2020/04/30 by Przemek Mróz, Przemek Mroz, Andrzej Udalski +16 · 30 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Bulge #Galactic corona #Galactic halo #Galactic plane #Galactic tide #Gravitational lens #Gravitational microlensing #Milky Way #Pulsars and Gravitational Waves Research #Stellar, planetary, and galactic studies #astro-ph.GA #astro-ph.IM #astro-ph.SR
paper · pdf · doi:10.3847/1538-4365/ab9366
published in The Astrophysical Journal Supplement Series 249(1), 16 (Institute of Physics) · ApJS, in press
openalex created_date 2020/04/24 · arxiv created 2020/06/12 · openalex publication_date 2020/07/01 · arxiv updated 2020/07/20 · openalex updated_date 2026/08/05
Abstract Searches for gravitational microlensing events are traditionally concentrated on the central regions of the Galactic bulge but many microlensing events are expected to occur in the Galactic plane, far from the Galactic Center. Owing to the difficulty in conducting high-cadence observations of the Galactic plane over its vast area, which are necessary for the detection of microlensing events, their global properties were hitherto unknown. Here, we present results of the first comprehensive search for microlensing events in the Galactic plane. We searched an area of almost 3000 square degrees along the Galactic plane ( , 0° < l < 50°, 190° < l < 360°) observed by the Optical Gravitational Lensing Experiment (OGLE) during 2013–2019 and detected 630 events. We demonstrate that the mean Einstein timescales of Galactic plane microlensing events are on average three times longer than those of Galactic bulge events, with little dependence on the Galactic longitude. We also measure the microlensing optical depth and event rate as a function of Galactic longitude and demonstrate that they exponentially decrease with the angular distance from the Galactic Center (with the characteristic angular scale length of 32°). The average optical depth decreases from 0.5 × 10 −6 at l = 10° to 1.5 × 10 −8 in the Galactic anticenter. We also find that the optical depth in the longitude range 240° < l < 330° is asymmetric about the Galactic equator, which we interpret as a signature of the Galactic warp.