate objectives: • Space density • Fraction of magnetic systems • Age of the population • Evolutionary time scale Vision: Follow-up observations of the entire sample to constrain the CE-phase and magnetic braking

  36. Status of follow-up observations • Calar Alto 3.5 (first pilot study, performed) • Calar-Alto DDT (first orbital period, performed) • WHT (6 nights July 2006, received) • Calar-Alto Large Program (proposed 03.2006) • ESO (pilot –study, proposed 03.2006) • ESO (Large program, planed 09.2006)

  37. CA-observations Feb. 2006 In agreement with BPS predictions of 15-20%

  38. CA-Observations, March 2006 A 10 hrs orbital period PCEB:

  39. Conclusions • A representative sample of WD/MS binaries will allow • to significantly progress with our understanding of • close binary evolution: • - constrain the CE-phase • - estimate the strength of magnetic braking • - test the disrupted magnetic braking hypothesis • The pre-SDSS sample and the systems identified in SDSS I • are strongly biased. • We run a very successful SEGUE project and will identify • the required representative sample until 2008 • First follow-up observations give promising results!!

  40. Mission Members: • The Collaboration: • PI: Matthias Schreiber (Valparaiso) • Boris Gaensicke (Warwick) • Axel Schwope (Potsdam) • Ada Nebot (Potsdam) • Robert Schwarz (Potsdam) • Alberto (Warwick) • Pablo Rodriguez-Gil (IAC) • Nikolaus Vogt (Valparaiso)

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