KMT-2025-BLG-1616Lb: First Microlensing Bound Planet From DREAMS

TL;DR

This paper reports the first microlensing bound planet detection from DREAMS, demonstrating DREAMS's capability to resolve degeneracies and detect low-mass planets, including potential free-floating planets, in the Galactic bulge and disk.

Contribution

It presents the first bound planet detection using DREAMS data, showcasing its high-cadence observations for breaking degeneracies and detecting low-mass planets.

Findings

DREAMS successfully broke the central/resonant degeneracy in the binary-lens model.

The planetary system has a host mass of ~0.3 M_sun and a planet mass of ~40 M_earth.

DREAMS is sensitive to Mars-mass free-floating planets in the Galactic bulge.

Abstract

We present observations and analysis of the bound planetary microlensing event KMT-2025-BLG-1616. The planetary signal was captured by the Korea Microlensing Telescope Network (KMTNet) and the DECam Rogue Earths and Mars Survey (DREAMS). DREAMS's minute-cadence observations break the central/resonant degeneracy in the binary-lens models. The color of the faint source star ($I=22$) is measured from the DREAMS's $r - z$ color. The planetary system has a planet-host mass ratio of $q \sim 5 \times 10^{-4}$. A Bayesian analysis yields a host-star mass of $\sim 0.3\,M_\odot$, a planetary mass of $\sim 40\,M_{\oplus}$, a projected planet-host separation of $\sim 1.6~\mathrm{au}$, and a lens distance of $\sim 7.5~\mathrm{kpc}$. Based on the photometric precision achieved by DREAMS for this event, we simulate free-floating planet (FFP) detections and find that DREAMS is sensitive to Mars-mass FFPs in the Galactic bulge and Moon-mass FFPs in the Galactic disk.