Kavli Affiliate: Lijing Shao
| First 5 Authors: Garvin Yim, Yong Gao, Yacheng Kang, Lijing Shao, Renxin Xu
| Summary:
Gravitational waves from isolated sources have eluded detection so far. The
upper limit of long-lasting continuous gravitational wave emission can now
probe physically-motivated models with the most optimistic being strongly
constrained. Naturally, one might want to relax the assumption of the
gravitational wave being quasi-infinite in duration, leading to the idea of
transient continuous gravitational waves. In this paper, we outline how to get
transient continuous waves from magnetars (or strongly-magnetised neutron
stars) that exhibit glitches and/or antiglitches and apply the model to
magnetar SGR J1935+2154. The toy model hypothesizes that at a glitch or
antiglitch, mass is ejected from the magnetar but becomes trapped on its
outward journey through the magnetosphere. Depending on the height of the
trapped ejecta and the magnetic inclination angle, we are able to reproduce
both glitches and antiglitches from simple angular momentum arguments. The
trapped ejecta causes the magnetar to precess leading to gravitational wave
emission at once and twice the magnetar’s spin frequency, for a duration equal
to however long the ejecta is trapped for. We find that the gravitational waves
are more detectable when the magnetar is: closer, rotating faster, or has
larger glitches/antiglitches. The detectability also improves when the ejecta
height and magnetic inclination angle have values near their critical values,
though this requires more mass to be ejected to remain consistent with the
observed glitch/antiglitch. We find it unlikely that gravitational waves will
be detected from SGR J1935+2154 when using the trapped ejecta model.
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