Detection of Alpha Centauri at radio wavelengths: chromospheric emission and search for star-planet interaction
C. Trigilio, G. Umana, F. Cavallaro, C. Agliozzo, P. Leto, C.S. Buemi, A. Ingallinera, F. Bufano, S. Riggi
(Submitted on 22 Mar 2018)
At radio wavelengths, solar type stars emit thermal free-free and gyroresonance, gyrosynchrotron, and impulsive coherent emission. Thermal free-free emission originates at layers where the optical depth is close to unit, while high brightness temperature, variable emission, can be due to flares via gyrosynchrotron emission. We observed the alf Cen system with the Australian Telescope Compact Array at 2 GHz for three days and 17 GHz for one day. Both stars have been detected at 17 GHz, while only an upper limit has been obtained at low frequency despite the longest integration time. The brightness temperatures are consistent with the temperature of the upper chromosphere of the Sun. Inverting the formulae of the free-free emission, the average electron density of the plasma has been inferred. The same procedure was applied to the data in the millimetre recently taken with ALMA. A comparison with the atmospheric solar models reveals a higher level of activity in alf Cen B, even if still at quiescent level. The non detection at low frequency allow us to put a lower limit in the filling factor of active regions. The claimed detection of an Earth size planet in close orbit to alf Cen B, although doubtful, open the opportunity to check the existence of Star-Planet Magnetic Interaction (SPMI). This could trigger Auroral Radio Emission due to Electron Cyclotron Maser in the stellar corona, similar to the Jupiter-Io interaction, which is very intense, polarized and highly beamed. However, no hints of SPMI has been found.
Comments: Submitted to MNRAS, 9 pages, 8 Figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:1803.08338 [astro-ph.SR] (or arXiv:1803.08338v1 [astro-ph.SR] for this version)
Submission history
From: Corrado Trigilio
[v1] Thu, 22 Mar 2018 13:12:46 GMT (577kb,D)
https://arxiv.org/abs/1803.08338
