Quantifying the Contamination of TESS Ecliptic-Plane Light Curves by Minor Planets

TL;DR

This study quantifies how minor planets contaminate TESS ecliptic-plane light curves, showing that most targets are affected by close flybys, which can significantly alter observed brightness measurements.

Contribution

The paper provides a comprehensive analysis of minor planet contamination in TESS data using N-body simulations and mock photometry, a novel approach for assessing solar system object impacts.

Findings

Over 95% of high-cadence targets have a minor planet pass within 1 pixel.

50% of targets brighter than magnitude 13 experience flux contamination exceeding 1%.

Contamination effects are common and can significantly influence light curve analysis.

Abstract

Though missions devoted to time series photometry focus primarily on targets far beyond the solar system, their observations can be contaminated by foreground minor planets, especially near the ecliptic plane where solar system objects are most prevalent. Crucially, depending on one's choice of data reduction/background estimation algorithm, these objects can induce both apparent brightening and/or dimming events in processed light curves. To quantify the impact of these objects on archived TESS light curves, we used N-body integrations of all currently known minor planets to postdict all 600,000+ of their interactions with stars selected for high-cadence observations during TESS ecliptic plane sectors. We then created mock images of these moving sources and performed simple aperture photometry using the same target and background apertures used in SPOC processing. Our resulting 10,000+ target-specific light curves, which faithfully model the time-dependent positions and magnitudes of the actual solar system objects that approached each target, reveal that $>95\%$ of high-cadence ecliptic plane targets experience a minor planet crossing within 1 TESS pixel of the source. Additionally, 50% of all $T>13$ mag targets experience at least one instantaneous moment where the contaminating flux from minor planets exceeds 1% of the target flux. We discuss these population-level results and others, and highlight several case studies of bright flybys.