Blind search for radio-quiet and radio-loud gamma-ray pulsars with Fermi-LAT data

TL;DR

This study conducts a blind gamma-ray search with Fermi-LAT data to unbiasedly compare radio-quiet and radio-loud pulsars, revealing they are likely from the same population and estimating the radio-quiet fraction.

Contribution

It provides the first gamma-ray only blind search catalog of pulsars, measuring the radio-quiet fraction without observational bias, and compares their properties to test pulsar emission models.

Findings

Radio-quiet pulsars constitute about 64% of the sample.

No significant differences in age, flux, or location between the two groups.

Results support outer magnetosphere models over polar cap models.

Abstract

The Fermi Large Area Telescope (LAT) has observed more than a hundred of gamma-ray pulsars, about one third of which are radio-quiet, i.e. not detected at radio frequencies. The most of radio-loud pulsars are detected by Fermi LAT by using the radio timing models, while the radio-quiet ones are discovered in a blind search. The difference in the techniques introduces an observational selection bias and, consequently, the direct comparison of populations is complicated. In order to produce an unbiased sample, we perform a blind search of gamma-ray pulsations using Fermi-LAT data alone. No radio data or observations at optical or X-ray frequencies are involved in the search process. We produce a gamma-ray selected catalog of 25 non-recycled gamma-ray pulsars found in a blind search, including 16 radio-quiet and 9 radio-loud pulsars. This results in the direct measurement of the fraction of radio-quiet pulsars $\varepsilon_{RQ} = 64\pm 10\%$, which is in agreement with the existing estimates from the population modeling in the outer magnetosphere model. The Polar cap models are disfavored due to a lower expected fraction and the prediction of age dependence. The age, gamma-ray energy flux, spin-down luminosity and sky location distributions of the radio-loud and radio-quiet pulsars from the catalog do not demonstrate any statistically significant difference. The results indicate that the radio-quiet and radio-loud pulsars belong to one and the same population. The catalog shows no evidence for the radio beam evolution.