TESSILATOR: a one-stop shop for measuring TESS rotation periods

ABSTRACT We present a software package designed to produce photometric light curves and measure rotation periods from full-frame images taken by the Transiting Exoplanet Survey Satellite (TESS), which we name ‘tessilator’. tessilator is the only publicly available code that will run a full light curve and rotation period (P ₑ₎ₓ) analysis based on just a (list of) target identifier (s) or sky position (s) via a simple command-line prompt. This paper sets out to introduce the rationale for developing tessilator, and then describes the methods, considerations, and assumptions for: extracting photometry; dealing with potential contamination; accounting for natural and instrumental systematic effects; light-curve normalization and detrending; removing outliers and unreliable data; and finally, measuring the P ₑ₎ₓ value and several periodogram attributes. Our methods have been tuned specifically to optimize TESS light curves and are independent from the pipelines developed by the TESS Science Processing Operations Center (SPOC), meaning tessilator can, in principle, analyse any target across the entire celestial sphere. We compare tessilatorP ₑ₎ₓ measurements with TESS-SPOC-derived light curves of 1560 (mainly solar-type and low-mass) stars across four benchmark open clusters (Pisces–Eridanus, the Pleiades, the Hyades, and Praesepe) and a sample of nearby field M-dwarfs. From a vetted subsample of 864 targets we find an excellent return of P ₑ₎ₓ matches for the first three open clusters (85 per cent) and a moderate (60 per cent) match for the 700 Myr Praesepe and MEarth sample, which validates tessilator as a tool for measuring P ₑ₎ₓ. The tessilator code is available at https: //github. com/alexbinks/tessilator.