Ability of LISA to detect a gravitational-wave background of cosmological origin: The cosmic string case

Abstract

We investigate the ability of the Laser Interferometer Space Antenna (LISA) to detect a stochastic gravitational-wave background (GWB) produced by cosmic strings, and to subsequently estimate the string tension Gμ in the presence of instrument noise, an astrophysical background from compact binaries, and the galactic foreground from white dwarf binaries. Fisher Information and Markov Chain Monte Carlo methods provide estimates of the LISA noise and the parameters for the different signal sources. We demonstrate the importance of including the galactic foreground as well as the astrophysical background for LISA to detect a cosmic string produced GWB and estimate the string tension. Considering the expected astrophysical background and a galactic foreground, a cosmic string tension in the Gμ ≈ 10 −16 to Gμ ≈ 10 −15 range or bigger could be measured by LISA, with the galactic foreground affecting this limit more than the astrophysical background. The parameter estimation methods presented here can be applied to other cosmological backgrounds in the LISA observation band.

Stochastic Gravitational-Wave Backgrounds: Current Detection Efforts and Future Prospects

“…In fact, component separation will be a major challenge for LISA data analysis, as a variety of signals will contribute to the same frequency band and overlap in time [360]. In the case of stochastic backgrounds, as detailed in Section 3, LISA will be sensitive to an anisotropic galactic white dwarf binary background which traces the shape of the Milky Way, a mostly isotropic background of either primordial or stellar-origin black hole and neutron star binaries [361], and also potentially other primordial backgrounds, such as those arising from inflation [93], first-order phase transitions [55,362], and cosmic strings [53,363], all of which may be either isotropic or anisotropic. Galactic binaries will by far dominate the measurement, and in fact several approaches have been proposed towards component separation, relying on characteristic, observable differences of each component such as their spectral shape [148,364], or their distribution on the sky, as seen in [193,194].…”

Gravitational Waves: The Theorist’s Swiss Knife

“…However, to obtain these limits, only the LISA noise was taken into account. Considering the cosmic string GWB in the presence of a compact binary produced astrophysical background and a galactic foreground, in addition to the LISA noise, it was shown [52] that, with four years of data, LISA will be able to measure a cosmic string tension Gµ ≈ 10 −16 (for the model [53]) to Gµ ≈ 10 −15 (for the models [44,48,49]) or bigger; the galactic foreground affecting the Gµ limit more than the astrophysical background.…”

Stochastic Gravitational-Wave Backgrounds: Current Detection Efforts and Future Prospects

“…In fact, component separation will be a major challenge for LISA data analysis, as a variety of signals will contribute to the same frequency band and overlap in time [361]. In the case of stochastic backgrounds, as detailed in Section 3, LISA will be sensitive to an anisotropic galactic white dwarf binary background which traces the shape of the Milky Way, a mostly isotropic background of either primordial or stellar-origin black hole and neutron star binaries [362], and also potentially other primordial backgrounds, such as those arising from inflation [94], first-order phase transitions [55,363], and cosmic strings [53,364], all of which may be either isotropic or anisotropic. Galactic binaries will by far dominate the measurement, and in fact several approaches have been proposed towards component separation, relying on characteristic, observable differences of each component such as their spectral shape [149,365], or their distribution on the sky, as seen in [194,195].…”