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Title: Precision ephemerides for gravitational-wave searches. I. Sco X-1

Rapidly rotating neutron stars are the only candidates for persistent high-frequency gravitational wave emission, for which a targeted search can be performed based on the spin period measured from electromagnetic (e.g., radio and X-ray) observations. The principal factor determining the sensitivity of such searches is the measurement precision of the physical parameters of the system. Neutron stars in X-ray binaries present additional computational demands for searches due to the uncertainty in the binary parameters. We present the results of a pilot study with the goal of improving the measurement precision of binary orbital parameters for candidate gravitational wave sources. We observed the optical counterpart of Sco X-1 in 2011 June with the William Herschel Telescope and also made use of Very Large Telescope observations in 2011 to provide an additional epoch of radial-velocity measurements to earlier measurements in 1999. From a circular orbit fit to the combined data set, we obtained an improvement of a factor of 2 in the orbital period precision and a factor of 2.5 in the epoch of inferior conjunction T {sub 0}. While the new orbital period is consistent with the previous value of Gottlieb et al., the new T {sub 0} (and the amplitudemore » of variation of the Bowen line velocities) exhibited a significant shift, which we attribute to variations in the emission geometry with epoch. We propagate the uncertainties on these parameters through to the expected Advanced LIGO-Virgo detector network observation epochs and quantify the improvement obtained with additional optical observations.« less
Authors:
;  [1] ; ;  [2] ; ;  [3]
  1. Monash Centre for Astrophysics, Monash University, VIC 3800 (Australia)
  2. Department of Physics, Astronomy and Astrophysics Group, University of Warwick, Coventry CV4 7AL (United Kingdom)
  3. Instituto de Astrofísica, E-38205, La Laguna, Tenerife (Spain)
Publication Date:
OSTI Identifier:
22348186
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 781; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; AMPLITUDES; BINARY STARS; COSMIC GAMMA SOURCES; DATA; EMISSION; GRAVITATIONAL WAVES; NEUTRON STARS; NEUTRONS; ORBITS; RADIAL VELOCITY; SENSITIVITY; SPIN; TELESCOPES; VARIATIONS; X RADIATION