VERITAS Observations of the Nova in V407 Cygni

TL;DR

This paper reports on VHE gamma-ray observations of the nova in V407 Cygni, using the VERITAS telescope, and sets upper limits on gamma-ray flux, constraining particle acceleration models.

Contribution

It introduces an improved analysis technique for large zenith angle observations and provides the first VHE gamma-ray flux upper limits for V407 Cygni during its nova outburst.

Findings

No VHE gamma-ray detection was made.

Upper limit on flux at 1.6 TeV was established.

Results constrain models of particle acceleration in novae.

Abstract

We report on very high energy (E > 100 GeV) gamma-ray observations of V407 Cygni, a symbiotic binary that underwent a nova outburst producing 0.1-10 GeV gamma rays during 2010 March 10-26. Observations were made with the Very Energetic Radiation Imaging Telescope Array System during 2010 March 19-26 at relatively large zenith angles, due to the position of V407 Cyg. An improved reconstruction technique for large zenith angle observations is presented and used to analyze the data. We do not detect V407 Cygni and place a differential upper limit on the flux at 1.6 TeV of 2.3 \times 10^(-12) erg cm^(-2) s^(-1) (at the 95% confidence level). When considered jointly with data from Fermi-LAT, this result places limits on the acceleration of very high energy particles in the nova.