Improved Upper Limits on Gravitational-wave Emission from NS 1987A in SNR 1987A

Abstract

We report on a new search for continuous gravitational waves from NS 1987A, the neutron star born in SN 1987A, using open data from Advanced LIGO and Virgo’s third observing run (O3). The search covered frequencies from 35–1050 Hz, more than 5 times the band of the only previous gravitational-wave search to constrain NS 1987A. Our search used an improved code and coherently integrated from 5.10 to 14.85 days depending on frequency. No astrophysical signals were detected. By expanding the frequency range and using O3 data, this search improved on strain upper limits from the previous search and was sensitive at the highest frequencies to ellipticities of 1.6 × 10−5 and r-mode amplitudes of 4.4 × 10−4, both an order of magnitude improvement over the previous search and both well within the range of theoretical predictions.

Assessing the Similarity of Continuous Gravitational-Wave Signals to Narrow Instrumental Artifacts

“…For instance, Ref. [40] uses the Cramér-von Mises statistic [41] to flag overpopulations of outliers within a few standard deviations of the mean; this is motivated by the fact that CW signals, on the other hand, tend to populate the very far end of a distribution's tail and thus have a negligible contribution to the Cramér-von Mises statistic.…”