Discovery of TeV Gamma-ray Emission from CTA 1 by VERITAS

TL;DR

This paper reports the discovery of TeV gamma-ray emission from the supernova remnant CTA 1 using VERITAS, providing insights into the PWN origin of high-energy photons associated with the SNR.

Contribution

First detection of TeV gamma-ray emission from CTA 1, characterizing its spectrum, morphology, and linking it to the pulsar wind nebula origin.

Findings

Detected extended TeV gamma-ray emission with 6.5 sigma significance.

Measured a power-law spectrum with index 2.2 and normalization 9.1e-14.

The TeV flux is about 0.2% of the pulsar's spin-down power.

Abstract

We report the discovery of TeV gamma-ray emission coincident with the shell-type radio supernova remnant (SNR) CTA 1 using the VERITAS gamma-ray observatory. The source, VER J0006+729, was detected as a 6.5 standard deviation excess over background and shows an extended morphology, approximated by a two-dimensional Gaussian of semi-major (semi-minor) axis 0.30 degree (0.24 degree) and a centroid 5' from the Fermi gamma-ray pulsar PSR J0007+7303 and its X-ray pulsar wind nebula (PWN). The photon spectrum is well described by a power-law dN/dE = N_0 (E/3 TeV)^(-\Gamma), with a differential spectral index of \Gamma = 2.2 +- 0.2_stat +- 0.3_sys, and normalization N_0 = (9.1 +- 1.3_stat +- 1.7_sys) x 10^(-14) cm^(-2) s^(-1) TeV^(-1). The integral flux, F_\gamma = 4.0 x 10^(-12) erg cm^(-2) s^(-1) above 1 TeV, corresponds to 0.2% of the pulsar spin-down power at 1.4 kpc. The energetics, co-location with the SNR, and the relatively small extent of the TeV emission strongly argue for the PWN origin of the TeV photons. We consider the origin of the TeV emission in CTA 1.