First searches for gravitational waves from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>r</mml:mi></mml:math>-modes of the Crab pulsar
Binod Rajbhandari, B. J. Owen, Santiago Caride, Ra Inta
Abstract
We present the first searches for gravitational waves from $r$-modes of the Crab pulsar, coherently and separately integrating data from three stretches of the first two observing runs of Advanced LIGO using the $\mathcal{F}$-statistic. The second run was divided in two by a glitch of the pulsar roughly halfway through. The frequencies and derivatives searched were based on radio measurements of the pulsar's spin-down parameters as described in Caride et al., [Phys. Rev. D 100, 064013 (2019)]. We did not find any evidence of gravitational waves. Our best 90% confidence upper limits on gravitational wave intrinsic strain were $1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}25}$ for the first run, $1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}25}$ for the first stretch of the second run, and $1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}25}$ for the second stretch of the second run. These are the first upper limits on gravitational waves from $r$-modes of a known pulsar to beat its spin-down limit, and they do so by more than an order of magnitude in amplitude or two orders of magnitude in luminosity.