Search of the Orion spur for continuous gravitational waves using a loosely coherent algorithm on data from LIGO interferometers

Abstract

We report results of a wideband search for periodic gravitational waves from isolated neutron starswithin the Orion spur towards both the inner and outer regions of our Galaxy. As gravitational wavesinteract very weakly with matter, the search is unimpeded by dust and concentrations of stars. One searchdisk (A) is 6.87° in diameter and centered on 20h10m54.71s þ 33°33025.2900, and the other (B) is 7.45° indiameter and centered on 8h35m20.61s − 46°49025.15100. We explored the frequency range of 50–1500 Hzand frequency derivative from 0 to −5 × 10−9 Hz=s. A multistage, loosely coherent search programallowed probing more deeply than before in these two regions, while increasing coherence length withevery stage. Rigorous follow-up parameters have winnowed the initial coincidence set to only 70candidates, to be examined manually. None of those 70 candidates proved to be consistent with an isolatedgravitational-wave emitter, and 95% confidence level upper limits were placed on continuous-wave strainamplitudes. Near 169 Hz we achieve our lowest 95% C.L. upper limit on the worst-case linearly polarizedstrain amplitude h0 of 6.3 × 10−25, while at the high end of our frequency range we achieve a worst-caseupper limit of 3.4 × 10−24 for all polarizations and sky locations.