CANGAROO-III observation of TeV gamma rays from the unidentified gamma-ray source HESS J1614-518

TL;DR

This paper reports the detection of very high energy gamma rays from the unidentified source HESS J1614-518 using CANGAROO-III, supporting a hadronic origin possibly linked to a supernova remnant.

Contribution

First detection of TeV gamma rays from HESS J1614-518 with CANGAROO-III, providing spectral data and discussing possible astrophysical origins.

Findings

Gamma-ray emission detected above 760 GeV at 8.9 sigma

Spectrum fits a power-law with photon index 2.4

Hadronic origin from a supernova remnant is favored

Abstract

We report the detection, with the CANGAROO-III imaging atmospheric Cherenkov telescope array, of a very high energy gamma-ray signal from the unidentified gamma-ray source HESS J1614-518, which was discovered in the H.E.S.S. Galactic plane survey. Diffuse gamma-ray emission was detected above 760 GeV at the 8.9 sigma level during an effective exposure of 54 hr from 2008 May to August. The spectrum can be represented by a power-law: 8.2+-2.2_{stat}+-2.5_{sys}x10^{-12}x (E/1TeV)^{-Gamma} cm^{-2} s^{-1} TeV^{-1} with a photon index Gamma of 2.4+-0.3_{stat}+-0.2_{sys}, which is compatible with that of the H.E.S.S. observations. By combining our result with multi-wavelength data, we discuss the possible counterparts for HESS J1614-518 and consider radiation mechanisms based on hadronic and leptonic processes for a supernova remnant, stellar winds from massive stars, and a pulsar wind nebula. Although a leptonic origin from a pulsar wind nebula driven by an unknown pulsar remains possible, hadronic-origin emission from an unknown supernova remnant is preferred.