uGMRT observations of the hot-Saturn WASP-69b: Radio-Loud Exoplanet–Exomoon Survey II (RLEES II)

Abstract

Exomoons have so far eluded ongoing searches. Several studies have exploited transit and transit timing variations and high-resolution spectroscopy to identify potential exomoon candidates. One method of detecting and confirming these exomoons is to search for signals of planet-moon interactions. In this work, we present the first radio observations of the exomoon candidate system WASP 69b. Based on the detection of alkali metals in the transmission spectra of WASP-69b, it was deduced that the system might be hosting an exomoon. WASP 69b is also one of the exoplanet systems that will be observed as part of JWST cycle-1 GTO. This makes the system an excellent target to observe and follow up. We observed the system for 32 hrs at 150 MHz and 218 MHz using the upgraded Giant Metrewave Radio Telescope (uGMRT). Though we do not detect radio emission from the systems, we place strong 3σ upper limits of 3.3 mJy at 150 MHz and 0.9 mJy at 218 MHz. We then use these upper limits to estimate the maximum mass loss from the exomoon candidate.

Exomoon Phase Curves: Toroidal Exosphere Simulations of Exo‐Ios Orbiting 8 Exoplanets in Alkali Spectroscopy

“…The exoplanet WASP‐69 b stands out as the most promising target among the considered systems due to its large column density ≥10 9 cm −2 . This high density exists in an environment with comparatively small radiation pressure and reasonably sized Alfvén sphere, featuring an estimated magnetic field strength of B p ∼ 15 G (Narang et al., 2023; Yadav & Thorngren, 2017). These factors contribute to the potential stability of a torus.…”

“…From the detection of alkali metals in the transmission spectra of WASP‐69 b, it was inferred that the system might be hosting an evaporating exomoon. Using the upgraded Giant Metrewave Radio Telescope (uGMRT), the system was probed for radio emissions at frequencies 150 and 218 MHz (Narang et al., 2023). Although only upper limits of 3.3 mJy ( ν = 150 MHz) and 0.9 mJy ( ν = 218 MHz) were attained with the uGMRT, the presence of an exomoon is still conceivable.…”

“…Current exoplanet magnetosphere models led Narang et al. (2023) to suggest the magnetic field strength to be roughly B p ∼ 15 G (Narang et al., 2023; Yadav & Thorngren, 2017). The candidate exoplanet‐exomoon system WASP‐69 b is set to be observed in eclipse by JWST cycle‐1 GTO, although a complementary infrared observation in transit would be invaluable for further exomoon analysis.…”

“…Less mass-loss, smaller exoplanet magnetic fields or strong temporal variations in emission could explain the radio-quiet behavior while still allowing the existence of an exomoon. Current exoplanet magnetosphere models led Narang et al (2023) to suggest the magnetic field strength to be roughly B p ∼ 15 G (Narang et al, 2023;Yadav & Thorngren, 2017). The candidate exoplanet-exomoon system WASP-69 b is set to be observed in eclipse by JWST cycle-1 GTO, although a complementary infrared observation in transit would be invaluable for further exomoon analysis.…”

Multiple Clues for Dayside Aerosols and Temperature Gradients in WASP-69 b from a Panchromatic JWST Emission Spectrum

“…Thus, the majority of Na line absorption studies at high spectral resolution mostly suggest an atmosphere with significant sodium, but the Na D 1 line is at least partially obscured by aerosols as compared to Na D 2 . WASP-69 b's Na detections have also been theorized to be potentially influenced by a volcanically active moon (Oza et al 2019); so far no moons have been detected (Narang et al 2023).…”