The a formalism for the common envelope interaction

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The a formalism for the common envelope
interaction

• Orsola De Marco
• American Museum of Natural History
• (in 15 days at Macquarie University)

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What giants do when they are tickled

• Orsola De Marco
• American Museum of Natural History
• (in 15 days at Macquarie University)

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Can planets make planetary nebulae?

• Orsola De Marco
• American Museum of Natural History
• (in 15 days at Macquarie University)

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Outline

• The binary problem in PNe.
• The common envelope interaction.
• The CSPNe from common envelope interactions.
• The PNe from common envelope ejections.
• The importance of the common envelope efficiency
  parameters aCE for the PN problem.
• The future of the observational hunt for
  binaries.
• PlaN-B update.

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The binary problem in PNe

• Binaries offer an appealing method to craft
  many/most PNe.
• With 30 of all stars orbited by a binary
  companion close enough to interact, they is
  also a plausibility arguments.
• However how do we support this claim
  observationally?

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The common envelope interactionTop-of-the-AGB
giant and 0.1 Mo companion
Density greyscale Orbital Plane
Density greyscale Perpendicular Plane
(De Marco et al. 2003)
Iso-Density Surface of the Two Cores
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The common envelope interactionENZO simulation
PhD Thesis of Jean-Claude Passy
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After the common envelope interaction
Short-period binary
Merged star
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Common envelope PNe are common

• (17 /- 5) of all PN have a post-CE binary in
  the middle (Miszalski et al. 2009)
• One in 5 PNe are ejected CEs.
• So the CE channel is interesting.
• For post-CE PNe we actually know theejection
  mechanism!

Image by Dana Berry (STScI)
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PNe from common envelopes should be different

• Ejected common envelopes 1-10 year ejection.
  Regular ejection 1000 yr for the ejection.
• Teff of CSPN increased suddenly transition
  time shortened PN should have switched on
  faster.
• AGB was interrupted C/O should be on average
  lower.
• Shapes expected axi-symmetry. Soker (1997)
  elliptical PNe Nordhaus Blackman 2006
  1. Massive torus for surviving systems,
  2. Bipolar with no torus for non surviving
  systems, 3. Jets if companion makes a disk
  around primary.

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PNe from common envelopes are they different?

• It is observed that the post-CE PNe have smaller
  ionized masses and are more excited.

Frew 2008
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PNe from common envelopes are they different?

• Shapes observed several, but many could be
  bipolar and jets are somewhat common

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Could common envelope PNe be more common?

• (17 /- 5) of all PN have a post-CE binary in
  the middle Plt3days.
• Biases
• No Bond bias.
• Yes
• Systems P gt 2 weeks?
• Smaller companions?
• Radiation transport from hot to cool side
  lessening the contrast.

Miszalski et al. 2009
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The common envelope efficiency parameter ?CE
? Ebin ?CE ?Eorb
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The energy needed and the energy available.
? Ebin ?CE ?Eorb
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How do we use aCE Population synthesis
aCE 0.3
Progenitor population binary fraction (57) and
period distribution Progeny population binary
fraction (55) and period distributionMoe De
Marco (2006, 2008)
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Methods for the calculation of aCE

• Simulations
• Observed post-CE systems
• (Population synthesis)

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The calculation of aCE simulations
Yungelson equation
aCE 1.0 1.2 (Han formalism)
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The calculation of aCE real systems
e.g. BE UMa Mc 0.70 0.07 M2 0.36 0.07
P 2.29 days
e.g. BE Uma eclipsing binary. Af from Period
MWD from Mc adding 0.019 /- 0.013 Mo MMS from
MWD and the IFMR. M1 from MMS multiplying by
0.7/- 0.1 Me from Mc L from Mc R from L and M1
(and R Ai)
Me
Mc
M2
Mc
M2
Me
Mc
Me
R
Af
Ai
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What does ?CE depend on?
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Interpretation aCE gt 1
How can aCE be larger than unity? Mass-losing
giants expand. Companions induce initial
mass-loss, which stimulates expansion. This
mean giants help to unbinding their own
envelope. Because of the added energy source,
which is not explicitlyaccounted for the in the
aCE equation, the calculated ?CE gt 1.
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Interpretation anti-correlation
Why do small companions (low values of q) seem
to get more help from the star (larger values
of ?CE)? Smaller companions penetrate more
slowly star has time to react.
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Conclusion of the CE study

• The study of the details of the interaction
  through a careful evaluation of aCE is brining
  us an understanding that smaller companion than
  otherwise suspected can eject the envelope and
  be undetected by our survey technique.
• We know this is true because of the detection of
  a BD around a WD by Maxted et al. (2006).
• If we could detect such companions we would raise
  the total fraction of PN from CEs by gt10.
• Companions, even small, can induce a low mass
  post-AGB star (Mlt0.55 Mo) to make a PN by
  shortening the transition time.This arguments
  predicts a handful of PNe in GCs. Maybe even the
  Sun will make a PN.

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Fraction of PN influenced by a companion? Finding
companions
Direct detections of companions near-IR surveys
to find how many intermediate separations
companions there are. Future detections direct
imaging of AGB stars for companionswith
separations between a few to 100 AU.
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Fraction of PN influenced by a companion? Finding
proxies
If potentially important companion detections are
beyond our capabilities, we need to find indirect
markers. Disks are the best proxy because a
measurement of angular momentum goes a long way
towards demonstrating pre-requisites for their
formation.
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Observational testsA historical interlude
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The bottom line

• Key publication Nordhaus Blackman 2006,
  Nordhaus et al. 2007 it is hard to maintain
  magnetic fields in single stars.
• Binaries offer a more plausible way to shape and
  possibly even to instigate the superwind.
• The test is not just observing companions and
  fields.
• We need meaningful models that tie all the
  elements together.

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La Palma 2007
Sydney 2009
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l and the core boundary
R
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The meaning of l
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How we calculate lambda l
The dilemma of the core boundary
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Main sequence binary fraction (57) and period
distribution (Duquennoy Mayor 1991)
How do we understand post-common envelope
stars? Population synthesis
These systems will widenbecause of mass-loss.
These systems will enter common envelope and
shift to shorter periods.
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What does ?CE depend on?
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How do we understand post-common envelope
stars? Population synthesis
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?CE in the literature
Yungelsons aCE is about 4 times smaller by
definition!!!
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Interpretation anti-correlation
This interpretation needs testing with hydro
codes, however Small companions take longer to
enter the envelope. If this time is Less than the
dynamical time of the star the star will react.
Nordhaus Blackman 2006
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Why do we care about aCE?

• Double Degenerates Supernovae Type Ia
• Close binary subdwarf
• Close-binary central stars of PN
• Cataclysmic Variables
• WD-main sequence binaries
• Low Mass X-ray binaries
• Several suspected merged stars
• also high mass binaries