False-positive Self-lensing Events: TESS Observing Asteroid-crossing Events in Disguise

Abstract

We report observations of four asteroid-crossing events in Transiting Exoplanet Survey Satellite light curves masquerading as self-lensing pulses from binary systems containing main-sequence stars and black hole or neutron-star companions. The observed changes in flux and the durations of the events appear to be consistent with self-lensing pulses provided that (a) the compact-object mass is greater than 2 solar masses, and (b) the transit is not a perfect alignment, i.e., the center of the lens is not passing directly in front of the center of the source. We examine the relationship between the physical characteristics of these asteroid crossings and the derived parameters of our self-lensing model fits to the data sets. As the search for new self-lensing systems continues, we caution observers about such false-positive signals imitating real self-lensing pulses.

Keywords

• Asteroids
• Compact binary stars
• Gravitational microlensing