First Results on RR Lyrae Stars with the TESS Space Telescope: Untangling the Connections between Mode Content, Colors, and Distances

Creators: Molnár, L.; Bódi, A.; Pál, A.; Bhardwaj, A.; Hambsch, F.-J.; Benkő, J. M.; Derekas, A.; Ebadi, M.; Joyce, M.; Hasanzadeh, A.; Kolenberg, K.; Lund, M. B.; Nemec, J. M.; Netzel, H.; Ngeow, C.-C.; Pepper, J.; Plachy, E.; Prudil, Z.; Siverd, R. J.; Skarka, M.; Smolec, R.; Sódor, Á.; Sylla, S.; Szabó, P.; Szabó, R.; Kjeldsen, H.; Christensen-Dalsgaard, J.; Ricker, G. R.

Abstract

The Transiting Exoplanet Survey Satellite (TESS) space telescope is collecting continuous, high-precision optical photometry of stars throughout the sky, including thousands of RR Lyrae stars. In this paper, we present results for an initial sample of 118 nearby RR Lyrae stars observed in TESS Sectors 1 and 2. We use differential image photometry to generate light curves and analyze their mode content and modulation properties. We combine accurate light-curve parameters from TESS with parallax and color information from the Gaia mission to create a comprehensive classification scheme. We build a clean sample, preserving RR Lyrae stars with unusual light-curve shapes, while separating other types of pulsating stars. We find that a large fraction of RR Lyrae stars exhibit various low-amplitude modes, but the distribution of those modes is markedly different from those of the bulge stars. This suggests that differences in physical parameters have an observable effect on the excitation of extra modes, potentially offering a way to uncover the origins of these signals. However, mode identification is hindered by uncertainties when identifying the true pulsation frequencies of the extra modes. We compare mode amplitude ratios in classical double-mode stars to stars with extra modes at low amplitudes and find that they separate into two distinct groups. Finally, we find a high percentage of modulated stars among the fundamental mode pulsators, but also find that at least 28% of them do not exhibit modulation, confirming that a significant fraction of stars lack the Blazhko effect.

Additional Information

© 2021. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 June 19; revised 2021 September 14; accepted 2021 September 14; published 2021 December 22. This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Science Mission Directorate. This work has made use of data from the European Space Agency (ESA) mission Gaia, processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. L.M. was supported by the Premium Postdoctoral Research Program of the Hungarian Academy of Sciences. The research leading to these results has received funding from the LP2012-31, LP2014-17 and LP2018-7 Lendület grants of the Hungarian Academy of Sciences and from the "SeismoLab" KKP-137523 Élvonal and NN-129075 grants of the Hungarian Research, Development and Innovation Office (NKFIH). The work reported on in this publication has been partially supported by COST Action CA18104: MW–Gaia. A.P. acknowledges the MIT Kavli Center and the Kavli Foundation for their hospitality during stays at MIT, and the NASA contract number NNG14FC03C. A.B. acknowledges a Gruber fellowship 2020 grant sponsored by the Gruber Foundation and the International Astronomical Union and is supported by the EACOA Fellowship Program under the umbrella of the East Asia Core Observatories Association, which consists of the Academia Sinica Institute of Astronomy and Astrophysics, the National Astronomical Observatory of Japan, the Korea Astronomy and Space Science Institute, and the National Astronomical Observatories of the Chinese Academy of Sciences. M.J. was supported by the Lasker Data Science Postdoctoral Fellowship of the STScI and by the Research School of Astronomy and Astrophysics at the Australian National University and funding from Australian Research Council grant No. DP150100250. She was likewise supported by generous visitation funding from Konkoly Observatory through the LP2014-17 Lendület grant. C.C.N. thanks the funding from Ministry of Science and Technology (Taiwan) under the contract 109–2112–M–008–014–MY3. E.P. was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences. Z.P. acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 138713538—SFB 881 ("The Milky Way System," subproject A11). R.S. was supported by the National Science Center, Poland, Sonata BIS project 2018/30/E/ST9/00598. M.S. acknowledges the financial support of the Operational Program Research, Development and Education—Project Postdoc@MUNI (No. CZ.02.2.69/0.0/0.0/16_027/0008360) and the MSMT Inter Transfer program LTT20015. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (grant agreement no. DNRF106). We gratefully acknowledge the grant from the European Social Fund via the Lithuanian Science Council (LMTLT) grant No. 09.3.3-LMT-K-712-01-0103. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France, the International Variable Star Index (VSX) database, operated at AAVSO, Cambridge, Massachusetts, USA, and NASA's Astrophysics Data System (ADS). Facilities: TESS (Ricker et al. 2015), Gaia (Gaia Collaboration et al. 2016), SIMBAD (Wenger et al. 2000), VSX. Software: fitsh (Pál 2012), lightkurve (Barentsen et al. 2019), Period04 (Lenz & Breger 2005), gnuplot, mwdust (Bovy et al. 2016), galpy (Bovy 2015), echelle_toggler (Joyce 2021), Astropy (Astropy Collaboration et al. 2013, 2018).

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