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The TESS light curve of AI Phoenicis Maxted, P. F. L.; Gaulme, Patrick; Graczyk, D.; Heminiak, K. G.; Johnston, C.; Orosz, Jerome A.; Prša, Andrej; Southworth, John; Torres, Guillermo; Davies, Guy R.; Ball, Warrick; Chaplin, William J DOI: 10.1093/mnras/staa1662 License: None: All rights reserved
Document Version Publisher's PDF, also known as Version of record Citation for published version (Harvard): Maxted, PFL, Gaulme, P, Graczyk, D, Heminiak, KG, Johnston, C, Orosz, JA, Prša, A, Southworth, J, Torres, G, Davies, GR, Ball, W & Chaplin, WJ 2020, 'The TESS light curve of AI Phoenicis', Monthly Notices of the Royal Astronomical Society, vol. 498, no. 1, pp. 332–343. https://doi.org/10.1093/mnras/staa1662
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Download date: 28. Sep. 2021 MNRAS 498, 332–343 (2020) doi:10.1093/mnras/staa1662 Advance Access publication 2020 June 12
The TESS light curve of AI Phoenicis
P. F. L. Maxted, 1‹ Patrick Gaulme,2 D. Graczyk,3 K. G. Hełminiak ,3 C. Johnston ,4 Jerome A. Orosz,5 Andrej Prsa,ˇ 6 John Southworth,1 Guillermo Torres,7 Guy R. Davies,8,9 Warrick Ball 8,9 and William J Chaplin8,9 1
Astrophysics group, Keele University, Keele, Staordshire ST5 5BG, UK Downloaded from https://academic.oup.com/mnras/article/498/1/332/5856568 by University of Birmingham user on 09 October 2020 2Max-Planck-Institut fur¨ Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Gottingen,¨ Germany 3Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Rabianska´ 8, PL-87-100 Torun,´ Poland 4Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium 5Astronomy Department, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1221, USA 6Villanova University, Department of Astrophysics and Planetary Science, 800 Lancaster Avenue, Villanova, PA 19085, USA 7Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA 8School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK 9Stellar Astrophysics Centre (SAC), Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
Accepted 2020 June 8. Received 2020 June 6; in original form 2020 March 20
ABSTRACT Accurate masses and radii for normal stars derived from observations of detached eclipsing binary stars are of fundamental importance for testing stellar models and may be useful for calibrating free parameters in these model if the masses and radii are sufficiently precise and accurate. We aim to measure precise masses and radii for the stars in the bright eclipsing binary AI Phe, and to quantify the level of systematic error in these estimates. We use several different methods to model the Transiting Exoplanet Survey Satellite (TESS) light curve of AI Phe combined with spectroscopic orbits from multiple sources to estimate precisely the stellar masses and radii together with robust error estimates. We find that the agreement between different methods for the light-curve analysis is very good but some methods underestimate the errors on the model parameters. The semi-amplitudes of the spectroscopic orbits derived from spectra obtained with modern echelle´ spectrographs are consistent to within 0.1 per cent. The masses of the stars in AI Phe are M1 = 1.1938 ± 0.0008 M and M2 = 1.2438 ± 0.0008 M , and the radii are R1 = 1.8050 ± 0.0022 R and R2 = 2.9332 ± 0.0023 R . We conclude that it is possible to measure accurate masses and radii for stars in bright eclipsing binary stars to a precision of 0.2 per cent or better using photometry from TESS and spectroscopy obtained with modern echelle´ spectrographs. We provide recommendations for publishing masses and radii of eclipsing binary stars at this level of precision. Key words: binaries: eclipsing – stars: fundamental parameters – stars: individual: AI Phe – stars: solar-type.
and new uvby light curves, and a spectroscopic estimate of the metal 1 INTRODUCTION abundance ([Fe/H] =−0.14 ± 0.1). The analysis by Andersen et al. AI Phe is a moderately bright (V = 8.6) star that was first noted as an has been the definitive observational study of AI Phe until recently eclipsing binary by Strohmeier (1972). Photometric monitoring by and the absolute parameters derived therein have often been used Reipurth (1978) established that the orbital period is approximately as a benchmark for testing stellar evolution models of single stars 24.59 d and that the primary eclipse is total. Hrivnak & Milone (e.g. Andersen et al. 1988;Polsetal.1997; Ribas, Jordi & Gimenez´ (1984) obtained UBVRI light curves of AI Phe, covering both 2000; Lastennet & Valls-Gabaud 2002; Spada et al. 2013;Ghezzi& eclipses and combined their analysis of these light curves with the Johnson 2015; Higl & Weiss 2017). spectroscopic orbits for both stars published by Imbert (1979)to Kirkby-Kent et al. (2016) used light curves obtained during the measure the masses and radii of both components. They found that WASP exoplanet transit survey together with improved spectroscopic the stars in AI Phe are slightly more massive than the Sun, and both orbits for both components by Hełminiak et al. (2009) to improve have evolved away from the zero-age main sequence, with the more the precision of the radius measurements for both components of massive star being a subgiant. A much-improved spectroscopic orbit AI Phe to better than 1 per cent. Sybilski et al. (2018) also obtained for AI Phe was published by Andersen et al. (1988) together with a spectroscopic orbits for both components of AI Phe together with re-analysis of the UBVRI light curves by Hrivnak & Milone (1984) spectroscopic observations obtained during the secondary eclipse that show that the rotation axis of the subgiant component is not aligned with the orbital axis of the binary system. Gallenne et al. E-mail: [email protected] (2019) have used the VLTI interferometer to measure the astrometric