We started by developing a Gaussian process regression framework to model granulation and oscillations in red-giant stars. This method is capable of describing stellar signals while simultaneously modeling an exoplanet's transit. The implementation of the method was described in Pereira, Campante et al. (2019,
https://arxiv.org/abs/1908.10662(s’ouvre dans une nouvelle fenêtre)) and the corresponding software tool (gptransits) made freely available through GitHub.
The open-source software eleanor was then used to produce photometric time series for all available sectors of TESS data for each target star. We conducted an automated transit search on TESS light curves of approximately 100,000 red giants, with a focus on close-in giant planets. The automated search procedure was extensively tested prior to the first science data release (Campante et al. 2018,
https://zenodo.org/record/2463210#.X7fZLdW2yOE(s’ouvre dans une nouvelle fenêtre)). The transit search was complemented by a vetting and ranking procedure aimed at distinguishing the expected transit-like features from astrophysical false positives and systematic false alarms. The first detection of a TESS giant planet transiting an oscillating red giant was reported in Huber et al. (2019,
https://arxiv.org/abs/1901.01643(s’ouvre dans une nouvelle fenêtre)). This was followed by the detection of a warm sub-Saturn around an evolved F-type star (Addison et al. 2020,
https://arxiv.org/abs/2001.07345(s’ouvre dans une nouvelle fenêtre)).
Furthermore, a total of three known radial-velocity planets were discovered to transit from TESS observations (Kane et al. 2020,
https://arxiv.org/abs/2007.10995(s’ouvre dans une nouvelle fenêtre); Pepper et al. 2020,
https://arxiv.org/abs/1911.05150(s’ouvre dans une nouvelle fenêtre)). The number of radial-velocity planets found to transit during TESS's primary mission is aligned with the predictions of Dalba et al. (2019,
https://arxiv.org/abs/1811.06550(s’ouvre dans une nouvelle fenêtre)).
TESS's excellent photometric precision enables asteroseismology of red-giant stars (Schofield et al. 2019,
https://arxiv.org/abs/1901.10148(s’ouvre dans une nouvelle fenêtre)). TESS photometry thus offers the prospect of conducting asteroseismology of evolved host stars (Kane, Bean, Campante et al. 2020,
https://arxiv.org/abs/2010.15164(s’ouvre dans une nouvelle fenêtre)). We estimated global asteroseismic parameters by applying Fourier-based automated methods (Campante et al. 2019,
https://arxiv.org/abs/1909.05961(s’ouvre dans une nouvelle fenêtre)) to the frequency-power spectra of the target stars. These methods had previously been extensively applied to Kepler/K2 data (Chontos et al. 2019,
https://arxiv.org/abs/1903.01591(s’ouvre dans une nouvelle fenêtre); Kuszlewicz et al. 2019a,
https://arxiv.org/abs/1905.00040(s’ouvre dans une nouvelle fenêtre); Kuszlewicz et al. 2019b,
https://arxiv.org/abs/1907.01565(s’ouvre dans une nouvelle fenêtre); Santos, Campante et al. 2019,
https://arxiv.org/abs/1908.02897(s’ouvre dans une nouvelle fenêtre); Thomas et al. 2019,
https://arxiv.org/abs/1903.04998(s’ouvre dans une nouvelle fenêtre)). TESS first-light results (Silva Aguirre et al. 2020,
https://arxiv.org/abs/1912.07604(s’ouvre dans une nouvelle fenêtre)) in the buildup to which these same methods were employed, clearly demonstrated the potential of TESS for carrying out asteroseismic ensemble studies of red giants. This potential was recently realized by using TESS asteroseismology to age date the early merging of the Milky Way with the Gaia-Enceladus dwarf galaxy (Chaplin et al. 2020,
https://arxiv.org/abs/2001.04653(s’ouvre dans une nouvelle fenêtre)).
We next determined fundamental stellar properties through a grid-based, forward modeling approach using the Bayesian code AIMS (Rendle et al. 2019,
https://arxiv.org/abs/1901.02663(s’ouvre dans une nouvelle fenêtre)). To ensure that fundamental properties are derived with the highest possible accuracy, we explored the impact of key physical processes, as well as of the chemical composition (Adibekyan et al. 2020,
https://arxiv.org/abs/2008.08371(s’ouvre dans une nouvelle fenêtre)) on the stellar properties inferred from forward modeling (Nsamba, Campante et al. 2018,
https://arxiv.org/abs/1812.00431(s’ouvre dans une nouvelle fenêtre); Nsamba, Campante et al. 2019,
https://arxiv.org/abs/1904.01560(s’ouvre dans une nouvelle fenêtre); Nsamba, Moedas, Campante et al. 2020,
https://arxiv.org/abs/2010.07593(s’ouvre dans une nouvelle fenêtre)).
Moreover, several known evolved hosts have benefited from TESS's precision photometry. Campante et al. (2019,
https://arxiv.org/abs/1909.05961(s’ouvre dans une nouvelle fenêtre)) reported the first detections of oscillations in known hosts by TESS. Other detections of solar-like oscillations in known hosts were reported by Ball et al. (2020,
https://arxiv.org/abs/2010.07323(s’ouvre dans une nouvelle fenêtre)) Jiang et al. (2020,
https://arxiv.org/abs/2005.00272(s’ouvre dans une nouvelle fenêtre)) and Nielsen et al. (2020,
https://arxiv.org/abs/2007.00497(s’ouvre dans une nouvelle fenêtre)).
An online catalog of planet candidates and their host stars is currently being assembled and will be hosted at the VizieR catalog service. It will combine the scientific output of the transit photometry, asteroseismology and ground-based follow-up (whenever available).
Finally, we carried out a nationwide educational/outreach program as part of a secondment at Ciência Viva, the Portuguese national agency for the promotion of science and technology. The program consisted of a series of Café Scientifique-like events on various topics of modern astrophysics targeting the general public (12 events in total across Portugal).
