Geosynchronous Microlens Parallaxes

Abstract

I show that for a substantial fraction of planets detected in a space-based survey, it would be possible to measure the planet and host masses and distances, if the survey satellite were placed in geosynchronous orbit. Such an orbit would enable measurement of the microlens parallax, π_e, for events with moderately low impact parameters, β<~ 0.05, which encompass a disproportionate share of planetary detections. Most planetary events yield a measurement of the angular Einstein radius θ_e. Since the host mass is given by M=θ_e/κπ_e where κ is a constant, parallax measurements are the crucial missing link. I present simple analytic formulae that enable quick error estimates for observatories in circular orbits of arbitrary period and semi-major axis, and arbitrary orientation relative to the line of sight. The method requires photometric stability of ~1e-4 on ~1 orbit timescales. I show that the satellite data themselves can provide a rigorous test of the accuracy of the parallax measurements in the face of unknown systematics and stellar variability, even at this extreme level.

12 pages including 3 figures, ApJL in press

References in corpus (4)

• Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. V. Evidence for a wide age distribution and a complex MDF
• Identification of the OGLE-2003-BLG-235/MOA-2003-BLG-53 Planetary Host Star
• Cheap Space-Based Microlens Parallaxes for High-Magnification Events
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Cited by in corpus (18)

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• Campaign 9 of the $K2$ Mission: Observational Parameters, Scientific Drivers, and Community Involvement for a Simultaneous Space- and Ground-based Microlensing Survey
• Microlens Masses From Astrometry and Parallax in Space-Based Surveys: From Planets to Black Holes
• Mass Measurements of Isolated Objects from Space-based Microlensing
• Gas Giants in Hot Water: Inhibiting Giant Planet Formation and Planet Habitability in Dense Star Clusters Through Cosmic Time
• Spitzer as Microlens Parallax Satellite: Mass and Distance Measurements of Binary Lens System OGLE-2014-BLG-1050L
• WFIRST Planet Masses from Microlens Parallax
• First simultaneous microlensing observations by two space telescopes: $Spitzer$ & $Swift$ reveal a brown dwarf in event OGLE-2015-BLG-1319
• WFIRST and EUCLID: enabling the microlensing parallax measurement from space
• A Reanalysis of Public Galactic Bulge Gravitational Microlensing Events from OGLE-III and IV
• Microlensing Parallax for Observers in Heliocentric Motion
• OGLE-2015-BLG-1670Lb: A Cold Neptune beyond the Snow Line in the Provisional WFIRST Microlensing Survey Field
• Microlensing planet detection via geosynchronous and low Earth orbit satellites
• Spitzer Microlensing of MOA-2016-BLG-231L : A Counter-Rotating Brown Dwarf Binary in the Galactic Disk
• Disentangling the Black Hole Mass Spectrum with Photometric Microlensing Surveys
• Revealing Short-period Exoplanets and Brown Dwarfs in the Galactic Bulge using the Microlensing Xallarap Effect with the \textit{Nancy Grace Roman Space Telescope}
• Measuring the microlensing parallax from various space observatories
• The impact of the free-floating planet (FFP) mass function on the event rate for the accurate microlensing parallax determination: application to Euclid and Roman parallax observation