3 research outputs found
Advanced localization of massive black hole coalescences with LISA
The coalescence of massive black holes is one of the primary sources of
gravitational waves (GWs) for LISA. Measurements of the GWs can localize the
source on the sky to an ellipse with a major axis of a few tens of arcminutes
to a few degrees, depending on source redshift, and a minor axis which is 2--4
times smaller. The distance (and thus an approximate redshift) can be
determined to better than a per cent for the closest sources we consider,
although weak lensing degrades this performance. It will be of great interest
to search this three-dimensional `pixel' for an electromagnetic counterpart to
the GW event. The presence of a counterpart allows unique studies which combine
electromagnetic and GW information, especially if the counterpart is found
prior to final merger of the holes. To understand the feasibility of early
counterpart detection, we calculate the evolution of the GW pixel with time. We
find that the greatest improvement in pixel size occurs in the final day before
merger, when spin precession effects are maximal. The source can be localized
to within 10 square degrees as early as a month before merger at ; for
higher redshifts, this accuracy is only possible in the last few days.Comment: 11 pages, 4 figures, version published in Classical and Quantum
Gravity (special issue for proceedings of 7th International LISA Symposium
Massive Black Hole Binary Inspirals: Results from the LISA Parameter Estimation Taskforce
The LISA Parameter Estimation (LISAPE) Taskforce was formed in September 2007
to provide the LISA Project with vetted codes, source distribution models, and
results related to parameter estimation. The Taskforce's goal is to be able to
quickly calculate the impact of any mission design changes on LISA's science
capabilities, based on reasonable estimates of the distribution of
astrophysical sources in the universe. This paper describes our Taskforce's
work on massive black-hole binaries (MBHBs). Given present uncertainties in the
formation history of MBHBs, we adopt four different population models, based on
(i) whether the initial black-hole seeds are small or large, and (ii) whether
accretion is efficient or inefficient at spinning up the holes. We compare four
largely independent codes for calculating LISA's parameter-estimation
capabilities. All codes are based on the Fisher-matrix approximation, but in
the past they used somewhat different signal models, source parametrizations
and noise curves. We show that once these differences are removed, the four
codes give results in extremely close agreement with each other. Using a code
that includes both spin precession and higher harmonics in the
gravitational-wave signal, we carry out Monte Carlo simulations and determine
the number of events that can be detected and accurately localized in our four
population models.Comment: 14 pages, 2 figures, 5 tables, minor changes to match version to be
published in the proceedings of the 7th LISA Symposium. For more information
see the Taskforce's wiki at http://www.tapir.caltech.edu/dokuwiki/lisape:hom