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キーワード:
General Relativity and Quantum Cosmology, gr-qc, Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE, Astrophysics, Instrumentation and Methods for Astrophysics, astro-ph.IM
要旨:
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 $h_0$ of $\sim\!\!~2.9\times 10^{-25}$, 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 $\gtrsim\!\!~10^{-5}$.
