Searches for Gravitational Waves from Known Pulsars at Two Harmonics in the Second and Third LIGOVirgo Observing Runs
Abstract
We present a targeted search for continuous gravitational waves (GWs) from 236 pulsars using data from the third observing run of LIGO and Virgo (O3) combined with data from the second observing run (O2). Searches were for emission from the l = m = 2 mass quadrupole mode with a frequency at only twice the pulsar rotation frequency (single harmonic) and the l = 2, m = 1, 2 modes with a frequency of both once and twice the rotation frequency (dual harmonic). No evidence of GWs was found, so we present 95% credible upper limits on the strain amplitudes h _{0} for the singleharmonic search along with limits on the pulsars' mass quadrupole moments Q _{22} and ellipticities ɛ. Of the pulsars studied, 23 have strain amplitudes that are lower than the limits calculated from their electromagnetically measured spindown rates. These pulsars include the millisecond pulsars J0437‑4715 and J0711‑6830, which have spindown ratios of 0.87 and 0.57, respectively. For nine pulsars, their spindown limits have been surpassed for the first time. For the Crab and Vela pulsars, our limits are factors of ∼100 and ∼20 more constraining than their spindown limits, respectively. For the dualharmonic searches, new limits are placed on the strain amplitudes C _{21} and C _{22}. For 23 pulsars, we also present limits on the emission amplitude assuming dipole radiation as predicted by BransDicke theory.
 Publication:

The Astrophysical Journal
 Pub Date:
 August 2022
 DOI:
 10.3847/15384357/ac6acf
 arXiv:
 arXiv:2111.13106
 Bibcode:
 2022ApJ...935....1A
 Keywords:

 Gravitational waves;
 Gravitational wave sources;
 Pulsars;
 Neutron stars;
 Astrophysics  High Energy Astrophysical Phenomena;
 General Relativity and Quantum Cosmology
 EPrint:
 37 pages