Constraining close binaries evolution with SDSS/SEGUE:
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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

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 in compact binary evolution are…


The questions that everyone of us has

… 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?


Motivation

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


The evolution into close binaries

The evolution into close binaries

How strong is AML due

to magnetic braking?

Parameter: “CE-efficiency”

“binding energy parameter”


Example our non understanding of the evolution of cvs

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


Flashback 1983 disrupted magnetic braking

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)


Predictions of the standard cv evolution model

Predictions of the standard CV evolution model

- Lack of CVs in the 2-3h Porb range


The period gap

The period gap


The standard model predictions

- Paucity of CVs in the 2-3h Porb range

The standard model: Predictions

- Minimum orbital period at ~65min


Period bouncing

Period bouncing


The orbital period minimum

The orbital period minimum

80 min!


The standard model predictions1

- Paucity of CVs in the 2-3h Porb range

X

- Minimum orbital period at ~65min

The standard model: Predictions

- Pile-up at Pmin


Population syntheses the period minumum

Population syntheses: The period minumum

Kolb & Baraffe (1999)


The orbital period minimum1

The orbital period minimum

80 min!


The standard model predictions2

- 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


The orbital period distribution

55=10%

207=39%

250=51%

The orbital period distribution


The standard model predictions3

- 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


Additions to the standard model incomplete

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)


What else can we do

… 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


Members of the wd ms population

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


Constraining ce evolution with wd ms binaries

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!!


How large is the gap

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)


Is magnetic braking disrupted

Is magnetic braking disrupted?

PCEBs can tell us:

Politano & Weiler (2006)


The age of wd ms systems

The age of WD/MS systems

(Schreiber & Gänsicke 2003)


The evolution of close wd ms systems

The evolution of close WD/MS systems

AML

Twd (age), Porb

PCE, PCV, timescale

(Schreiber & Gänsicke 2003)


The contact orbital periods

The contact orbital periods

(Schreiber & Gänsicke 2003)


Selection effects in the pre sdss sample

Selection effects in the pre-SDSS sample

(Schreiber & Gänsicke 2003)


Selection effects in the pre sdss sample1

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


Wd ms systems in sdss i and segue

WD/MS systems in SDSS I and SEGUE

  • Stars (white dwarfs, main sequence)


Wd ms systems in sdss i and segue1

WD/MS systems in SDSS I and SEGUE

  • Stars (white dwarfs, main sequence)

  • Quasars


Wd ms systems in sdss i and segue2

WD/MS systems in SDSS I and SEGUE

  • Stars (white dwarfs, main sequence)

  • Quasars

  • WD/MS from SDSS I


Wd ms systems in sdss i and segue3

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)


Wd ms systems in sdss i and segue4

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)


Segue wd ms spectra

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


Status of follow up observations

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)


Ca observations feb 2006

CA-observations Feb. 2006

In agreement with BPS predictions of 15-20%


Ca observations march 2006

CA-Observations, March 2006

A 10 hrs orbital period PCEB:


Conclusions

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!!


Mission members

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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