We report the results of a directed search for continuous gravitational-wave emission in a broad frequency range (between 50 and 1000 Hz) from the central compact object of the supernova remnant Cassiopeia A (Cas A). The data comes from the sixth science run of LIGO and the search is performed on the volunteer distributed computing network Einstein@Home. We find no significant signal candidate, and set the most constraining upper limits to date on the gravitational-wave emission from Cas A, which beat the indirect age-based upper limit across the entire search range. At around 170 Hz (the most sensitive frequency range), we set 90% confidence upper limits on the gravitational wave amplitude h0 of ∼2.9×10−25, roughly twice as constraining as the upper limits from previous searches on Cas A. The upper limits can also be expressed as constraints on the ellipticity of Cas A; with a few reasonable assumptions, we show that at gravitational-wave frequencies greater than 300~Hz, we can exclude an ellipticity of ≳10−5.
@article{arxiv.1608.07589,
title = {An Einstein@home search for continuous gravitational waves from Cassiopeia A},
author = {Sylvia J. Zhu and Maria Alessandra Papa and Heinz-Bernd Eggenstein and Reinhard Prix and Karl Wette and Bruce Allen and Oliver Bock and David Keitel and Badri Krishnan and Bernd Machenschalk and Miroslav Shaltev and Xavier Siemens},
journal= {arXiv preprint arXiv:1608.07589},
year = {2016}
}