Searching for star-planet interactions in GJ 486 at radio wavelengths with the uGMRT

¹ IAA-CSIC, Instituto de Astrofísica de Andalucía, Glorieta de la Astronomía s/n, 18008 Granada, Spain
² School of Sciences, European University Cyprus, Diogenes street, Engomi, 1516 Nicosia, Cyprus
³ Cooperative Programs for the Advancement of Earth System Science, University Corporation for Atmospheric Research, Boulder, CO, USA
⁴ ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, Dwingeloo, 7991 PD, The Netherlands
⁵ Anton Pannekoek Institute for Astronomy, University of Amsterdam, 1090 GE Amsterdam, The Netherlands
⁶ Academia Sinica Institute of Astronomy & Astrophysics, Taipei 10617, Taiwan
⁷ Goddard Space Flight Center, Greenbelt, MD, USA
⁸ INAF-Osservatorio Astrofisico di Catania, Via Santa Sofia 78, 95123 Catania, Italy
⁹ Centro de Astrobiología (CSIC-INTA), Campus ESAC, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain

^★ Corresponding author; lpm@iaa.es

Received: 8 August 2024
Accepted: 21 November 2024

Abstract

Aims. We search for radio emission from star–planet interactions in the M dwarf system GJ 486, which hosts an Earth-like planet.

Methods. We observed the GJ 486 system with the upgraded Giant Metrewave Radio Telescope (uGMRT) from 550 to 750 MHz in nine different epochs between October 2021 and February 2022, covering almost all orbital phases of GJ 486b from different orbital cycles. We obtained radio images and dynamic spectra of the total and circularly polarized intensity for each individual epoch.

Results. We did not detect any quiescent radio emission in any epoch above 3σ. Similarly, we did not detect any bursty emission in our dynamic spectra.

Conclusions. While we cannot completely rule out that the absence of a radio detection is due to time variability of the radio emission or to the maximum electron-cyclotron maser emission being below our observing range, these cases seem unlikely. We discuss two possible scenarios: an intrinsic dim radio signal and, alternatively, a situation where the anisotropic beamed emission is pointed away from the observer. If the non-detection of radio emission from the star-planet interaction in GJ 486 is due to an intrinsically dim signal, this implies that independent of whether the planet is magnetized or not, the mass-loss rate is small (Ṁ_⋆ ≲ 0.3 Ṁ_⊙) and that, concomitantly, the efficiency of the conversion of the Poynting flux into radio emission must be low (β ≲ 10⁻³). Free-free absorption effects are negligible, given the high value of the coronal temperature. Finally, if the anisotropic beaming pointed away from the observer, this would imply that GJ 486 has very low values of magnetic obliquity and inclination.