VERITAS Observations of HESS J1943+213

TL;DR

This paper reports deep VERITAS gamma-ray observations of HESS J1943+213, providing the most significant detection so far, and discusses its classification as either an extreme BL Lac object or a young pulsar wind nebula.

Contribution

The study presents the deepest VHE gamma-ray observations of HESS J1943+213, confirming its detection and spectral properties, and analyzes multi-wavelength data to inform its classification.

Findings

Most significant VHE detection (~18 sigma) with VERITAS.

Source detected at ~2% Crab flux above 200 GeV.

No significant flux or spectral variability observed.

Abstract

HESS J1943+213 is a very-high-energy (VHE; >100 GeV) gamma-ray point source detected during the H.E.S.S. Galactic Plane Survey. Radio, infrared, X-ray, and GeV gamma-ray counterparts have been identified for HESS J1943+213; however, the classification of the source is still uncertain. Recent publications have argued primarily in favor of an extreme BL Lac object behind the Galactic plane, though the scenario that HESS J1943+213 is a young pulsar wind nebula is viable as well. We present deep VERITAS observations of HESS J1943+213, which provide the most significant VHE detection of the source so far, with ~18 sigma excess. The source is detected at ~2% Crab Nebula flux above 200 GeV with VERITAS, with the source spectrum well fit by a power-law function and showing agreement with the H.E.S.S. detection. We also include results from analysis of Swift XRT observations contemporaneous with VERITAS. No significant flux or spectral variability is detected with VERITAS or Swift XRT observations. We place the VERITAS results in a multi-wavelength context to comment on the HESS J1943+213 classification.