TESS asteroseismology of the known planet host star λ² Fornacis

Abstract

Context. The Transiting Exoplanet Survey Satellite (TESS) is observing bright known planet-host stars across almost the entire sky. These stars have been subject to extensive ground-based observations, providing a large number of radial velocity measurements. Aims. The objective of this work is to use the new TESS photometric observations to characterize the star λ2 Fornacis, and following this to update the parameters of the orbiting planet λ2 For b. Methods. We measured the frequencies of the p-mode oscillations in λ2 For, and in combination with non-seismic parameters estimated the stellar fundamental properties using stellar models. Using the revised stellar properties and a time series of archival radial velocities from the UCLES, HIRES and HARPS instruments spanning almost 20 years, we refit the orbit of λ2 For b and searched the residual radial velocities for remaining variability. Results. We find that λ2 For has a mass of 1.16 ± 0.03 M⊙ and a radius of 1.63 ± 0.04 R⊙, with an age of 6.3 ± 0.9 Gyr. This and the updated radial velocity measurements suggest a mass of λ2 For b of 16.8−1.3+1.2 M⊕, which is ∼5M⊕ less than literature estimates. We also detect an additional periodicity at 33 days in the radial velocity measurements, which is likely due to the rotation of the host star. Conclusions. While previous literature estimates of the properties of λ2 For are ambiguous, the asteroseismic measurements place the star firmly at the early stage of its subgiant evolutionary phase. Typically only short time series of photometric data are available from TESS, but by using asteroseismology it is still possible to provide tight constraints on the properties of bright stars that until now have only been observed from the ground. This prompts a reexamination of archival radial velocity data that have been accumulated in the past few decades in order to update the characteristics of the planet hosting systems observed by TESS for which asteroseismology is possible.

On the application of machine learning in astronomy and astrophysics: A text‐mining‐based scientometric analysis

“…The violet group contains authors focused on the application of AI/ML in the search for exoplanets, such as William J. Borucki (43 co‐citations) from the California Institute of Technology (Borucki et al, 2010); Jon M. Jenkins (40 co‐citations) from the NASA Ames Research Center (Ansdell et al, 2018); and Benoit Mosser (32 co‐citations) from the Observatoire de Paris: Laboratory for Space Studies and Instrumentation in Astrophysics (Nielsen et al, 2020).…”

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Magnetic and Rotational Evolution of $ρ$ CrB from Asteroseismology with TESS

“…TESS observed ρ CrB in 2-minute cadence for a total of approximately 52 days during Sectors 24 and 25 of Cycle 2 (2020 Apr 15 -2020 Jun 08). We downloaded the PDC-MAP SPOC light curve (Jenkins et al 2016), but also derived our own light curve following the procedure described in Nielsen et al (2020) and Buzasi et al (2015) in hopes of improving on the noise level in the SPOC product. We treated sectors individually, masking cadences with nonzero quality flags.…”