Science Seminars

Detecting Gamma-ray Emission from Nearby Flare Stars

Speaker: Yuzhe (Robert) Song (CUNY/AMNH)
Date: Thursday, Oct 01, 2020
Time: 4:00 pm
Location: Zoom

Seminar Abstract:

The Sun is by far the only isolated main sequence star detected in gamma-rays, particularly during powerful flares. Young Ultra-cool dwarfs are far more magnetically active than the Sun, which makes them plausible gamma-ray sources. In this work we report possibly the first detection of a normal, isolated star in gamma-rays. With 12 years of Fermi-LAT data, we analyzed the phase-folded light curve of a fast-rotating radio star TVLM 513-46546 and report a tentative (TS=30) pulse, and refine its period. We examined the possibility of false positive by analyzing nearby Fermi catalog sources and test fields, repeating the analysis for different periods, and statistical validations. The gamma-ray pulse is almost in phase with the optical peak, and out of phase by 0.4 +/- 0.05 with the radio peak. This results argues for the emission from relativistic protons interacting with stellar atmospheres generating neutron pions that decay into gamma-ray photons. We also performed a stack survey on 97 radio and X-ray flare stars in the Solar neighborhood. Without any significant signals, modeling the upper limits shows a peak stellar flux at least a factor of 7 below the noise level.