Investigating the TeV Morphology of MGRO J1908+06 with VERITAS

TL;DR

This paper presents deep VERITAS observations of the extended TeV gamma-ray source MGRO J1908+06, revealing its morphology, spectrum, and spatial extension, challenging previous associations with a pulsar wind nebula.

Contribution

The study provides detailed morphological and spectral analysis of MGRO J1908+06, offering new insights into its structure and emission mechanisms, and contrasting its spectral behavior with similar TeV sources.

Findings

Detected MGRO J1908+06 at 14 sigma significance

Measured a photon index of 2.20 +/- 0.10_stat +/- 0.20_sys

Found the source extension to be sigma_src = 0.44 +/- 0.02 degrees

Abstract

We report on deep observations of the extended TeV gamma-ray source MGRO J1908+06 made with the VERITAS very high energy (VHE) gamma-ray observatory. Previously, the TeV emission has been attributed to the pulsar wind nebula (PWN) of the Fermi-LAT pulsar PSR J1907+0602. We detect MGRO J1908+06 at a significance level of 14 standard deviations (14 sigma) and measure a photon index of 2.20 +/- 0.10_stat +/- 0.20_sys. The TeV emission is extended, covering the region near PSR J1907+0602 and also extending towards SNR G40.5--0.5. When fitted with a 2-dimensional Gaussian, the intrinsic extension has a standard deviation of sigma_src = 0.44 +/- 0.02 degrees. In contrast to other TeV PWNe of similar age in which the TeV spectrum softens with distance from the pulsar, the TeV spectrum measured near the pulsar location is consistent with that measured at a position near the rim of G40.5--0.5, 0.33 degrees away.