Discovery of two millisecond pulsars in Fermi sources with the Nancay Radio Telescope

TL;DR

This paper reports the discovery of two millisecond pulsars in Fermi sources using the Nancay Radio Telescope, confirming their gamma-ray emission and providing insights into their magnetospheric emission regions.

Contribution

First detection of millisecond pulsars in Fermi sources with radio and gamma-ray observations, revealing their emission properties and potential for uncovering many unknown pulsars.

Findings

Both pulsars are in low-eccentricity binary systems.

Gamma-ray pulsations confirmed their association with Fermi sources.

Gamma-ray emission likely originates at high altitudes in magnetospheres.

Abstract

We report the discovery of two millisecond pulsars in a search for radio pulsations at the positions of \emph{Fermi Large Area Telescope} sources with no previously known counterparts, using the Nan\c{c}ay 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 \emph{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 \emph{Fermi} sources with no known counterpart could be unknown millisecond pulsars.