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A nova is a cataclysmic event on the surface of a white dwarf in a binary system that increases the overall brightness by several orders of magnitude. Although binary systems with a white dwarf are expected to be overabundant in globular clusters compared with in the Galaxy, only two novae from Galactic globular clusters have been observed. We present the discovery of an emission nebula in the Galactic globular cluster M 22 (NGC 6656) in observations made with the integral-field spectrograph MUSE. We extracted the spectrum of the nebula and used the radial velocity determined from the emission lines to confirm that the nebula is part of NGC 6656. Emission-line ratios were used to determine the electron temperature and density. It is estimated to have a mass of 1-17 x 10(-5) M-circle dot. This mass and the emission-line ratios indicate that the nebula is a nova remnant. Its position coincides with the reported location of a "guest star", an ancient Chinese term for transients, observed in May 48 BCE. With this discovery, this nova may be one of the oldest confirmed extra-solar events recorded in human history.
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 x 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.