Journal article
Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. IV. Lens Mass and Distance Measurements
The Astronomical journal, Vol.171(4), 212
04/01/2026
DOI: 10.3847/1538-3881/ae43e6
Abstract
As part of the Galactic Bulge Time Domain Survey (GBTDS), the Nancy Grace Roman Galactic Exoplanet Survey (RGES) will use microlensing to discover cold outer planets and free-floating planets not bound to stars. NASA has established several science requirements for the GBTDS to ensure RGES success. A key advantage of RGES is Roman’s high angular resolution, which will allow detection of flux from many host stars. One requirement specifies that Roman must measure the masses and distances of 40% of detected planet hosts with 20% precision or better. To test this, we simulated microlensing events toward the GBTDS fields and used Fisher matrix analysis to estimate light curve parameter uncertainties. Combining these with Roman imaging observables (lens flux and relative lens–source proper motion), we estimated the achievable precision of lens mass and distance measurements. Using pyLIMASS, a publicly available code for estimating lens properties, we applied this analysis to 3000 simulated events. Assuming the A. Cassan et al. exoplanet mass function, we find that ≥40% of host stars meet the required 20% precision threshold, confirming that the GBTDS can satisfy the mission requirement. We validated our approach by comparing our inferred lens masses and distances to empirical measurements from detailed image-constrained light curve modeling of historical microlensing events with Hubble and Keck follow-up imaging. Our results agree within roughly 1σ, demonstrating that both approaches yield consistent and reliable mass and distance estimates, and confirming the robustness of our simulations for Roman-era microlensing science.
Details
- Title: Subtitle
- Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. IV. Lens Mass and Distance Measurements
- Creators
- Sean K Terry - Goddard Space Flight CenterEtienne Bachelet - Centre National de la Recherche ScientifiqueFarzaneh Zohrabi - Louisiana State UniversityHimanshu Verma - Louisiana State UniversityAlison Crisp - The Ohio State UniversityMacy J Huston - University of California, BerkeleyCarissma McGee - American Institute of Aeronautics and AstronauticsMatthew Penny - Louisiana State UniversityNatasha S Abrams - University of California, BerkeleyMichael D Albrow - University of CanterburyJay Anderson - Space Telescope Science InstituteFatemeh Bagheri - Goddard Space Flight CenterJean-Philippe Beaulieu - Centre National de la Recherche ScientifiqueAndrea Bellini - Space Telescope Science InstituteDavid P Bennett - Goddard Space Flight CenterGalen Bergsten - Space Telescope Science InstituteT. Dex Bhadra - Goddard Space Flight CenterAparna Bhattacharya - Goddard Space Flight CenterIan A Bond - Massey UniversityValerio Bozza - University of SalernoChristopher Brandon - The Ohio State UniversitySebastiano Calchi Novati - California Institute of TechnologySean Carey - California Institute of TechnologyJessie Christiansen - California Institute of TechnologyWilliam DeRocco - Johns Hopkins UniversityB. Scott Gaudi - The Ohio State UniversityJon Hulberg - Goddard Space Flight CenterStela Ishitani SilvaSinclaire E Jones - The Ohio State UniversityEamonn Kerins - University of ManchesterSomayeh Khakpash - Lehigh UniversityKatarzyna Kruszyńska - Las Cumbres Observatory Global Telescope NetworkCasey Lam - Carnegie Institution for ScienceJessica R Lu - University of California, BerkeleyAmber Malpas - The Ohio State UniversityShota Miyazaki - Japan Aerospace Exploration AgencyPrzemek Mróz - University of WarsawArjun Murlidhar - The Ohio State UniversityDavid Nataf - University of IowaMarz Newman - Louisiana State UniversityGreg Olmschenk - Goddard Space Flight CenterRadek Poleski - University of WarsawClément Ranc - Centre National de la Recherche ScientifiqueNicholas J Rattenbury - University of AucklandKrzysztof Rybicki - University of WarsawVito Saggese - Istituto Nazionale di Fisica Nucleare, Sezione di NapoliJennifer Sobeck - California Institute of TechnologyKeivan G Stassun - Vanderbilt UniversityAlexander P Stephan - Vanderbilt UniversityRachel A Street - Las Cumbres Observatory Global Telescope NetworkTakahiro Sumi - Osaka Health Science UniversityDaisuke Suzuki - Osaka Health Science UniversityAikaterini Vandorou - Goddard Space Flight CenterMeet Vyas - Ahmedabad UniversityJennifer C YeeWeicheng Zang - Center for Astrophysics Harvard & SmithsonianKeming Zhang - Kavli Institute for Particle Astrophysics and Cosmology(Roman Galactic Exoplanet Survey Project Infrastructure Team) (Roman Galactic Exoplanet Survey Project Infrastructure Team)
- Resource Type
- Journal article
- Publication Details
- The Astronomical journal, Vol.171(4), 212
- DOI
- 10.3847/1538-3881/ae43e6
- ISSN
- 1538-3881
- eISSN
- 1538-3881
- Publisher
- IOP Publishing
- Grant note
- National Aeronautics and Space Administration (NASA): 80NSSC24M0022
Funding for the Roman Galactic Exoplanet Survey Project Infrastructure Team is provided by the Nancy Grace Roman Space Telescope Project through the National Aeronautics and Space Administration grant 80NSSC24M0022, by The Ohio State University through the Thomas Jefferson Chair for Space Exploration endowment, and by the Vanderbilt Initiative in Data-intensive Astrophysics (VIDA). J.P.B. has been supported by the Australian Government through the Australian Research Council Discovery Project grant 240101842. J.P.B. is supported by the SPACE-MLENS ANR grant ANR-24-CE31-3263. M.J.H. Acknowledges support from the Heising-Simons Foundation under grant No. 2022-3542.
- Language
- English
- Date published
- 04/01/2026
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9985143133502771
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