Search for MeV Gamma-ray emission from TeV bright red dwarfs with COMPTEL

TL;DR

This study searched for MeV gamma-ray emission from eight TeV bright red dwarfs using COMPTEL data, finding no significant signals but setting upper limits on their gamma-ray fluxes, and discussing contamination issues.

Contribution

First comprehensive search for MeV gamma-ray emission from TeV bright red dwarfs using archival COMPTEL data, establishing flux upper limits and addressing source contamination.

Findings

No statistically significant MeV gamma-ray detection from the red dwarfs.

Set 95% confidence level upper limits on gamma-ray fluxes.

Contamination from nearby bright sources affects detection confidence.

Abstract

The SHALON atmospheric Cherenkov telescope has detected very high energy gamma-ray emission at TeV energies from eight red dwarfs, namely, V388 Cas, V547 Cas, V780 Tau, V962 Tau, V1589 Cyg, GJ 1078, GJ 3684 and GL 851.1. Consequently, these red dwarfs have been suggested as sources of ultra-high energy cosmic rays. In this work, we search for soft gamma-ray emission from these TeV bright red dwarfs between 0.75-30 MeV using archival data from the COMPTEL gamma-ray imaging telescope, as a follow-up to a similar search for GeV gamma-ray emission using the Fermi-LAT telescope. Although, prima-facie, we detect non-zero photon flux from three red dwarfs with high significance, these signals can attributed to contamination from nearby sources such as Crab and Cygnus, which are within the angular resolution of COMPTEL, and have been previously detected as very bright point sources at MeV energies. Therefore, we could not detect any statistically significant signal ($>3\sigma$) from any of these eight red dwarfs from 0.75-30 MeV. We then report the 95% confidence level upper limits on the differential photon flux (at 30 MeV), integral photon flux and integral energy flux for all of the eight red dwarfs. The integral energy flux limits range between $10^{-11}-10^{-10} \rm{ergs/cm^2/s}$.