First all-sky search for continuous gravitational waves from unknown sources in binary systems

Abstract

We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to ∼2; 254 h and a frequency-and period-dependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of projected semimajor axes of the orbit from ∼0.6 × 10 −3 ls to ∼6; 500 ls assuming the orbit of the binary is circular. While no plausible candidate gravitational wave events survive the pipeline, upper limits are set on the analyzed data. The most sensitive 95% confidence upper limit obtained on gravitational wave strain is 2.3 × 10 −24 at 217 Hz, assuming the source waves are circularly polarized. Although this search has been optimized for circular binary orbits, the upper limits obtained remain valid for orbital eccentricities as large as 0.9. In addition, upper limits are placed on continuous gravitational wave emission from the low-mass x-ray binary Scorpius X-1 between 20 Hz and 57.25 Hz.

Tuning into Scorpius X-1: adapting a continuous gravitational-wave search for a known binary system

“…TwoSpect is also, theoretically, highly robust against spin-wandering. This method has already been applied to real data [6], though not using the directed search in a fully templated mode. This experiment validates the programʼs robustness with respect to non-Gaussian data artifacts.…”

“…TwoSpect has already been described for the all-sky analysis [5,6]. Only a brief summary is given here of the elements common to the directed analysis, with details in the appendix.…”

“…The previously published all-sky search in a year of S6 data set an overall upper limit for circular polarization of´-2.3 10 24 at 217 Hz [6], set for an H1 amplitude spectral density of However, the all-sky paper included an opportunistic search for Sco X-1 on a narrow frequency range (20 to 57.25 Hz), setting a random polarization limit of´-2 10 23 at 57 Hz in an L1 amplitude spectral density´--1.8 10 Hz 22 1 2 , a depth of 9 Hz -1 2 . This opportunistic search used 1800-s SFTs; longer SFT durations increase theoretical sensitivity.…”

“…This method can apply to continuouswave (CW) GWs of unknown frequencies from neutron stars in binary systems, with unknown sky locations, orbital periods, or projected semi-major axes. It was used in a priori all-sky search for CWs from unknown sources with data from LIGO Science Run 6 and Virgo Science Runs 2 and 3 [6]. This paper describes analysis modifications, when sky location and orbital period are known, to run a directed search.…”

Search for continuous gravitational waves from neutron stars in globular cluster NGC 6544

“…These are very computationally costly, searching over wide frequency bands and covering large ranges of spin-down parameters [8][9][10][11][12][13][14][15][16][17]. The latest of these have incorporated new techniques to cover possible binary parameters as well [18]. Recent all-sky searches have set direct upper limits close to indirect upper limits derived from galactic neutron-star population simulations [19].…”