Year: 2025
Type: article
Abstract: ABSTRACT We carried out the first high-resolution transit observations of the exoplanet WASP-49 Ab with Keck/HIRES. Upon custom wavelength calibration we achieve a Doppler RV precision of $<$ 60 ${\rm m\, s}^{-1}$. This is an improvement in RV stability of roughly 240 ${\rm m\, s}^{-1}$ with respect to the instrument standard. We report an average sodium flux residual of $\Delta \mathcal {F}_{\rm NaD}/ \mathcal {F}_{\star } (\lambda) \sim$ 3.2 $\pm$ 0.4 per cent (8.0$\sigma$) comparable to previous studies. Interestingly, an average Doppler shift of −6.2 $\pm$ 0.5 ${\rm km\, s}^{-1}$ (12.4 $\sigma$) is identified offset from the exoplanet rest frame. The velocity residuals in time trace a blueshift (v$_{\Gamma , \rm ingress} \sim$ −10.3 $\pm$ 1.9 ${\rm km\, s}^{-1}$) to redshift (v$_{\Gamma , \rm egress} \sim$ + 4.1 $\pm$ 1.5 ${\rm km\, s}^{-1}$) suggesting the origin of the observed sodium is unlikely from the atmosphere of the planet. The average Na light curves indicate a depth of $\Delta \mathcal {F}_{\rm NaD} /\mathcal {F}_{\star } (t) \sim$ 0.47 $\pm$ 0.04 per cent (11.7 $\sigma$) enduring $\lesssim$ 90 min with a half-max duration of $\sim$ 40.1 min. Frequent high-resolution spectroscopic observations will be able to characterize the periodicity of the observed Doppler shifts. Considering the origin of the transient sodium gas is of unknown geometry, a co-orbiting natural satellite may be a likely source.
Institutions: Indian Institute of Astrophysics, University of California, Santa Cruz, California Institute of Technology, Jet Propulsion Laboratory, Lund University, European Southern Observatory, European Southern Observatory, Boston University, NASA Exoplanet Science Institute, Infrared Processing and Analysis Center, Ghent University, University of Bern, University of Oxford
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $1,451
OpenAlex ID: W4409277698