Static Microlensing: Concept, Method and Candidates

TL;DR

This paper introduces a static microlensing detection method that identifies microlensing events by analyzing luminosity outliers among stars with similar spectral energy distributions, using archival data instead of time monitoring.

Contribution

It presents a novel static microlensing approach based on spectral similarity and outlier detection, enabling the discovery of candidates from existing survey archives.

Findings

Identified 5 microlensing candidates in the Galactic halo.

Demonstrated the feasibility of static microlensing using Gaia and SDSS data.

Proposed a new method that complements traditional time domain searches.

Abstract

We propose a novel microlensing event search method that differs from either the traditional time domain method, astrometric microlensing, or the parallax microlensing method. Our method assumes that stars with nearly identical "genes" - normalized Spectral Energy Distributions (SED) bear the same luminosity within the intrinsic scatter due to stellar properties. Given a sample of stars with similar normalized SEDs, the outliers in luminosity distribution can be considered microlensing events by excluding other possible variations. In this case, we can select microlensing events from archive data rather than time domain monitoring the sky, which we describe as static microlensing. Following this concept, we collect the data from Gaia DR3 and SDSS DR16 from the northern galactic cap at high galactic latitudes. This area is not preferable for normal microlensing search due to the low stellar density and, therefore, low discovery rate. By applying a similarity search algorithm, we find 5 microlensing candidates in the Galactic halo.