We report the discovery of two millisecond pulsars in a search for radio pulsations at the positions of Fermi Large Area Telescope sources with no previously known counterparts , using the Nançay radio telescope .
The two millisecond pulsars , PSRs J2017+0603 and J2302+4442 , have rotational periods of 2.896 and 5.192 ms and are both in binary systems with low-eccentricity orbits and orbital periods of 2.2 and 125.9 days respectively , suggesting long recycling processes .
Gamma-ray pulsations were subsequently detected for both objects , indicating that they power the associated Fermi sources in which they were found .
The gamma-ray light curves and spectral properties are similar to those of previously-detected gamma-ray millisecond pulsars .
Detailed modeling of the observed radio and gamma-ray light curves shows that the gamma-ray emission seems to originate at high altitudes in their magnetospheres .
Additionally , X-ray observations revealed the presence of an X-ray source at the position of PSR J2302+4442 , consistent with thermal emission from a neutron star .
These discoveries along with the numerous detections of radio-loud millisecond pulsars in gamma rays suggest that many Fermi sources with no known counterpart could be unknown millisecond pulsars .