Gaia-GIC-1: An Evolving Catastrophic Planetesimal Collision Candidate

TL;DR

Gaia-GIC-1 is a young star exhibiting irregular optical dimming and infrared brightening, likely caused by debris from recent planetary collisions, offering insights into terrestrial planet formation processes.

Contribution

This study reports the discovery and characterization of Gaia-GIC-1, a system showing evidence of recent planetary collision debris with unique variability patterns.

Findings

Detected a 380.5-day periodic modulation in Gaia-G band.

Infrared brightening has persisted for over 4 years.

Dust temperature estimated at approximately 900 Kelvin.

Abstract

We report the discovery of the optical dipper and low-luminosity infrared stellar transient Gaia20ehk (hereafter, Gaia-GIC-1), which is currently undergoing high-amplitude variability due to transiting dusty material. In this work, we identify Gaia-GIC-1 as a likely young F-type star based on the spectral energy distribution before the onset of the high-amplitude optical variability. We detect a significant periodic modulation of 380.5 days in Gaia-G band before the onset of the infrared brightening, consistent with a $\sim$1.1 AU orbit assuming circular orbits and a 1.3 M$_{\odot}$ star. The system has remained in an infrared bright state for $>$4 years since the last near-infrared detection, confirmed by recent SPHEREx observations, while continuing to undergo large amplitude irregular optical dimming. We measure the dust temperature from the freshly generated debris to be $\sim$900 Kelvin based on available WISE photometry, and the dust clump size to have a minimum cross-sectional area of 0.13 AU$^{2}$, and the dust mass $4\times 10^{20}$ kg. Currently, optical follow-up spectroscopy has not revealed any prominent features in the system, likely due to its highly variable nature. We hypothesize that Gaia-GIC-1 represents debris recently formed in a planetary collision, which produced a clumpy dust cloud on a bound orbit, producing the observed dimming events. The ongoing collisional activity in this system presents a unique opportunity for understanding terrestrial planet formation.