Historical Surveys to Rubin First Look: Absolute Colors of Trans-Neptunian Objects

Abstract We present a comprehensive photometric study of trans-Neptunian objects (TNOs) by combining data from the Sloan Digital Sky Survey, the Colours of the Outer Solar System Origins Survey, the Dark Energy Survey, and the recent Rubin First Look (RFL) data. Our database comprises 43,677 measurements in the u , g , r , i , and z bands, from which we derived 2177 phase curves for 776 unique objects. From these data, we computed 2524 absolute color measurements for 627 objects, enabling a statistical characterization of phase-coloring effects. Our results show correlations between colors at opposition and their variation with phase angle, indicating that redder (bluer) objects tend to become redder (bluer) as the phase angle increases. With a larger sample and the application of phase corrections, the colors show no strong bimodality or correlation with orbital parameters. Notably, our dataset includes the first photometric measurements from Rubin Observatory during RFL, covering eight objects—five newly discovered TNOs and three previously known. These early LSST observations occupy sparsely sampled regions of parameter space, particularly at faint magnitudes, highlighting the discovery and characterization potential of the full survey.