TESS Data for Asteroseismology: Timing Verification^*

Abstract

The Transiting Exoplanet Survey Satellite (TESS) is NASA's latest space telescope dedicated to the discovery of transiting exoplanets around nearby stars. Besides the main goal of the mission, asteroseismology is an important secondary goal and very relevant for the high-quality time series that TESS will make during its two year all-sky survey. Using TESS for asteroseismology introduces strong timing requirements, especially for coherent oscillators. Although the internal clock on board TESS is precise in its own time, it might have a constant drift and will thus need calibration, or offsets might inadvertently be introduced. Here we present simultaneously ground-and space-based observations of primary eclipses of several binary systems in the Southern ecliptic hemisphere, used to verify the reliability of the TESS timestamps. From twelve contemporaneous TESS/ground observations we determined a time offset equal to 5.8 ± 2.5 sec, in the sense that the Barycentric time measured by TESS is ahead of real time. The offset is consistent with zero at 2.3 − σ level. In addition, we used 405 individually measured mid-eclipse times of 26 eclipsing binary stars observed solely by TESS to test the existence of a potential drift with a monotonic growth (or decay) affecting the observations of all stars. We find a drift corresponding to σ drift = 0.009 ± 0.015 sec/day. We find that the measured offset is of a size that will not become an issue for comparing ground-based and space data for coherent oscillations for most of the targets observed with TESS.

Characterizing the WASP-4 System with TESS and Radial Velocity Data: Constraints on the Cause of the Hot Jupiter’s Changing Orbit and Evidence of an Outer Planet

“…Motivated by the possible changing period of WASP-4b, we analyze all three sectors (Figure 1) from TESS and combine the results with all transit, occultation, and RV measurements from the literature to verify its changing period and derive updated planetary properties. TESS is well suited for our study because it provides high-precision time-series data, ideal for searching for TTVs (e.g., Hadden et al 2019;Pearson 2019;von Essen et al 2020;Ridden-Harper et al 2020;Turner et al 2021). Altogether, the transit data span 13 yr from 2007-2020 and the RV data span 12 yr from 2007-2019.…”

TESS search for substellar companions through pulsation timing of δ Scuti stars

“…While some of the reported offsets have been already corrected in subsequent update data releases, others are still waiting to be implemented. A groundbased campaign by von Essen et al (2020) tried to independently confirm the absolute time calibration of TESS by comparing observations of a sample of eclipsing binaries in common, measuring a global offset of 5.8±2.5 s; the errors of the measurements at individual epochs, however, are too large ( 10 s) to confirm or disprove the systematic errors we see. We emphasize that offsets of a few seconds are usually completely negligible when investigating transiting exoplanets, but they are crucial in extending the sensitivity of the PT technique to planet-mass companions.…”

Space-Based Photometry of Binary Stars: From Voyager to TESS

“…EBs can, in turn, be used as an independent check on the timestamps from space satellites (Von Essen et al [37]).…”