pcebs from the sdss testing disrupted magnetic braking matthias schreiber tucson, march-2009 boris...
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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)
The orbital period distribution of CVs
Ritter & Kolb (2003)
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
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)
Predicted PCEB fractions
Politano & Weiler (2006)
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)
PCEB fraction versus secondary spectral
type
PCEB fraction versus secondary mass
Comparing predictions and observations
Politano & Weiler (2006)
- 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
Conclusion
Disrupted braking confirmed!
Remaining questions
Why does braking get disrupted?
How strong is AML below the gap?
Why is it different in young stars?
For questions
Gemini PCEB identifications (2007B, 2008A)
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)
Selection effects
Bias towards short orbital periods
Bias towards low mass secondaries
Disrupted braking in single field M dwarfs?
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