A multiwavelength study on the high-energy behaviour of Fermi/LAT pulsars

TL;DR

This study analyzes the X-ray and gamma-ray emissions of Fermi/LAT pulsars, revealing significant variability in flux ratios likely due to different geometrical configurations and differences between radio-loud and radio-quiet pulsars.

Contribution

It provides a comprehensive multiwavelength analysis of Fermi pulsars, highlighting the diversity in flux ratios and geometrical configurations, and compares properties of radio-loud and radio-quiet pulsars.

Findings

Fermi pulsars exhibit a 3-decade spread in gamma/X-ray flux ratios.

Radio-quiet pulsars tend to have higher gamma/X-ray flux ratios.

Radio-quiet pulsars show less scatter, indicating more constrained geometries.

Abstract

Using archival as well as freshly acquired data, we assess the X-ray behaviour of the Fermi/LAT gamma-ray pulsars listed in the First Fermi source catalog. After revisiting the relationships between the pulsars' rotational energy losses and their X and gamma-ray luminosities, we focus on the distance-indipendent gamma to X-ray flux ratios. When plotting our Fgamma/Fx values as a function of the pulsars' rotational energy losses, one immediately sees that pulsars with similar energetics have Fgamma/Fx spanning 3 decades. Such spread, most probably stemming from vastly different geometrical configurations of the X and gamma-ray emitting regions, defies any straightforward interpretation of the plot. Indeed, while energetic pulsars do have low Fgamma/Fx values, little can be said for the bulk of the Fermi neutron stars. Dividing our pulsar sample into radio-loud and radio-quiet subsamples, we find that, on average, radio-quiet pulsars do have higher values of Fgamma/Fx, implying an intrinsec faintness of their X-ray emission and/or a different geometrical configuration. Moreover, despite the large spread mentioned above, statistical tests show a lower scatter in the radio-quiet dataset with respect to the radio-loud one, pointing to a somewhat more constrained geometry for the radio-quiet objects with respect to the radio-loud ones.