122728004
Search for Gravitational Waves from a nearby neutron star using barycentric resampling
Rapidly spinning neutron stars in our Galactic neighborhood are promising sources of quasi-monochromatic continuous gravitational waves observable by the current LIGO detectors. I describe a search done on the LIGO S5 data, looking for an isolated neutron star hypothesized to be at a distance of about 100 parsecs. This kind of search is computationally bound and is made possible by the implementation of barycentric resampling, which is described here as well. I also describe the work done at the Hanford LIGO site, while taking data for the Astrowatch program.
10187759
Searching for gravitational waves from Cassiopeia A with LIGO
We describe a search underway for periodic gravitational waves from the central compact object in the supernova remnant Cassiopeia A. The object is the youngest likely neutron star in the Galaxy. Its position is well known, but the object does not pulse in any electromagnetic radiation band and thus presents a challenge in searching the parameter space of frequency and frequency derivatives. We estimate that a fully coherent search can, with a reasonable amount of time on a computing cluster, achieve a sensitivity at which it is theoretically possible (though not likely) to observe a signal even with the initial LIGO noise spectrum. Cassiopeia A is only the second object after the Crab pulsar for which this is true. The search method described here can also obtain interesting results for similar objects with current LIGO sensitivity.
41307865
Implementation of barycentric resampling for continuous wave searches in gravitational wave data
We describe an efficient implementation of a coherent statistic for searches of continuous gravitational wave from neutron stars. The algorithm works by transforming the data taken by a gravitational wave detector from a moving Earth bound frame to one that sits at the Solar System barycenter. Many practical difficulties arise in the implementation of this algorithm, some of which have not been discussed previously. These difficulties include constraints of small computer memory, discreteness of the data, losses due to interpolation, and gaps in real data. This implementation is considerably more efficient than previous implementations of these kinds of searches on Laser Interferometer Gravitational Wave (LIGO) detector data. The speed-up factors range from 10, when applied to Einstein@Home, to about 2000 for targeted searches which integrate over months of data.
14253343
An imaging survey of a uniform sample of brightest cluster galaxies and intracluster light
We present deep, large-area B and r' imaging for a sample of 49 brightest cluster galaxies (BCGs). The clusters were selected by their X-ray luminosity and redshift to form two volume-limited samples, one with (z) ∼ 0.07 and the other at (z) ∼ 0.17. For each cluster, the data cover 41 × 41 arcmin 2 . We discuss our data-reduction techniques in detail, and show that we can reliably measure the surface brightness at the levels of μ B ∼ 29 and μ r' ∼ 28. For each galaxy, we present the B and r' images together with the surface brightness profile, B - r' colour, eccentricity and position angle as a function of radius. We investigate the distribution of positional offsets between the optical centroid of the BCG and the centre of the X-ray emission, and conclude that the mass profiles are cuspy, and do not have extended cores. We also introduce a method to objectively identify the transition from BCG to extended envelope of intracluster light, using the Petrosian index as a function of radius.