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/