# Presentation: 014209

## The Astrophysics of Gravitational Wave Sources

- Conference Summary:
- Ground-Based Detectors
- (1-104 Hz)
- Kimberly New, LANL

**Notes:**
Thank scientific & administrative organizers of this conference,
& esp. Joan Centrella & Sandy Barnes for a stimulating & well-run
meeting.

## Detection & Data Analysis: LIGO & GEO’s science runsBrady & Mavalvala

- high sensitivity, large bandwidth, hours of coincident operation
- searches
-  NS/NS chirps, bursts, known pulsars, stochastic bkgd.
- techniques used
- science implications

**Notes:**
Let me begin with the subjects of detection & data analysis.
You just heard two talks about LIGO & GEO’s first science runs
These runs  had the highest sens., largest bandwidth, and largest hours of coincident operation of any to date
numb

## Detection & Data Analysis: Detectors in 2012Finn

- interferometers - sensitivity improvements
- <50 Hz:  improve seismic isolation
- active isolation
- multiple levels of suspension
- 50-200 Hz: mitigate thermal noise
- suspension system (increase mass, used fused silica ribbon)
- test masses (sapphire)
- >200 Hz: reduce shot noise
- increase laser power

**Notes:**
On the first day of the meeting, Sam Finn looked toward what detectors might be like in  a decade
large Youngs modulus, low thermal expansion

## Detection & Data Analysis: Detectors in 2012Finn

- resonant acoustic detectors
- current sensitivity 10-22 near 900 Hz  (1 Hz bandwidth)
- future
- spheres, spheres within spheres
- 100 Hz bandwidth near 1 KHz (with improved amplifiers)
*gravitational wave astronomy*
- NS/NS coalescence to 400 Mpc
- stellar BH/BH coalescence to z=0.5
- pulsars ( ~ 10-6 at 102 Hz)

**Notes:**
principal challenge: low noise amplifiers in cryogenic environment
spheres-all sky coverage
spheres within spheres - increase bandwidth
All this means that we’ll be seeing gw sources at larger & larger distances,
and thus be detecting them more frequently, and really be doing gw astronomy
regularly detecting coalescence

## Sources: BinariesSchutz, Centrella, Bulik, Heyl

- BH/BH Coalescence  (Centrella, Schutz)
- LIGO: stellar mass BH/BH binary final coalescence
- signal will contain astrophysically rich info: spins, strong field GR
- simulations of vacuum field eqns. scale w/ mass & spin
- evolve single BHs for 103M !
- binary BHs for 102M (~orbital period) !
- “Discovery Channel” simulation of merger (AEI)
- simulation of ringdown w/Lazarus perturbative code
- remaining numerical issues
- stability (formalism, gauge choices, boundary conditions)
- physical initial data
- waveform extraction

**Notes:**
codes still have issues with stability, boundary conditions, and initial data

“Discovery Channel” BH/BH merger simulation (AEI)
started 1/2 orbit prior to merger
followed through beginning of ringdown
need better initial data to constrain ISCO

## Sources: BinariesSchutz, Centrella, Bulik, Heyl

- chirp mass measurement could constrain binary evolution
- parameter studies with population synthesis code (Bulik, Kalogera)
- compact binary mass distribution: “fingerprints”
- most evolution input parameters could be constrained with ~100 chirp mass observations
- effects of r-mode instability on LMXBs  (Heyl)
- r-mode saturation
- detection with LIGO?
- EM signatures?

**Notes:**
Bulik:  input parameters incl., among others, kicks, mass transfer, Ics, BH formation, metallicity
mass distributions produced with this code are very sensitive to the details of high-mass stellar evolution - in that sense are “fingerprints”

## Sources: Intermediate-Mass Black HolesMushotzky, van der Marel, Miller

- observations suggest existence
- formation channels: Pop III stars, cluster interactions
- GWs
- 10-50 M, 10s of LIGO II detections per year
- > 100 M, frequency generally too low for LIGO (ringdown?)

**Notes:**
observations suggestive but not conclusive
10-50 Msun, old clusters
>100, young clusters & Pop III (might be able to see ringdown)

## Sources: CollapseMezzacappa, Fryer

- Core collapse supernovae
- precision modeling of macro & micro physics is the goal
- steps along the way indicate sensitivities                                    	(e.g., neutrino transport, EOS, general relativity)
- multi-D simulations with multi-frequency neutrino transport don’t yet yield explosions
- GW characteristics sensitive to EOS/GR                                     	(not as sensitive to neutrino transport)
- new 3D SPH simulations of  15 M stars  (Fryer & Warren)
- GWs from bar instability detectable with LIGO II (100 cycles, 10Mpc)
- GWs from proto-NS convection detectable for Galactic SNe

**Notes:**
GW emission likely more sensitive to effects of EOS/GR 
than neutrino transport (w/exception of convection about PNS-but
that’s likely to weak to detect anyway)

## Sources: CollapseMezzacappa, Fryer

- Pop III, first generation stars
- massive (no metallicity driven winds)
- SPH collapse simulation of 300 M rotating star (Fryer et al.)
- core rotating fast enough to develop dynamical bar instability
- high redshift puts GWs from bars & BH ringing out of LIGO II range
- fragmentation could be detectable with LIGO II (but does it occur?)

## Sources: GRBsMészáros, Norris

- GWs from GRBs
- long GRBs, strong association with collapse
- short GRBs, binary merger?
- GW and GRB emission polarized; observations with third generation detector could measure 1% polarization in a year  (Kobayashi & Mészáros)
- Nearby GRB/GW sources?  (Norris)
- class of nearby GRBs associated with Type Ic SNe?                 	(long pulses, long lags, soft spectra, subluminous)
- ex.: GRB 980425/ SN 1998bw (38 Mpc); GRB 030329 (680 Mpc)
- concentrated near Supergalactic Plane; observed asymmetries
- temporal separation of GRB and SNe? separate GW signatures?
- could see 4 per year with LIGO II  (50 Mpc, 100 cycle bar)

**Notes:**
GRBs could be associated with either SNe and/or binary coalescence

## Sources: unexpected

- dark matter?
- 30% of universe
- couple to gravitational radiation
- GW observations could determine if distribution is smooth

## In Summary

- What information can we provide along the way to self-consistent simulations?  (timing info, etc.)
- Observation Informs - Finn
- Is study of GWs from marginal sources worthwhile?
- have “guaranteed” sources, “luxury” of studying others
- often other drivers for study (SNe, GRBs, etc)
- today’s marginal source can become tomorrow’s observed source   	(galactic supernova)

**Notes:**
Physically complete simulations of many of these sources could be a ways down the road

Focus on what information can be provided along the way (time delay between neutrino and gw signals from SNe)

Observations could end up constraining theoretical & computational studies

Question was raised regarding worthiness of  study of sources whose prospects for detection are marginal

first, LIGO II should see binary coalescence, provides us with luxury of studying other types of sources
many classes of sources are studied for reasons besides GW emission
finally, good to continue investigations of this nature because today’s marginal source can turn into tomorrow’s observed source