Understanding the AM CVn population: The implications of improved - - PowerPoint PPT Presentation
Understanding the AM CVn population: The implications of improved theory for WD channel systems Christopher Deloye (Northwestern University) collaborators: Ron Taam, Gijs Roelofs, Gijs Nelemans, Lev Yungelson Image Credit: T. Strohmayer & D.
collaborators: Ron Taam, Gijs Roelofs, Gijs Nelemans, Lev Yungelson
Image Credit: T. Strohmayer & D. Berry
AM CVn noun, proper (slang, or at best, archaic jargon)
enaticorum peculiar in its marked absence of hydrogen, very short period of variability, and very blue color. AM CVn binary (or star, variable) noun (even worse archaic jargon)
classical cataclysmic variables (roughly 70 minutes) during its most recent episode of continuous mass transfer. The second condition implies that the donor has processed at least a significant fraction, if not all, of its core H into He (and possibly further into C/O in some hypothetical cases) before the system’s global orbital period minimum is reached. Three distinct formation channels are commonly discussed for AM CVn binaries, one of which can be connected to the classical cataclysmic variable population via a continuous variation of a single-parameter.
( Podsiadlowski et al. 2003)
(Nelemans et al. 2001)
(Nelemans et al. 2001)
evolution.
period.
period.
(Y ungelson 2005)
CV channel He-star channel WD channel
angular momentum losses.
contact.
for a time post-contact.
transfer.
Deloye et al. 2005) assumed
angular momentum losses.
contact.
for a time post-contact.
transfer.
Deloye et al. 2005) assumed
angular momentum losses.
contact.
for a time post-contact.
transfer.
Deloye et al. 2005) assumed
Start of Mass T ransfer
angular momentum losses.
contact.
for a time post-contact.
transfer.
Deloye et al. 2005) assumed
Start of Mass T ransfer
assumptions about donor’s:
degeneracy-dependent donor contraction (non-isentropic
(adiabatic donor expansion).
thermal evolution).
Relevant Time Scales:
τM ≈ m ˙ M τth ≈ m cP Tdm L
(m = M2 − m)
(Deloye et al. 2007)
evolution properties during AM CVn phase.
determined by donor’s initial entropy:
distribution of initial donor entropy within population).
(Deloye et al. 2007)
evolution properties during AM CVn phase.
determined by donor’s initial entropy:
distribution of initial donor entropy within population).
Evolutionary Stages
(Deloye et al. 2007)
evolution properties during AM CVn phase.
determined by donor’s initial entropy:
distribution of initial donor entropy within population).
Evolutionary Stages
(Deloye et al. 2007)
evolution properties during AM CVn phase.
determined by donor’s initial entropy:
distribution of initial donor entropy within population).
Evolutionary Stages
(Deloye et al. 2007)
tidal heating).
modeling inputs.
towards zero-temperature M2-R2 relation.
(Based on Nelemans et al. 2004 & Deloye et al. 2007)
tidal heating).
modeling inputs.
towards zero-temperature M2-R2 relation.
Lower limit insensitive to distribution of post-CE donor states.
(Based on Nelemans et al. 2004 & Deloye et al. 2007)
Cooling Starts
Most Observed Systems are ≲ 1 Gyr post-contact. Cooling Starts
(Marsh et al. 2006, Roelofs et al. 2007) (He-star models: Y ungelson 2008)
hot!!!
(Marsh et al. 2006, Roelofs et al. 2007) (He-star models: Y ungelson 2008)
hot!!!
with WD channel origin.
(Marsh et al. 2006, Roelofs et al. 2007) (He-star models: Y ungelson 2008)
hot!!!
with WD channel origin.
(Marsh et al. 2006, Roelofs et al. 2007) (He-star models: Y ungelson 2008)
hot!!!
with WD channel origin.
(Marsh et al. 2006, Roelofs et al. 2007) (He-star models: Y ungelson 2008)
hot!!!
with WD channel origin.
with hot donors preferentially survive contact)?
(Marsh et al. 2006, Roelofs et al. 2007) (He-star models: Y ungelson 2008)
hot!!!
with WD channel origin.
with hot donors preferentially survive contact)?
tidal heating at short orbital periods) ?
(Marsh et al. 2006, Roelofs et al. 2007) (He-star models: Y ungelson 2008)
hot!!!
with WD channel origin.
with hot donors preferentially survive contact)?
tidal heating at short orbital periods) ?
abundances consistent with this channel dominating AM CVn production (Lev and Gijs N. working on this)?
(Marsh et al. 2006, Roelofs et al. 2007) (He-star models: Y ungelson 2008)
(Marsh & Steeghs 2002)
Accretor spin-up provides a sink for
to the instability of mass transfer. Stability Criteria: ⇒ q < 5 6 + ξ2 2 −
(in absence of efficient tidal torques.)
(Marsh et al. 2004)
rh : parameterizes J lost in accreted
mattter.
ξ2 = d ln R2 d ln M2 q ≡ M2 M1
(Marsh & Steeghs 2002)
Accretor spin-up provides a sink for
to the instability of mass transfer. Stability Criteria: ⇒ q < 5 6 + ξ2 2 −
(in absence of efficient tidal torques.)
(Marsh et al. 2004)
rh : parameterizes J lost in accreted
mattter.
ξ2 = d ln R2 d ln M2 q ≡ M2 M1
For fully degenerate donors, DI accretion produces unstable mass transfer in vast majority of WD Channel systems (in absence of efficient tidal coupling).
(Nelemans et al. 2001, Marsh et al 2004)
minimum ξ2.
preferentially for
donor (Gijs R. working
with ≲10% required by
hottest observed donors. (τs → ∞)
(Unconditionally Stable)
log(ψc,i) = 1.1, 1.5, 2.0, , 3.0
M1,i = 0.3M M1,i = 0.4M M2,i = 0.2M
evolution while donor contracts.
Schematic Only!
evolution while donor contracts.
Schematic Only!
Prior Expectations
evolution while donor contracts.
Schematic Only!
Prior Expectations Peak height/width: donor entropy distribution
evolution while donor contracts.
Schematic Only!
Prior Expectations Peak center: system mass distribution Peak height/width: donor entropy distribution
evolution while donor contracts.
plane surveys??) could be extremely relevant/important here.
independent determination of distribution of above properties.
Schematic Only!
Prior Expectations Peak center: system mass distribution Peak height/width: donor entropy distribution
minima provides information on
Schematic Only!
minima provides information on
Schematic Only!
Prior Expectations
minima provides information on
Schematic Only!
Porb-min peak of surviving systems
minima provides information on
Schematic Only!
Loss of cold-donor systems affects slope.
minima provides information on
Schematic Only!
Pre-contact entropy higher than currently expected (tidal heating?).
minima provides information on
Schematic Only!
minima provides information on
(still) in progress (with my apologies to Gijs N. and Lev). Schematic Only!
minima provides information on
(still) in progress (with my apologies to Gijs N. and Lev).
cold-donor systems filtered-out at contact?
pre-contact system evolution.
answer to this question.
Schematic Only!
uncertain
uncertain
uncertain
metrics:
contact.
populations.
detailed models, and careful looks at interplay of multiple physics near contact.