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Microlensing Events in the Galactic Plane Using the Zwicky Transient Facility

Rodriguez, Antonio C. and Mróz, Przemek and Kulkarni, Shrinivas R. and Andreoni, Igor and Bellm, Eric C. and Dekany, Richard and Drake, Andrew J. and Duev, Dmitry A. and Graham, Matthew J. and Masci, Frank J. and Prince, Thomas A. and Riddle, Reed and Shupe, David L. (2022) Microlensing Events in the Galactic Plane Using the Zwicky Transient Facility. Astrophysical Journal, 927 (2). Art. No. 150. ISSN 0004-637X. doi:10.3847/1538-4357/ac51cc.

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Microlensing is a powerful technique to study the Galactic population of "dark" objects such as exoplanets both bound and unbound, brown dwarfs, low-luminosity stars, old white dwarfs, and neutron stars, and it is almost the only way to study isolated stellar-mass black holes. The majority of previous efforts to search for gravitational microlensing events have concentrated toward high-density fields such as the Galactic bulge. Microlensing events in the Galactic plane have the advantage of closer proximity and better constrained relative proper motions, leading to better constrained estimates of lens mass at the expense of a lower optical depth, than events toward the Galactic bulge. We use the Zwicky Transient Facility Data Release 5 compiled from 2018–2021 to survey the Galactic plane in the region of ∣b∣ < 20°. We find a total of 60 candidate microlensing events including three that show a strong microlensing parallax effect. The rate of events traces Galactic structure, decreasing exponentially as a function Galactic longitude with scale length ℓ₀ ∼ 37°. On average, we find Einstein timescales of our microlensing events to be about three times as long (∼60 days) as those toward the Galactic bulge (∼20 days). This pilot project demonstrates that microlensing toward the Galactic plane shows strong promise for characterization of dark objects within the Galactic disk.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Rodriguez, Antonio C.0000-0003-4189-9668
Mróz, Przemek0000-0001-7016-1692
Kulkarni, Shrinivas R.0000-0001-5390-8563
Andreoni, Igor0000-0002-8977-1498
Bellm, Eric C.0000-0001-8018-5348
Dekany, Richard0000-0002-5884-7867
Duev, Dmitry A.0000-0001-5060-8733
Graham, Matthew J.0000-0002-3168-0139
Masci, Frank J.0000-0002-8532-9395
Prince, Thomas A.0000-0002-8850-3627
Riddle, Reed0000-0002-0387-370X
Shupe, David L.0000-0003-4401-0430
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 December 14; revised 2022 January 16; accepted 2022 February 2; published 2022 March 11. The authors thank the ZTF Variable Star Group for insightful discussions. A.C.R. acknowledges funding support from the Caltech Anthony Fellowship through the Division of Physics, Mathematics, and Astronomy. This work is based on observations obtained with the Samuel Oschin Telescope 48 inch and the 60 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. Major funding has been provided by the US National Science Foundation under grant No. AST-1440341 and by the ZTF partner institutions: the California Institute of Technology, the Oskar Klein Centre, the Weizmann Institute of Science, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron, the University of Wisconsin-Milwaukee, and the TANGO Program of the University System of Taiwan. The ZTF forced-photometry service was funded under the Heising–Simons Foundation grant #12540303 (PI: Graham). This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular, the institutions participating in the Gaia Multilateral Agreement.
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility
Funding AgencyGrant Number
Earle C. Anthony FellowshipUNSPECIFIED
ZTF partner institutionsUNSPECIFIED
Heising-Simons Foundation12540303
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:Gravitational microlensing; Stellar remnants; Microlensing parallax; Time domain astronomy
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Gravitational microlensing (672); Stellar remnants (1627); Microlensing parallax (2144); Time domain astronomy (2109)
Record Number:CaltechAUTHORS:20220113-234555128
Persistent URL:
Official Citation:Antonio C. Rodriguez et al 2022 ApJ 927 150
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112902
Deposited By: George Porter
Deposited On:14 Jan 2022 19:15
Last Modified:14 Mar 2022 20:58

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