Publication: HORuS transmission spectroscopy and revised planetary parameters of KELT-7 b
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Oxford University Press.
We report on the high-resolution spectroscopic observations of two planetary transits of the hot Jupiter KELT-7b (Mp = 1.28 +/- 0.17Mjup, Teq=2028 K) observed with the High Optical Resolution Spectrograph (HORuS) mounted on the 10.4-m Gran Telescopio Canarias (GTC). A new set of stellar parameters are obtained for the rapidly rotating parent star from the analysis of the spectra. Using the newly derived stellar mass and radius, and the planetary transit data of the Transiting Exoplanet Survey Satellite (TESS) together with the HORuS velocities and the photometric and spectroscopic data available in the literature, we update and improve the ephemeris of KELT-7b. Our results indicate that KELT-7 has an angle Lamda = -10.55 +/- 0.27 deg between the sky projections of the star’s spin axis and the planet’s orbital axis. By combining this angle and our newly derived stellar rotation period of 1.38 +/- 0.05 d, we obtained a 3D obliquity Psi = 12.4 +/- 11.7 deg (or 167.6 deg), thus reinforcing that KELT-7 is a well-aligned planetary system. We search for the presence of Halfa, Li i, Na i, Mg i, and Ca ii features in the transmission spectrum of KELT-7b but we are only able to determine upper limits of 0.08–1.4 % on their presence after accounting for the contribution of the stellar variability to the extracted planetary spectrum. We also discuss the impact of stellar variability in the planetary data. Our results reinforce the importance of monitoring the parent star when performing high-resolution transmission spectroscopy of the planetary atmosphere in the presence of stellar activity.
© 2021 The Authors. The authors acknowledge the HORuS project team for its effort and dedication to the HORuS instrument. We acknowledge financial support from the Agencia Estatal de Investigación of the Ministerio de Ciencia, Innovación y Universidades through projects PID2019- 109522GB-C51,54, and the Centre of Excellence “María de Maeztu” award to Centro de Astrobiología (MDM-2017-0737). CAP, JIGH and RR acknowledge financial support from the Spanish Ministry MICINN projects AYA2017-86389-P, PID2020-117493GB-I00, and the Spanish Ministry of Science and Innovation under the FEDER Agreement INSIDE-OOCC (ICTS-2019-03-IAC-12). JIGH also acknowledges financial support from the Spanish Ministry of Science and Innovation (MICINN) under the 2013 Ramón y Cajal program RYC-2013-14875. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC,https: //www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institution participating in the Gaia Multilateral Agreement. This research made use of the Vienna Atomic Line Database operated at Uppsala University, the Institute of Astronomy RAS in Moscow,and the University of Vienna. This paper includes data collected with the TESS mission, obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the TESS mission is provided by the NASA Explorer Program. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555. This research made use of Astropy,22 a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013, 2018). Based on observations made with the Gran Telescopio Canarias (GTC), installed at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias on the island of La Palma. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This publication makes use of VOSA, developed under the Spanish Virtual Observatory project supported by the Spanish MINECO through grant AyA2017-84089. VOSA has been partially updated by using funding from the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement nº 776403 (EXOPLANETS-A).