Casting Light on Degeneracies: A Comprehensive Study of Lightcurve Variations in Microlensing Events OGLE-2017-BLG-0103 and OGLE-2017-BLG-0192

TL;DR

This paper explores degeneracies in lightcurve variations of microlensing events OGLE-2017-BLG-0103 and OGLE-2017-BLG-0192, revealing multiple solutions and emphasizing the importance of high-resolution follow-up observations for accurate lens characterization.

Contribution

It provides a comprehensive analysis of parallax degeneracies in specific microlensing events, introducing new degenerate solutions and highlighting the role of xallarap effects in modeling.

Findings

Four discrete parallax solutions for OGLE-2017-BLG-0103.

No degeneracy in OGLE-2017-BLG-0192 solutions.

Future AO observations can confirm lens properties.

Abstract

This study investigates orbital parallax in gravitational microlensing events, focusing on OGLE-2017-BLG-0103 and OGLE-2017-BLG-0192. For events with timescales $\leq$ 60 days, a Jerk Parallax degeneracy arises due to high Jerk velocity ($\tilde{v_{j}}$), causing a four-fold continuous parallax degeneracy. OGLE-2017-BLG-0103, after incorporating orbital parallax, reveals four discrete degenerate parallax solutions, while OGLE-2017-BLG-0192 exhibits four discrete solutions without degeneracy. {The asymmetric light curve of OGLE-2017-BLG-0103 suggests a more probable model where xallarap is added to the parallax model, introducing tension. The galactic model analysis predicts a very low mass stellar lens for OGLE-2017-BLG-0192. For OGLE-2017-BLG-0103, degenerate solutions suggest a low-mass star or a darker lens in the disc, while the Xallarap+Parallax model also predicts a stellar lens in the bulge, with the source being a solar-type star orbited by a dwarf star.} This study presents five degenerate solutions for OGLE-2017-BLG-0103, emphasizing the potential for confirmation through high-resolution Adaptive Optics (AO) observations with Extremely Large Telescopes in the future. The complexities of degenerate scenarios in these microlensing events underscore the need to analyze special single-lens events in the Roman Telescope Era.