Deep Einstein@Home search for Continuous Gravitational Waves from the Central Compact Objects in the Supernova Remnants Cas A, Vela Jr. and G347.3-0.5 using LIGO public O3 and O4a data

We perform a search for continuous nearly monochromatic gravitational waves from the central compact objects associated with the supernova remnants (SNRs) Cas A, Vela Jr. and G347.3 using LIGO O3 public data.

The searches for all three targets have the board frequency range from 20 and 1500 Hz. The search is deployed on the volunteer computing project Einstein@Home for six monthes, with thousands of participants donating compute cycles to make this endeavour possible. After the search is done, we perform multi-stages sub-threshold follow-up searches for over 45 million most promising waveforms out of 1e19 of the original search.

It is to date the most sensitive search for continuous gravitational waves from these three SNRs and the widest frequency spindown range searches as well.

Although we do not find any significant signals, we are able to set upper limits on the gravitational wave strain amplitude $h_0$ for the three SNRs. From all three SNRs, we set the most stringent upper limit on $h_0$ to date, and based on this, we set the most stringent upper limit on the neutron star's ellipticity and the the r-mode instability anplitude. We also first time in history constrain the spin of these three neutron stars using our observational upper limits results in the case of the neutron stars' crusts are anisotropic.