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Published January 31, 2023 | Submitted
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15000 Ellipsoidal Binary Candidates in TESS: Orbital Periods, Binary Fraction, and Tertiary Companions

Abstract

We present a homogeneously-selected sample of 15779 candidate binary systems with main sequence primary stars and orbital periods shorter than 5 days. The targets were selected from TESS full-frame image lightcurves on the basis of their tidally-induced ellipsoidal modulation. Spectroscopic follow-up suggests a sample purity of 83 ± 13 per cent. Injection-recovery tests allow us to estimate our overall completeness as 28 ± 3 per cent with P_(orb) < 3 days and to quantify our selection effects. We estimate that 39 ± 4 per cent of our sample are contact binary systems, and we disentangle the period distributions of the contact and detached binaries. We derive the orbital period distribution of the main sequence binary population at short orbital periods, finding a distribution continuous with the log-normal distribution previously found for solar-type stars at longer periods, but with a significant steepening at P_(orb) ≲ 3 days, and a pile-up of contact binaries at P_(orb) ≈ 0.4 days. Companions in the period range 1--5 days are found to be an order of magnitude more frequent around stars hotter than ≈6250K (the Kraft break) when compared to cooler stars, suggesting that magnetic braking plays an important role in shaping the temperature and period distributions. We detect resolved tertiary companions to 9.0 ± 0.2 per cent of our binaries with a median separation of 3200 AU. The frequency of tertiary companions rises to 29 ± 5 per cent among the systems with the shortest ellipsoidal periods. This large binary sample with quantified selection effects will be a powerful resource for future studies of detached and contact binary systems with P_(orb) < 5 days.

Additional Information

This work was supported by the European Research Council (ERC) under the European Union's FP7 Programme, Grant No. 833031 (DM). We further acknowledge support by a grant from the GIF–the German Israeli Foundation for Science and Development (DM, TM, HWR). This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA's Science Mission Directorate. This work makes use of observations from the Las Cumbres Observatory global telescope network. This work made use of the software packages beer, python, numpy, scipy, astropy, matplotlib, eleanor (Feinstein et al. 2019), sparta (Shahaf et al. 2020), ellc (Maxted 2016), phoebe (Prsa & Zwitter 2005; Prša et al. 2016), and saphires. DATA AVAILABILITY, In the online material can be found the complete versions of Tables 2, 3, and A1, giving details on the scores assigned to every TESS lightcurve analysed, the selected sample, and the subset of targets followed up using LCOGT. TESS full-frame images are available from the Barbara A. Mikulski Archive for Space Telescopes (MAST),10 as are the QLP extracted lightcurves used in the northern hemisphere. LCOGT data are available via the LCOGT data archive. Any other data can be made available upon reasonable request to the authors.

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Additional details

Created:
August 20, 2023
Modified:
October 24, 2023