Pulsar searches of Fermi unassociated sources with the Effelsberg telescope

TL;DR

This paper reports the discovery of a millisecond pulsar in a binary system through targeted radio searches of Fermi gamma-ray sources, confirming its gamma-ray emission and analyzing its spectral properties.

Contribution

It presents the first pulsar discovery from a targeted Effelsberg radio survey of Fermi unassociated sources and confirms its gamma-ray counterpart with detailed timing and spectral analysis.

Findings

Discovered millisecond pulsar J1745+1017 in a binary system.

Detected gamma-ray emission phase-aligned with radio pulsar.

Identified reasons for low discovery yield in the survey.

Abstract

Using the 100-m Effelsberg radio telescope operating at 1.36 GHz, we have performed a targeted radio pulsar survey of 289 unassociated gamma-ray sources discovered by the Large Area Telescope (LAT) aboard the Fermi satellite and published in the 1FGL catalogue (Abdo et al., 2010). This survey resulted in the discovery of millisecond pulsar J1745+1017, which resides in a short-period binary system with a low-mass companion, Mmin ~ 0.0137 Msun, indicative of `Black Widow' type systems. A two-year timing campaign has produced a refined radio ephemeris, accurate enough to allow for phase-folding of the LAT photons, resulting in the detection of a dual-peaked gamma-ray light-curve, proving that PSR J1745+1017 is the source responsible for the gamma-ray emission seen in 1FGL J1745.5 + 1018 (2FGL J1745.6+1015; Nolan et al., 2012). We find the gamma-ray spectrum of PSR J1745+1017 to be well modelled by an exponentially-cut-off power law with cut-off energy 3.2 GeV and photon index 1.6. The observed sources are known to contain a further 10 newly discovered pulsars which were undetected in this survey. Our radio observations of these sources are discussed and in all cases limiting flux densities are calculated. The reasons behind the seemingly low yield of discoveries are also discussed.