Abstract
Detecting radio emission from stars has received increasing attention, be it for better understanding the structure and dynamics of our own Sun’s outer atmosphere or in the search for life on habitable extrasolar planets. There have been many targeted studies of radio emission from red M-type dwarf stars, as many exoplanets have been discovered orbiting them, while larger and hotter stars have often been completely neglected in radio studies.
The aim of this study is therefore to search for stellar emission in several radio surveys, thereby ridding us of the common bias towards M dwarf stars and known flare stars. Finding evidence of quiescent and flaring radio emission from hotter, and larger stars of spectral type G, F or A could lead to important insight into the activity and structure of the outer atmospheres of these stars. We here search archival observations from the six radio surveys GLEAM, LoTSS, TGSS, RACS, VLA FIRST and VLASS, with frequencies spanning from 72 MHz to 4 GHz, for stellar emission associated with known stars as registered in the Gaia DR3 stellar catalogue. The detected stars are filtered into fitting categories based on their position in the Hertzsprung-Russel diagram and their SIMBAD object types with single main sequence stars being the main focus of this project. stars, as many exoplanets have been discovered orbiting them, while larger and hotter stars have often been completely neglected in radio studies.
Our search for stellar emission has lead to many radio detections of single main sequence stars across all surveys except GLEAM. Many of the detections are not found to be previously reported. By relating the measured brightness temperature and/or radio luminosity to different stellar parameters and activity indicators, we find very similar relations across frequencies from 144 MHz to 3 GHz. The catalogues of detected stars in each of the surveys are very valuable as a basis for future observation time proposals, for which the measured fluxes and positions could be utilised. We also present many outlier stars, that show unusually high radio luminosities compared to similar stars, many of which would be interesting targets for future observations.
Supervisors:
- Professor Sven Wedemeyer, Institute of Theoretical Astrophysics, UiO (main-supervisor)
- Dr. Atul Mohan, Institute of Theoretical Astrophysics, UiO (co-supervisor)
Intern. assessor: Professor Øystein Elgarøy, Institute of Theoretical Astrophysics, UiO
Extern. assessor: Associate Professor Tobia Carozzi, Chalmers University