Observational population studies of post CE binaries

Boris Gänsicke
Observational population
studies of post CE binaries
Outline
1. Looking back ~10 years
2. Post-common envelope binaries from SDSS (+ CSPNe)
- identification, stellar parameter
- orbital period distribution
- αCE , recombination energy & magnetic braking
- low mass WDs
- SNIa progenitors: something different
3. Single He-core WDs – link to planetary systems?
4. Extremely low-mass WDs
5. Magnetic fields
6. Subdwarfs in binaries
Theory is good – but need some observational
tests
uble degenerate WD binaries – popular as Ia progenitor candidates,
• large fraction are single lined binaries ⇒ only 1 mass
• complex evolution, 2CEs
• rare, 14 known in 2001
Nelemans et al. 2001, A&A 365,
491
Theory is good – but need some observational
tests
D+MS binaries:
• accurate parameter for both stellar components
• simple evolution, 1 CE
• also rare, 30 in 2003,
• seriously biased: young WDs, low-mass companions
Blue-excess surveys
Schreiber & Gänsicke 2003
A&A 406, 305
SDSS multi-colour revolution
Rebassa-Mansergas et al. 2010,
MNRAS 402, 620
Smolcic et al. 2004, ApJ 615,
L141
>2300 WD+MS binaries
Raymond et al. 2003, AJ 125, 261; Silvestri et al. 2006, AJ 131, 1674S & 2007, AJ 134,
741; Augusteijn et al. 2007, MNRAS 382, 1377R; Heller et al. 2009, A&A 496, 191;
Rebassa-Mansergas et al. 2007, MNRAS 382, 1377 & 2010, MNRAS 402, 620 & 2012,
MNRAS 419, 806R & 2013, MNRAS 433, 3398; Liu et al. 2012, MNRAS 419, 806, Wei et
al. 2013, MNRAS 431, 1800
+ Ren et al. 2013, AJ 146, 82R (LAMOST, see her talk later today)
Do not believe and WD+MS binary out in the
literature
Rebassa-Mansergas et al. 2010, MNRAS 402,
620
Stellar parameters: spectral decomposition
⇒ MS spectral type (+/- 1/2 class)
Spectral type-mass-radius relation:
⇒ MS mass & radius (~20-50%)
Stellar parameters: WD Balmer line fit
⇒ Teff & log g
Evolutionary models,
mass-radius relation:
⇒ WD mass & radius
(~10-30%)
⇒ WD cooling age
You need more precision? Eclipsing WD+MS
binaries
2009: seven eclipsing WD+MS
binaries
2013: 49 eclipsing WD+MS binaries
Masses & radii to a few %,
see Steven Parsons talk
Pyrzas et al. 2009, MNRAS 394, 978
Nebot Gomez-Moran et al. 2009, A&A 495,
561
Drake et al. 2010, arXiv:1009.3048
Becker et al. 2011, ApJ 731, 17
Law et al. 2012, ApJ 757, 133L
Pyrzas et al. 2012, MNRAS 419, 817
Almenara et al. 2012, MNRAS 420, 3017A
Parsons et al. 2013, MNRAS 429, 256
Radial velocity follow-up:
~1/3 of SDSS WD+MS binaries are PCEBs
Orbital period distribution
Nebot Gomez Moran et al. 2011, A&A
536, 43
Radial velocity bias: small, and accountable
Nebot Gomez Moran et al. 2011, A&A
536, 43
Orbital period distribution
Nebot Gomez Moran et al. 2011, A&A
536, 43
Observations vs theory
Nebot Gomez Moran et al.
2011
A&A 536, 43
Willems & Kolb 2004,
A&A 419, 1057
Binary central stars in planetary nebulae
e.g. De Marco et al. 2004, ApJ 602, L93 & 2008, AJ 136, 323 & 2013, MNRAS 428,
2118; Miszalski et al. 2009, A&A 496, 813 & 2013, MNRAS 428, L39; Jones et al.
2014, A&A 562, 89
Orbital periods of CSPNe vs WD+MS
Miszalski et al. 2009, A&A 496, 813
Hillwig 2013, ASPC 469, 277
A wider perspective
HST/ACS imaging of WD+MS binaries
Farihi et al. 2010, ApJS 190, 275
Perfect agreement with SDSS WD+MS RV
results
Farihi et al. 2010, ApJS 190, 275
Nebot Gomez Moran et al.
2011
A&A 536, 43
Reconstruction: α≈0.2-0.3
No dependence on M2 (but the
sample only spans 0.1-0.4M๏)
Zorotovic et al. 2010, A&A 520, 86
⇒ Need WD+MS binaries with earlier
companions (see Alberto
Rebassa-Mansergas talk)
See also de Marco et al. 2011, MNRAS 411,
2277
Long-period WD+MS binaries: Recombination
energy?
Not necessary for these two systems
Rebassa-Mansergas et al. 2012, MNRAS 423, 320
Confirmation of (disrupted) magnetic braking
fully
convective
Schreiber et al. 2010, A&A 513, L7
Mass loss: ~0.8-8Mʘ stars become
~0.6-1.4Mʘ WDs
CO-cores
He-cores
ONe-cores,
mergers
Liebert et al. (2005, ApJS 156, 47)
⇒ significant mass
loss!
Direct proof of the CE origin of He-core WDs
Rebassa-Mansergas et al. 2011, MNRAS 413, 1121
Direct proof of the CE origin of He-core WDs
Rebassa-Mansergas et al. 2011, MNRAS 413, 1121
Mass dependence on Porb
PCEBs with He core WDs have shorter orbital periods
Zorotovic et al. 2011, A&A 536, L3
Cataclysmic variables
??
Common knowledge: the?WD mass
should
be eroded by classical nova eruptions
(e.g.
CVs versus pre-CVs and PCEBs
<Mwd> = 0.83 ± 0.23
M๏
<Mwd> = 0.67 ± 0.21
M๏
<Mwd> = 0.58 ± 0.20
M๏
Zorotovic et al.
2011,
SNIa progenitors – something different
• Either the present-day CVs
descended from progenitors
that were more massive than
those of the present-day pre-CV
population ... And likely
underwent thermal-timescale
mass transfer.
(search for WD + FG binaries, see
Alberto Rebassa-Mansergas
talk)
• Or CV white dwarfs grow in
mass (against most CN
theory)
⇒ Both options will produce
viable SNIa progenitors
see Toonen et al.
arXiv:1403.4797
for an alternative discussion
Mass loss: ~0.8-8Mʘ stars become
~0.6-1.4Mʘ WDs
CO-cores
He-cores
ONe-cores,
mergers
A fraction of He-core WDs
shows no radial velocity
variability ... apparently
single stars
Nelemans & Tauris 1998,
A&A 335, L85: Giant planets
Liebert et al. (2005, ApJS 156, 47)
A He core WD with a planetary debris disc
Close-in giant planet + rocky material further out
Farihi et al. 2012, MNRAS 421, 1635
Extremely low-mass WDs in double-degenarate
binaries
~60 binaries, including five eclipsing systems
SDSSJ0651+2844
Porb=12.75min
Brown et al. 2010, ApJ 723, 1072 & 2011, ApJ 737, L23 & 2012, ApJ 744, 142 & 2012, ApJ 751,
141 & 2013, ApJ 769, 66; Kilic et al. 2011, ApJ 727, 3 & 2011, MNRAS 413, L101 & 2012, ApJ 751,
141 & 2014, MNRAS 438, L26 ; Kawka et al. 2010, A&A 516, L7K; Steinfadt et al. 2010, ApJ 716,
L146; Marsh et al. 2011, ApJ 736, 95, Parsons et al. 2011, ApJ 735, L30; Vennes et al. 2011, ApJ
737, L16
Extremely low-mass WDs
Several ELM white dwarfs are pulsating
Hermes et al. 2012, ApJ 750, L28 &
2013, ApJ 765, 102 & 2013, MNRAS
436, 3573
⇒ Core & envelope mass
and composition from
asteroseismology
Where do magnetic WDs get their field from?
• Liebert et al. 2005, AJ 129, 2376: Where Are the Magnetic
White
dwarfs with Detached, Nondegenerate
Companions?
• >2300 WD/MS binaries ... And not one with a magnetic WD
... not one...?
Simulated magnetic WD + MS spectra
Easy to recognise!
Silvestri et al. 2007, AJ 134,
... not one ...?
... ST LMi, a polar, in a low state ...
Schmidt et al. 2005, ApJ 630, L173; Debes et al. 2006, ApJ 647,
L147; Howell et al. 2008, AJ 136, 2541; Breedt et al. 2012, MNRAS
423, 1437
Dynamos in the CE phase? Potter & Tout 2010, MNRAS 402, 1072
But see Steven Parson’s talk
Subdwarfs in binaries & MUCHFUSS
Geier et al. 2011, A&A 526, 39 & 2011, ApJ 731, L22 & 2011,
A&A 530, 28 & 2014, A&A 562, 95; Ostensen et al. 2013, A&A
559, 35
See Stephan Geier’s talk on Friday and Thomas Kupfer’s poster
Conclusions
• The past decade has seen an explosion in the number
of known post-common envelope binaries.
• Several high-fidelity samples with accurate stellar and
binary parameter are in the works (WD+MS, CSPNe,
WD+WD, sdB+MS, sdB+WD...)
The future looks bright
• GAIA will provide volume-limited samples of PCEBs
• LSST & GAIA ⇒ 100s of eclipsing systems
• WEAVE & 4MOST ⇒ industrial scale spectroscopy

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