First Detection of Thermal Radio Emission from Solar-type Stars with the Karl G. Jansky Very Large Array
- Author(s)
- Jackie Villadsen, Gregg Hallinan, Stephen Bourke, Manuel Güdel, Michael P. Rupen
- Abstract
We present the first detections of thermal radio emission from the atmospheres of solar-type stars τ Cet, η Cas A, and 40 Eri A. These stars all resemble the Sun in age and level of magnetic activity, as indicated by X-ray luminosity and chromospheric emission in Ca II H and K lines. We observed these stars with the Karl G. Jansky Very Large Array with sensitivities of a few μJy at combinations of 10.0, 15.0, and 34.5 GHz. τ Cet, η Cas A, and 40 Eri A are all detected at 34.5 GHz with signal-to-noise ratios of 6.5, 5.2, and 4.5, respectively. 15.0 GHz upper limits imply a rising spectral index greater than 1.0 for τ Cet and 1.6 for η Cas A, at the 95% confidence level. The measured 34.5 GHz flux densities correspond to stellar disk-averaged brightness temperatures of roughly 10,000 K, similar to the solar brightness temperature at the same frequency. We explain this emission as optically thick thermal free-free emission from the chromosphere, with possible contributions from coronal gyroresonance emission above active regions and coronal free-free emission. These and similar quality data on other nearby solar-type stars, when combined with Atacama Large Millimeter/Submillimeter Array observations, will enable the construction of temperature profiles of their chromospheres and lower transition regions.
- Organisation(s)
- Department of Astrophysics
- External organisation(s)
- California Institute of Technology (Caltech), National Radio Astronomy Observatory Socorro
- Journal
- The Astrophysical Journal
- Volume
- 788
- No. of pages
- 8
- ISSN
- 0004-637X
- DOI
- https://doi.org/10.1088/0004-637X/788/2/112
- Publication date
- 05-2014
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103003 Astronomy, 103004 Astrophysics
- Keywords
- ASJC Scopus subject areas
- Astronomy and Astrophysics, Space and Planetary Science
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/8ecd5bde-a3dd-45d0-ab34-f4a0c29a82ad