Source simulation focus session at PennState

Pablo Laguna, PennState
pablo@astro.psu.edu

The Center for Gravitational Wave Physics at Penn State organized during October 28-30, 2002 a special "Focus Session" to address the topic of "Source Simulation and Gravitational Wave Data Analysis". The goal of this focus session was the interplay between source simulations and gravitational wave data analysis: how the results of source simulations can be used to design data analysis that extracts more information, or information more efficiently, from gravitational wave detector data. The program dealt with the concrete, as opposed to the abstract: on developing analysis that make use of calculations relating to specific characteristics of specific sources.

The Program consisted of the following talks:

*``Data Analysis in the Real World"* Sam Finn started his talk
reviewing the goals in source simulations and in data analysis. In
particular, he stressed the importance in carrying out source
simulations that identify the science reflected in the gravitational
waves. For the data analyst, he stressed the need for developing
techniques that make science stand-out and provide astrophysical
interpretation of observations. He also review the different classes
of sources: stochastic, periodic and bursts.

*``Linguistics of LISA Sources"* Scott Hughes presented an
overview of key LISA sources. In particular, he discussed questions
such as: What do we hope to learn from LISA sources? What is the
character of the signals these sources generate? He also addressed
the issue of how to design a strategy to measure LISA sources. He
pointed out that there is a big difference between detection and
measurement. He also discussed whether we can combine GW information
with other channels to maximize the astrophysical payoff.

*``Structure, Stability and Dynamical Behavior of Compact
Astrophysical Objects"* Joel Tohline presented a review of a meeting
that took place the weekend before the workshop. This meeting was
focused on two types of mechanisms in instabilities of compact
objects: Hydrodynamical instabilities such as bar-mode instabilities,
and GR driven instabilities (e.g. r-modes). Some of the issues
discussed in this meeting were: Mode identification, damping
mechanisms, expected maximum amplitude and duration, effects from GR
on mode character and likelihood of producing detectable GW signals.

*``Gravitational Waves from the Tidal Disruption of Neutron Stars
in Binaries"* Michele Vallisneri emphasized the importance of
investigating the correspondence between the EOS and mass-radius
function of NS. He discussed the possibility of using information from
NS tidal disruption in NS-BH binaries as a probe of the NS EOS.

*``Gamma Ray Bursts and Gravitational Waves"*
After a short review of GRBs, Shiho Kobayashi discussed
how the detection of counterparts of GRBs in GWs could
revolutionize the field. He pointed out that one
can use GRBs and afterglow observations
about the time and location of the event to perform a
cross-correlation and obtain information of the association
between GRBs and gravitational wave bursts.

*``Predicting the Gravitational Wave Signatures of Core Collapse
Supernovae: The Road Ahead"* Tony Mezzacappa presented the road
required in order to solve the core collapse supernovae problem,
including the gravitational radiation produced by these events. He
pointed out that waveforms will not be available any time soon. This
is an extremely difficult problem requiring a 3D-GR-Radiation-MHD code
plus state of the art nuclear and weak interaction physics. His talk
provided an overview of the current state of these simulations. In
particular, he showed simulations of accretion shock instabilities and
neutrino driven convection.

*``Gravitational Waves from Supernova Core Collapse: What Could
the Signal Tell Us"* Harald Dimmelmeier presented results from
simulations of supernova core collapse. He reviewed the physical
complexity and numerical difficulties involved in relativistic
simulations of rotational core collapse to a neutron star. He pointed
out that because of these complications it is necessary to introduce
several approximation. However, these approximations do not prevent
us from extracting new physics encoded in the waveforms. Their
simulations show that the remnants are more compact with higher
densities when compared with Newtonian results. In addition,
relativistic effects seem to increase the rotation rate, and in many
instances these effects could trigger tri-axial instabilities.

*``Low Frequency Gravitational Waves from the Galactic Halo"*
Shane Larson gave a talk reviewing first the MACHO search.
He then discussed the potential for LISA observations of
gravitational radiation from white dwarfs and black hole
MACHO binaries.

*``Binary Black Hole Coalescence in Galaxy Mergers"*
Steinn Sigurdsson stressed that although BBH coalescences
in galaxy merger could potentially have large S/N, the
rate of these events is likely to be low. He also addressed E&M and Spin
signatures as well as the possibility of observing stars bound to the BHs.

Other talks in the meeting included: ``Gravitational Wave Observations of Galactic Populations of Compact Binaries" by Matthew Benacquista, ``An Overview of 3D Black Hole Simulations" by Pablo Laguna, ``Bothrodesy: The Promise and Challenges of Extreme Mass Inspirals'' by Teviet Creighton, ``Probing the Equation of State of Neutron Stars with LIGO" by Fred Rasio

Links to presentations as PDF files can be found at http://cgwp.gravity.psu.edu/events/SrcSimDA/