Utilizing a global network of telescopes to update the ephemeris for the highly eccentric planet HD 80606 b and to ensure the efficient scheduling of JWST

TL;DR

This study refines the orbital parameters of the highly eccentric exoplanet HD 80606 b using combined transit, radial velocity, and telescope data, enabling precise scheduling of JWST observations to study its atmospheric dynamics during periapsis.

Contribution

The paper provides an improved orbital ephemeris for HD 80606 b by integrating multiple observational methods, enhancing the accuracy of future JWST atmospheric studies.

Findings

Reduced timing uncertainty from tens of minutes to a few minutes.

Combined observational data significantly improved orbital model accuracy.

Enhanced scheduling precision for JWST transits and eclipses.

Abstract

The transiting planet HD80606b undergoes a 1000-fold increase in insolation during its 111-day orbit due to it being highly eccentric (e=0.93). The planet's effective temperature increases from 400K to over 1400K in a few hours as it makes a rapid passage to within 0.03AU of its host star during periapsis. Spectroscopic observations during the eclipse (which is conveniently oriented a few hours before periapsis) of HD80606b with the James Webb Space Telescope (JWST) are poised to exploit this highly variable environment to study a wide variety of atmospheric properties, including composition, chemical and dynamical timescales, and large scale atmospheric motions. Critical to planning and interpreting these observations is an accurate knowledge of the planet's orbit. We report on observations of two full-transit events: 7 February 2020 as observed by the TESS spacecraft and 7--8 December 2021 as observed with a worldwide network of small telescopes. We also report new radial velocity observations which when analyzed with a coupled model to the transits greatly improve the planet's orbital ephemeris. Our new orbit solution reduces the uncertainty in the transit and eclipse timing of the JWST era from tens of minutes to a few minutes. When combined with the planned JWST observations, this new precision may be adequate to look for non-Keplerian effects in the orbit of HD80606b.