A Search for Pulsations from Geminga Above 100 GeV with VERITAS

TL;DR

This study used VERITAS to search for very-high-energy gamma-ray pulsations from Geminga above 100 GeV, finding no significant emission and setting upper limits that constrain the pulsar's spectral behavior at these energies.

Contribution

First detailed search for pulsed gamma-ray emission from Geminga above 100 GeV using VERITAS, providing upper limits that inform models of pulsar emission spectra.

Findings

No significant pulsed emission detected above 100 GeV.

Upper limits constrain spectral hardening above 50 GeV.

Results inform models of high-energy pulsar emission.

Abstract

We present the results of 71.6 hours of observations of the Geminga pulsar (PSR J0633+1746) with the VERITAS very-high-energy gamma-ray telescope array. Data taken with VERITAS between November 2007 and February 2013 were phase-folded using a Geminga pulsar timing solution derived from data recorded by the XMM-\emph{Newton} and \emph{Fermi}-LAT space telescopes. No significant pulsed emission above 100 GeV is observed, and we report upper limits at the 95% confidence level on the integral flux above 135 GeV (spectral analysis threshold) of 4.0$\times10^{-13}$ s$^{-1}$ cm$^{-2}$ and 1.7$\times10^{-13}$ s$^{-1}$ cm$^{-2}$ for the two principal peaks in the emission profile. These upper limits, placed in context with phase-resolved spectral energy distributions determined from five years of data from the \emph{Fermi}-LAT, constrain possible hardening of the Geminga pulsar emission spectra above $\sim$50 GeV.