Searches for continuous gravitational waves from Scorpius X-1 and XTE J1751-305 in LIGO's sixth science run

Abstract

Scorpius X-1 (Sco X-1) and X-ray transient (XTE) J1751-305 are Low-Mass X-ray Binaries (LMXBs) that may emit continuous gravitational waves detectable in the band of ground-based interferometric observatories. Neutron stars in LMXBs could reach a torque-balance steady-state equilibrium in which angular momentum addition from infalling matter from the binary companion is balanced by angular momentum loss, conceivably due to gravitational-wave emission. Torque-balance predicts a scale for detectable gravitational-wave strain based on observed X-ray flux. This paper describes a search for Sco X-1 and XTE J1751-305 in LIGO Science Run 6 data using the TwoSpect algorithm, based on searching for orbital modulations in the frequency domain. While no detections are claimed, upper limits on continuous gravitational-wave emission from Sco X-1 are obtained, spanning gravitational-wave frequencies from 40 to 2040 Hz and projected semi-major axes from 0.90 to 1.98 light-seconds. These upper limits are injection validated, equal any previous set in initial LIGO data, and extend over a broader parameter range. At optimal strain sensitivity, achieved at 165 Hz, the 95% confidence level random-polarization upper limit on dimensionless strain $h_0$ is approximately $1.8\times 10^{-24}$. Closest approach to the torque-balance limit, within a factor of 27, is also at 165 Hz. These are the first upper limits known to date on $r$-mode emission from this XTE source. Upper limits are set in particular narrow frequency bands of interest for J1751-305. The TwoSpect method will be used in upcoming searches of Advanced LIGO and Virgo data.

14 pages, 6 figures

References in corpus (12)

• Detecting gravitational wave emission from the known accreting neutron stars
• Calibration of the LIGO Gravitational Wave Detectors in the Fifth Science Run
• Einstein@Home all-sky search for periodic gravitational waves in LIGO S5 data
• Postprocessing methods used in the search for continuous gravitational-wave signals from the Galactic Center
• The cross-correlation search for periodic gravitational waves
• First all-sky search for continuous gravitational waves from unknown sources in binary systems
• Directed searches for continuous gravitational waves from binary systems: parameter-space metrics and optimal Scorpius X-1 sensitivity
• Implications of an r-mode in XTE J1751-305: Mass, radius and spin evolution
• Gravitational waves from Sco X-1: A comparison of search methods and prospects for detection with advanced detectors
• A directed search for gravitational waves from Scorpius X-1 with initial LIGO
• Excitation of a nonradial mode in a millisecond X-ray pulsar XTE J1751-305
• Model-Based Cross-Correlation Search for Gravitational Waves from Scorpius X-1

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• Ultra-compact X-ray binaries as dual-line gravitational-wave sources
• Model-based cross-correlation search for gravitational waves from the low-mass X-ray binary Scorpius X-1 in LIGO O3 data
• Hidden Markov model tracking of continuous gravitational waves from a neutron star with wandering spin. III. Rotational phase tracking
• Search for Gravitational Waves from Scorpius X-1 in LIGO O3 Data With Corrected Orbital Ephemeris
• Eclipses of continuous gravitational waves as a probe of stellar structure
• Implementation of a new weave-based search pipeline for continuous gravitational waves from known binary systems
• Deep searches for X-ray pulsations from Scorpius X-1 and Cygnus X-2 in support of continuous gravitational wave searches