Doppler shifted transient sodium detection by KECK/HIRES

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.

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Journal
Monthly Notices of the Royal Astronomical Society Letters
Published
2025-03-26
DOI
https://doi.org/10.1093/mnrasl/slaf031
Citations
2
Primary Topic
Magnetic Field Sensors Techniques
Type
article
Field-Weighted Citation Impact
1.46

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article

Doppler shifted transient sodium detection by KECK/HIRES

J. V. Seidel, H. J. Hoeijmakers, Carl Schmidt, Andrea Gebek et al.
2 citations
Monthly Notices of the Royal Astronomical Society Letters
Magnetic Field Sensors Techniques
1.46
article

Doppler shifted transient sodium detection by KECK/HIRES

J. V. Seidel, H. J. Hoeijmakers, Carl Schmidt, Andrea Gebek, Moritz Meyer zu Westram, A. Oza, Chloe Fisher, Katherine de Kleer, Ashley Baker, Aurora Y. Kesseli, Steph Sallum, Aaron Bello-Arufe, Athira Unni, Manjunath Bestha, T. Sivarani
article en
2 citations

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.

Monthly Notices of the Royal Astronomical Society LettersVol. 540(1)
Boston University (US), University of Bern (CH), California Institute of Technology (US), Jet Propulsion Laboratory (US), Indian Institute of Astrophysics (IN), University of California, Santa Cruz (US), Lund University (SE), NASA Exoplanet Science Institute (US), Ghent University (BE), University of Oxford (GB), Geneeskundige en Gezondheidsdienst (NL), Institute of Applied Physics (MD), European Southern Observatory (CL), Astronomical Institute of the Slovak Academy of Sciences (SK), Astronomy and Space (AU), Infrared Processing and Analysis Center (US)
National Aeronautics and Space Administration, W. M. Keck Foundation, California Institute of Technology, Jet Propulsion Laboratory
Openalex Percentile: Top 18%
Magnetic Field Sensors Techniques
1.46
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