An Earth-mass Planet in a Time of Covid-19: KMT-2020-BLG-0414Lb

Abstract

We report the discovery of KMT-2020-BLG-0414Lb, with a planet-to-host mass ratio $q_2=0.9$--$1.2\times 10^{-5}=3$--$4q_{\oplus }$ at $1\sigma$, which is the lowest mass-ratio microlensing planet to date. Together with two other recent discoveries ($4\lesssim q/q_{\oplus }\lesssim 6$), it fills out the previous empty sector at the bottom of the triangular $(\log s,\log q)$ diagram, where $s$ is the planet-host separation in units of the angular Einstein radius ${\theta }_{\mathrm{E}}$. Hence, these discoveries call into question the existence, or at least the strength, of the break in the mass-ratio function that was previously suggested to account for the paucity of very low-$q$ planets. Due to the extreme magnification of the event, $A_{\max }\sim 1450$ for the underlying single-lens event, its light curve revealed a second companion with $q_3\sim 0.05$ and $|\log s_3|\sim 1$, i.e., a factor $\sim 10$ closer to or farther from the host in projection. The measurements of the microlens parallax ${\pi }_{\mathrm{E}}$ and the angular Einstein radius ${\theta }_{\mathrm{E}}$ allow estimates of the host, planet, and second companion masses, $(M_1,M_2,M_3)\sim (0.3M_{\odot },1.0M_{\oplus },17M_J)$, the planet and second companion projected separations, $(a_{\perp ,2},a_{\perp ,3})\sim (1.5,0.15\mathrm{or}15)$~au, and system distance $D_{\mathrm{L}}\sim 1$ kpc. The lens could account for most or all of the blended light ($I\sim 19.3$) and so can be studied immediately with high-resolution photometric and spectroscopic observations that can further clarify the nature of the system. The planet was found as part of a new program of high-cadence follow-up observations of high-magnification events. The detection of this planet, despite the considerable difficulties imposed by Covid-19 (two KMT sites and OGLE were shut down), illustrates the potential utility of this program.

arXiv comment23 pages, 5 figures; to be submitted to RAA

References in corpus (64)

• emcee: The MCMC Hammer
• Galactic Stellar and Substellar Initial Mass Function
• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• A method for optimal image subtraction
• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• Reddening and Extinction Toward the Galactic Bulge from OGLE-III: The Inner Milky Way's Rv ~ 2.5 Extinction Curve
• Real-Time Difference Imaging Analysis of MOA Galactic Bulge Observations During 2000
• 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
• OGLE-2003-BLG-262: Finite-Source Effects from a Point-Mass Lens
• The Use of High Magnification Microlensing Events in Discovering Extra-solar Planets
• Discovery of a Jupiter/Saturn Analog with Gravitational Microlensing
• Frequency of Solar-Like Systems and of Ice and Gas Giants Beyond the Snow Line from High-Magnification Microlensing Events in 2005-2008
• The Exoplanet Mass-Ratio Function from the MOA-II Survey: Discovery of a Break and Likely Peak at a Neptune Mass
• Expanding the Realm of Microlensing Surveys with Difference Image Photometry
• A Natural Formalism for Microlensing
• Difference imaging photometry of blended gravitational microlensing events with a numerical kernel
• Resolution of the MACHO-LMC-5 Puzzle: The Jerk-Parallax Microlens Degeneracy
• MOA-2011-BLG-293Lb: A test of pure survey microlensing planet detections
• OGLE-2005-BLG-071Lb, the Most Massive M-Dwarf Planetary Companion?
• Binary microlensing event OGLE-2009-BLG-020 gives a verifiable mass, distance and orbit predictions
• MOA-2009-BLG-387Lb: A massive planet orbiting an M dwarf
• A Sub-Earth-Mass Moon Orbiting a Gas Giant Primary or a High Velocity Planetary System in the Galactic Bulge
• Planetary Detection Efficiency of the Magnification 3000 Microlensing Event OGLE-2004-BLG-343
• Masses and Orbital Constraints for the OGLE-2006-BLG-109Lb,c Jupiter/Saturn Analog Planetary System
• Finite Source Sizes and the Information Content of MACHO-Type Lens Search Light Curves
• Systematic Analysis of 22 Microlensing Parallax Candidates
• Identification of the OGLE-2003-BLG-235/MOA-2003-BLG-53 Planetary Host Star
• Microlensing with advanced contour integration algorithm: Green's theorem to third order, error control, optimal sampling and limb darkening
• Microlensing Constraints on the Frequency of Jupiter-Mass Companions: Analysis of Five Years of PLANET Photometry
• Microlensing by Multiple Planets in High Magnification Events
• A Terrestrial Planet in a ~1 AU Orbit Around One Member of a ~15 AU Binary
• On Planetary Companions to the MACHO-98-BLG-35 Microlens Star
• VBBinaryLensing: a public package for microlensing light curve computation
• Toward a Galactic Distribution of Planets. I. Methodology & Planet Sensitivities of the 2015 High-Cadence Spitzer Microlens Sample
• The second multiple-planet system discovered by microlensing: OGLE-2012-BLG-0026Lb, c, a pair of jovian planets beyond the snow line
• OGLE-2003-BLG-238: Microlensing Mass Estimate of an Isolated Star
• Extreme Magnification Microlensing Event OGLE-2008-BLG-279: Strong Limits on Planetary Companions to the Lens Star
• Predictions for Microlensing Planetary Events from Core Accretion Theory
• Einstein Radii from Binary Lensing Events
• Revisiting the microlensing event OGLE 2012-BLG-0026: A solar mass star with two cold giant planets
• WFIRST Exoplanet Mass Measurement Method Finds a Planetary Mass of $39\pm 8M_{\oplus }$ for OGLE-2012-BLG-0950Lb
• Predicting Stellar Angular Diameters from $V$, $I_C$, $H$, $K$ Photometry
• MOA 2003-BLG-37: A Bulge Jerk-Parallax Microlens Degeneracy
• The First Neptune Analog or Super-Earth with Neptune-like Orbit: MOA-2013-BLG-605Lb
• OGLE-2016-BLG-0613LABb: A Microlensing Planet in a Binary System
• KMT-2017-BLG-0165Lb: A Super-Neptune mass planet Orbiting a Sun-like Host Star
• Analysis of Microlensing Light Curves Induced by Multiple-Planet Systems
• OGLE-2017-BLG-0173Lb: Low Mass-Ratio Planet in a "Hollywood" Microlensing Event
• The first direct detection of a gravitational micro-lens toward the Galactic bulge
• OGLE-2018-BLG-1011L\lowercase{b,c}: Microlensing Planetary System with Two Giant Planets Orbiting a Low-mass Star
• Empirical Study of Simulated Two-planet Microlensing Event
• Measurement of Source Star Colors with the K2C9-CFHT Multi-color Microlensing Survey
• A Likely Detection of a Two-Planet System in a Low Magnification Microlensing Event
• Spectroscopic Mass and Host-star Metallicity Measurements for Newly Discovered Microlensing Planet OGLE-2018-BLG-0740Lb
• Extending the Planetary Mass Function to Earth Mass by Microlensing at Moderately High Magnification
• OGLE-2018-BLG-0532Lb: Cold Neptune With Possible Jovian Sibling
• One Planet or Two Planets? The Ultra-sensitive Extreme-magnification Microlensing Event KMT-2019-BLG-1953
• KMT-2019-BLG-0842Lb: A Cold Planet Below the Uranus/Sun Mass Ratio
• KMT-2019-BLG-0797: binary-lensing event occurring on a binary stellar system
• KMT-2018-BLG-1292: A Super-Jovian Microlens Planet in the Galactic Plane
• OGLE-2017-BLG-1130: The First Binary Gravitational Microlens Detected From Spitzer Only
• A Pair of Planets Likely in Mean-motion Resonance From Gravitational Microlensing
• OGLE-2019-BLG-0960Lb: The Smallest Microlensing Planet

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• TOI-530b: A giant planet transiting an M dwarf detected by TESS
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