LRG-BEASTS: evidence for clouds in the transmission spectrum of HATS-46 b. Issue 4 (17th March 2023)

• Record Type: Journal Article
• Authors: Ahrer, E; Wheatley, P J; Gandhi, S; Kirk, J; King, G W; Louden, T; Welbanks, L
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 521:Issue 4(2023)
• Page Start: 5636
• Page End: 5644
• Publication Date: 2023-03-17
• Subjects: methods: observational -- techniques: spectroscopic -- planets and satellites: atmospheres -- planets and satellites: individual: HATS-46 b; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stad779
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We have performed low-resolution ground-based spectroscopy of HATS-46 b in transmission, using the EFOSC2 instrument on the ESO New Technology Telescope (NTT). HATS-46 b is a highly inflated exoplanet that is a prime target for transmission spectroscopy, having a Jupiter-like radius (0.95 R Jup ) but a much lower mass (0.16 M Jup ). It orbits a G-type star with a 4.7 d period, giving an equilibrium temperature of 1100 K. We observed one transit of HATS-46 b with the NTT, with the time-series spectra covering a wavelength range of 3900–9000 Å at a resolution (R) of ∼380. We achieved a remarkably precise transmission spectrum of 1.03 × photon noise, with a median uncertainty of 357 ppm for ∼200 Å-wide bins, despite the relative faintness of the host star with V mag = 13.6. The transmission spectrum does not show strong absorption features and retrievals favour a cloudy model, ruling out a clear atmosphere with 3.0σ confidence. We also place a conservative upper limit on the sodium abundance under the alternative scenario of a clear atmosphere. This is the eighth planet in the LRG-BEASTS (Low-Resolution Ground-Based Exoplanet Atmosphere Survey using Transmission Spectroscopy) survey, which uses 4 m-class telescopes such as the NTT to obtain low-resolution transmission spectra of hot Jupiters with precisions of around one atmospheric scale height.