Distant trans-Neptunian object candidates from NASA's TESS mission scrutinized: fainter than predicted or false positives?

TL;DR

This study used ground-based telescopes to follow up on TESS-identified distant Solar system object candidates, finding they are likely fainter than expected or false positives, highlighting challenges in confirming such distant objects.

Contribution

First ground-based follow-up attempt on TESS-detected distant Solar system candidates, revealing potential overestimation of their brightness or false detection rates.

Findings

Candidates are fainter than predicted or false positives.

Ground-based observations did not confirm the candidates.

Highlights need for improved detection and confirmation methods.

Abstract

NASA's Transiting Exoplanet Survey Satellite (TESS) is performing a homogeneous survey of the sky from space in search of transiting exoplanets. The collected data are also being used for detecting passing Solar system objects, including 17 new outer Solar system body candidates located at geocentric distances in the range 80-200 au, that need follow-up observations with ground-based telescope resources for confirmation. Here, we present results of a proof-of-concept mini-survey aimed at recovering two of these candidates that was carried out with the 4.2 m William Herschel Telescope and a QHY600L CMOS camera mounted at its prime focus. For each candidate attempted, we surveyed a patch of sky of over one square degree around its expected coordinates in Sloan r'. The same location was revisited in five consecutive or nearly consecutive nights, reaching S/N > 4 at r' < 23 mag. We focused on the areas of sky around the circumpolar TESS candidates located at equatorial coordinates (07:00:15, +86:55:19), 202.8 au from Earth, and (06:39:47, +83:43:54) at 162.1 au, but we could not recover either of them at r' < 23 mag. Based on the detailed analysis of the acquired images, we confirm that either both candidates are much fainter than predicted or that they are false positives.