TESS asteroseismology of the known planet host star ? 2Fornacis

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 ?2 Fornacis, and following this to update the parameters of the orbiting planet ?2 For b. Methods. We measured the frequencies of the p-mode oscillations in ?2 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 ?2 For b and searched the residual radial velocities for remaining variability. Results. We find that ?2 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 ?2 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 ?2 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. © 2020 ESO.UID/FIS/04434/2019 RYC-2015-17697 80NSSC18K1585, 80NSSC19K0385 National Aeronautics and Space Administration, NASA W. M. Keck Foundation Horizon 2020 Framework Programme, H2020: 803193/BEBOP H2020 Marie Sk?odowska-Curie Actions, MSCA: 792848 UK Space Agency, UKSA European Research Council, ERC Danmarks Grundforskningsfond, DNRF: DNRF106, ESP2017-82674-R Generalitat de Catalunya Ministerio de Economía y Competitividad, MINECO: BES-2017-082610 Ministerio de Ciencia e Innovación, MICINN: 2017-SGR-1131 Instituto Nacional de Ciência e Tecnologia para Excitotoxicidade e Neuroproteção, INCT-EN European Regional Development Fund, FEDER Programa Operacional Temático Factores de Competitividade, POFC: POCI-01-0145-FEDER-030389, POCI-01-0145-FEDER03038, PTDC/FIS-AST/30389/2017Acknowledgements. The authors would like to thank J. P. Faria and H. Rein for useful discussions. This paper includes data collected by the TESS mission. MBN, WHB, MRS, AHMJT, and WJC acknowledge support from the UK Space Agency. AHMJT and MRS have benefited from funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no 803193/BEBOP). Funding for the Stellar Astrophysics Centre is funded by the Danish National Research Foundation (Grant agreement no.: DNRF106). ZÇO, MY, and SÖ acknowledge the Scientific and Technological Research Council of Turkey (TÜB?TAK:118F352). AS acknowledges support from grants ESP2017-82674-R (MICINN) and 2017-SGR-1131 (Generalitat Catalunya). TLC acknowledges support from the European Union’s Horizon 2020 research and innovation programme under the Marie Sk?odowska-Curie grant agreement No. 792848 (PULSATION). This work was supported by FCT/MCTES through national funds (UID/FIS/04434/2019). MD is supported by FCT/MCTES through national funds (PIDDAC) by this grant UID/FIS/04434/2019. MD and MV are supported by FEDER - Fundo Europeu de Desenvolvimento Regional through COMPETE2020 - Programa Operacional Competitividade e Internacionalização by these grants: UID/FIS/04434/2019; PTDC/FIS-AST/30389/2017 & POCI-01-0145-FEDER-030389 & POCI-01-0145-FEDER03038. MD is supported in the form of a work contract funded by national funds through Fundação para a Ciência e Tecnologia (FCT). SM acknowledges support by the Spanish Ministry with the Ramon y Cajal fellowship number RYC-2015-17697. BM and RAG acknowledge the support of the CNES/PLATO grant. DLB and LC acknowledge support from the TESS GI Program under awards 80NSSC18K1585 and 80NSSC19K0385. LGC thanks the support from grant FPI-SO from the Spanish Ministry of Economy and Competitiveness (MINECO) (research project SEV-2015-0548-17-2 and predoctoral contract BES-2017-082610). Funding for the TESS mission is provided by the NASA Explorer Program. Based in part on data acquired at the Anglo-Australian Telescope. We acknowledge the traditional owners of the land on which the AAT stands, the Gamilaraay people, and pay our respects to elders past and present. The data presented herein were in part obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community