Observation of Extended VHE Emission from the Supernova Remnant IC 443 with VERITAS

TL;DR

This paper reports the detection of extended very-high-energy gamma-ray emission from supernova remnant IC 443 using VERITAS, providing insights into cosmic ray acceleration and interactions with molecular clouds.

Contribution

First detection of extended VHE gamma-ray emission from IC 443, with detailed spectral and morphological analysis using VERITAS observations.

Findings

Emission is extended with a size of ~0.16 degrees.

Spectrum follows a power law with index ~3.

Flux above 300 GeV measured at approximately 4.6 x 10^-12 cm^-2 s^-1.

Abstract

We present evidence that the very-high-energy (VHE, E > 100 GeV) gamma-ray emission coincident with the supernova remnant IC 443 is extended. IC 443 contains one of the best-studied sites of supernova remnant/molecular cloud interaction and the pulsar wind nebula CXOU J061705.3+222127, both of which are important targets for VHE observations. VERITAS observed IC 443 for 37.9 hours during 2007 and detected emission above 300 GeV with an excess of 247 events, resulting in a significance of 8.3 standard deviations (sigma) before trials and 7.5 sigma after trials in a point-source search. The emission is centered at 06 16 51 +22 30 11 (J2000) +- 0.03_stat +- 0.08_sys degrees, with an intrinsic extension of 0.16 +- 0.03_stat +- 0.04_sys degrees. The VHE spectrum is well fit by a power law (dN/dE = N_0 * (E/TeV)^-Gamma) with a photon index of 2.99 +- 0.38_stat +- 0.3_sys and an integral flux above 300 GeV of (4.63 +- 0.90_stat +- 0.93_sys) * 10^-12 cm^-2 s^-1. These results are discussed in the context of existing models for gamma-ray production in IC 443.