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8th of November 2023
ATNF Colloquium
Gamma-ray Emission from Nearby Stellar Flares and Undetected Pulsars
Yuzhe (Robert) Song (Swinburne University of Technology)
Abstract: The continuing survey of the gamma-ray sky by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope enables us to carry out population studies in gamma-rays. We developed novel stacking techniques to analyse Fermi-LAT data beyond the limit of point source sensitivity, which subsequently have been applied to various types of astrophysical sources.

So far, less than 10% of known pulsars are detected in gamma-rays. Stacking analysis of pulsars off the Galactic plane shows a significant detection, with a pulsar-like spectral index and a characteristic flux well below the Fermi-LAT point source sensitivity. Using COMPAS, a rapid binary population synthesis code, we provide a best fit model of distributions of pulsar properties at birth that can describe our observations.

Young ultra-cool dwarfs are extremely magnetically active and produce highly energetic flares, yet the Sun is the only isolated main sequence star detected in gamma-rays. We present a temporal analysis of red dwarf TVLM 513-46546 and reported periodicity in gamma-rays. Stacking Fermi-LAT data during flare events identified from optical and X-ray flare surveys reports an upper limit of flare gamma-ray emission. It likely originates from decay of neutral pions generated from the relativistic protons interacting within the stellar atmosphere. If confirmed, this could be catastrophic on exoplanet atmospheres and significantly reduces the habitability on these worlds.

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