Gravitational Wave Searches for Post-Merger Remnants of GW170817 and GW190425

We present the results of two searches for gravitational waves from the post-merger remnants of the binary neutron star coalescence events GW170817 and GW190425. The searches are fully coherent over 1800 s of data from the 2nd (for GW170817) and 3rd (for GW190425) observing runs of the LIGO and Virgo observatories. The searches compute the matched filter ℱ-statistic, and use a piecewise model of the rapidly changing frequency evolution appropriate for young neutron stars. No detection is claimed. The peak root-sum-squared strain upper limit at 50% detection probability (h_rss^50%) of both searches occurs at 1700 Hz and is estimated at 1.64 × 10^-22 Hz^-1/2 for GW170817, and 1.0 × 10^-22 Hz^-1/2 for GW190425. This is the first gravitational wave search for a neutron star remnant of GW190425.