pcebs from the sdss testing disrupted magnetic braking
DESCRIPTION
PCEBs from the SDSS testing disrupted magnetic braking. Matthias Schreiber. Boris T. Gaensicke, John Southworth, S. Stylianos (Warwick) A. Rebassa-Mansergas (Valparaiso) M. Zorotovic-Fiebig, C. Tappert (PUC Santiago) L. Schmidtobreik (ESO) A. D. Schwope, A. Nebot Gomez-Moran (AIP). - PowerPoint PPT PresentationTRANSCRIPT
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PCEBs from the SDSS
testing disrupted magnetic braking
Matthias Schreiber
Tucson, March-2009
Boris T. Gaensicke, John Southworth, S. Stylianos (Warwick)
A. Rebassa-Mansergas (Valparaiso)A. Rebassa-Mansergas (Valparaiso)
M. Zorotovic-Fiebig, C. Tappert (PUC Santiago)
L. Schmidtobreik (ESO)
A. D. Schwope, A. Nebot Gomez-Moran (AIP)
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The orbital period distribution of CVs
Ritter & Kolb (2003)
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1983: Disrupted magnetic braking (DMB)
Paczynski & Sienkiewicz; Spruit & Ritter; Rappaport et al. (1983)
Two angular momentum loss mechanisms:
magnetic wind braking & gravitational radiation
MWB+GR GR
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DMB: believe it or not
Cons:- Spin down rates of low-mass
stars in open clusters (Sills et al. 2000)
- Large scale magnetic fields in fully convective stars(Donati et al. 2006)
Pros:- Mean mass transfer rates of CVs
(Townsley & Gaensicke 2008) - Donor star mass-radius relation
(e.g. Knigge 2006)
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Predicted PCEB fractions
Politano & Weiler (2006)
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WDMS and PCEBs from the SDSS
- SEGUE and SDSS identified ~2000 WDMS - We followed-up 285
- 111 PCEBs identified (~39%)
- 54 orbital periods measured (see next talk)
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PCEB fraction versus secondary spectral
type
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PCEB fraction versus secondary mass
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Comparing predictions and observations
Politano & Weiler (2006)
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- fast fully convective rotators in old field stars
- not a single early M fast rotator (Reiners et al. 2008)
- change in the magnetic field topology at ~M3.5(Donati et al. 2008)
Disrupted braking in single old field M dwarfs
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Conclusion
Disrupted braking confirmed!
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Remaining questions
Why does braking get disrupted?
How strong is AML below the gap?
Why is it different in young stars?
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For questions
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Gemini PCEB identifications (2007B, 2008A)
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3 good reasons to believe in DMB
- Mean mass transfer rates of CVs (Townsley & Gaensicke 2008)
- Expanded secondaries above the gap(e.g. Knigge et al. 2006)
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Selection effects
Bias towards short orbital periods
Bias towards low mass secondaries
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Disrupted braking in single field M dwarfs?