Theoretically Motivated Search and Detection of Non-thermal Pulsations from PSRs J1747-2958, J2021+3651, and J1826-1256

Based on a theoretical selection of pulsars as candidates for detection at X-ray energies, we present an analysis of archival X-ray observations performed with Chandra and XMM-Newton of PSR J1747–2958 (the pulsar in the "Mouse" nebula), PSR J2021+3651 (the pulsar in the "Dragonfly" nebula), and PSR J1826–1256. X-ray pulsations from PSR J1747–2958 and PSR J1826–1256 are detected for the first time, and a previously reported hint of an X-ray pulsation from PSR J2021+3651 is confirmed with a higher significance. We analyze these pulsars' spectra in regard to the theoretically predicted energy distribution, finding a remarkable agreement, and provide here a refined calculation of the model parameters taking into account the newly derived X-ray spectral data.