SLIDE 1
Gravitational Waves and Stellar Populations
Learning from Detection WHAT ? HOW ?
High - frequency Low - frequency > Compact Object Inspiral > Compact Object Inspiral > Compact Object Formation > NS as Periodic sources
SLIDE 2 Populations of Double Compact Objects
Measured properties include: event rates masses of compact objects What we can learn about the astrophysics of stellar populations depends on whether a whole population of inspiraling double compact objects
- r just a few inspiral events have been detected
GW observational selection effects and biases must be considered quantitatively
SLIDE 3 Populations of Double Compact Objects
- A. Event Rate measurements
> even a few events can be used (we know that !)
> if more than one DCO types are detected relative inspiral rates can be derived for different DCO types (NS-NS, BH-NS, BH-BH)
> comparison with theoretical rate predictions can constrain the systematic uncertainties in binary evolution models
(e.g., stellar winds, details of mass transfer, SN kicks)
> comparison to estimates of GRB rates
SLIDE 4 Populations of Double Compact Objects
whole population detected: model fitting a few events detected: model exclusion
(possibly with BH-BH ... )
with theoretical models as priors either way: constraints on DCO formation models
SLIDE 5
first SN second SN
Models of Mass Distributions
standard model inefficient CE ejection weak stellar winds
Populations of Double Compact Objects
For example:
Belczynski et al. 2001
Constraints on astrophysical models of DCO formation
and on specifics of stellar evolutionary phases
SLIDE 6 Populations of Double Compact Objects
NS EOS Constraints:
if inspiral signal shows evidence for the presence of NS e.g., merger signal characteristic of a NS (Faber & Rasio
2001)
and both of the measured masses exceed 1.5Mo or 2.0Mo if signal of NS disruption by a BH is detected: > NS radius measurement is possible (Vallisneri 2000) Note: fractional errors of ~ 10% needed for firm conclusions
SLIDE 7
Populations of Double Compact Objects
Some Observational Biases:
detection bias against massive binaries (BH-NS & BH-BH) > affects event rate estimates and relative inspiral rates > even without any corrections: treat inferred rates as limits and still constrain models detection bias against strongly precessing binaries > preferentially affects high-mass ratios (BH-NS) > if `mock' precessing templates are used, is parameter estimation possible ??? parameter estimation bias for sources at high redshift > preferentially affects most massive binaries > correction crucially depends on EM counterparts and redshift measurements
How can we correct for these ?
SLIDE 8
Burst Sources
Detection even with advanced detectors is uncertain given the current physical understanding (e.g., Fryer et al. 2001)
but bursts may very well be detected either because our
expectations do not represent reality or because there are sources we have not considered. In that case ... Can we identify the origin of detected bursts ?
> BH ring-down may be the easiest (gives us: mass & spin) > EM counterparts may prove crucial or even necessary! e.g., association with a GRB or SN
What if none of the above materializes ? > a large sample becomes crucial
(for studies of space distributions, log N-log S studies)
SLIDE 9 Burst Sources
What can BH ring-down signals tell us ?
BH mass: measurements in excess of 15-20Mo will challenge stellar evolution models a large sample and EM counterparts will allow examination of differences between single or binary progenitors BH spin: constraints on angular momentum content
Bias: against low-mass and fast-spinning BH (high ring-down frequencies) association with SN: unique confirmation of BH formation through fallback
SLIDE 10 Periodic Sources
Non-axisymmetric PSRs
Detection and measurement of the degree of asymmetry constraints on NS EOS and theory of vortex pinning
Free Precessing PSRs
Two observed PSRs are claimed to be free-precessing (PSR 1828-11 Lyne et al. 2000 PSR 1642-03 Shabanova et al. 2001) Signal detection can allow the measurement of > misalignment of body and rotation axes > rotation axis relative to line-of-sight combined with radio observations will allow tests of pulsar beaming models
Accreting NS
Detection could provide unique confirmation for the role
- f GW waves in determining NS spins in LMXBs
SLIDE 11
GW Source Locations
(with multiple detectors)
very important: > large number of detections for studies of anisotropicities in space distributions > identification of EM counterparts
for
association with known sources for association with host galaxies and studies of correlations with galaxy types and relative positions accuracy of localization and distance measurements ?
SLIDE 12
Binary Compact Objects > detection of different DCO types > mass measurement errors down to ~10% > identify NS signature in merger signals correct for > spin effects and precession > bias against massive binaries
Burst Sources
> localization > EM counterparts
SLIDE 13
LISA and Double Compact Objects
Galactic WD-WD binaries:
continuous background up to 3-4mHz individual sources at higher freq. Note: model predictions appear remarkably robust ! (moderately sensitive to mass-ratios of primordial binaries) implication: weak model constraints ... What can we learn ? from background: WD-WD merger rate from individual detections (~103): WD-WD Galactic space distribution (impossible from EM observations) for a few of them: prediction for a Type Ia SN event ???
SLIDE 14
LISA and Double Compact Objects
Specific Galactic binaries: With known positions
can CVs and LMXBs be detected below the `WD-WD noise' ??? if yes: reliable orbital period measurements (difficult in EM ... )
