Probability of simultaneous parallax detection for free-floating planet microlensing events near Galactic Centre

Ban, Makiko

doi:10.1093/mnras/staa786

Cited by 10 publications

(16 citation statements)

References 40 publications

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“…Initially called the Wide Field Infrared Survey Telescope (WFIRST; Spergel et al 2015), Roman is currently planned to conduct three Core Community Surveys: the High Latitude Survey (Troxel et al 2019), the Type Ia Supernova Survey (photometric, Hounsell et al 2018;and spectroscopic), and the Galactic Exoplanet Survey . These surveys will be accompanied by a Guest Observer program (including notionally 25% of observing time) and a demonstration of numerous new-to-space technologies with the Coronagraph Instrument (CGI; Debes et al 2016;Bailey et al 2019).…”

Section: The Nancy Grace Roman Space Telescope and Its Galactic Exoplmentioning

confidence: 99%

Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. II. Free-floating Planet Detection Rates*

et al. 2020

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The Nancy Grace Roman Space Telescope (Roman) will perform a Galactic Exoplanet Survey (RGES) to discover bound exoplanets with semimajor axes greater than 1 au using gravitational microlensing. Roman will even be sensitive to planetary-mass objects that are not gravitationally bound to any host star. Such free-floating planetarymass objects (FFPs) will be detected as isolated microlensing events with timescales shorter than a few days. A measurement of the abundance and mass function of FFPs is a powerful diagnostic of the formation and evolution of planetary systems, as well as the physics of the formation of isolated objects via direct collapse. We show that Roman will be sensitive to FFP lenses that have masses from that of Mars (0.1 M ⊕) to gas giants (M100 M ⊕) as isolated lensing events with timescales from a few hours to several tens of days, respectively. We investigate the impact of the detection criteria on the survey, especially in the presence of finite-source effects for low-mass lenses. The number of detections will depend on the abundance of such FFPs as a function of mass, which is at present poorly constrained. Assuming that FFPs follow the fiducial mass function of cold, bound planets adapted from Cassan et al., we estimate that Roman will detect ∼250 FFPs with masses down to that of Mars (including ∼60 with masses M ⊕). We also predict that Roman will improve the upper limits on FFP populations by at least an order of magnitude compared to currently existing constraints. Unified Astronomy Thesaurus concepts: Gravitational microlensing (672); Free floating planets (549); Space telescopes (1547); Exoplanet detection methods (489)

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Section: The Nancy Grace Roman Space Telescope and Its Galactic Exoplmentioning

confidence: 99%

Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. II. Free-floating Planet Detection Rates*

et al. 2020

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“…However, the authors show that simultaneous observation from the Euclid mission would constrain the microlensing parallax down to the FFP regime if the separation between the two mission is sufficiently large. This was confirmed by the independent analysis of Ban (2020), that demonstrates that the parallax will be measurable for a large fraction of events due to FFP.…”

Section: Introductionmentioning

confidence: 57%

Euclid-Roman joint microlensing survey: Early mass measurement, free floating planets, and exomoons

Bachelet

Specht

Penny

et al. 2022

A&A

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As the Kepler mission has done for hot exoplanets, the ESA Euclid and NASA Roman missions have the potential to create a breakthrough in our understanding of the demographics of cool exoplanets, including unbound, or free-floating, planets (FFPs). Roman will dedicate part of its core survey program to the detection of cool exoplanets via microlensing, while Euclid may undertake a microlensing program as an ancillary science goal. In this study, we demonstrate the complementarity of the two missions and propose two joint surveys to better constrain the mass and distance of microlensing events. We first demonstrate that an early brief Euclid survey (~7 h) of the Roman microlensing fields will allow the measurement of at least 30% of the events’ relative proper motions µrel and 42% of the lens magnitudes. This survey would place strong constraints on the mass and distance on thousands of microlensing events observed by Roman just after the first year of observation. Then, we study the potential of simultaneous observations by Roman and Euclid to enable the measurement of the microlensing parallax for the shortest microlensing events and, ultimately, obtain a direct measurement of the masses, distances, and transverse motions of FFPs. Using detailed simulations of the joint detection yield we show that within one year Roman-Euclid observations will be at least an order of magnitude more sensitive than current ground-based measurements. The recent tentative detection of an excess of short-duration events by the OGLE survey is consistent with a scenario of up to ten Earth-mass FFPs per Galactic star. For such a scenario a joint Roman-Euclid campaign should detect around 130 FFP events within a year, including 110 with measured parallax that strongly constrain the FFP mass, and around 30 FFP events with direct mass and distance measurements. The ability of the joint survey to completely break the microlens mass-distance-velocity degeneracy for a significant subset of events provides a unique opportunity to verify unambiguously the FFP hypothesis or else place abundance limits for FFPs between Earth and Jupiter masses that are up to two orders of magnitude stronger than provided by ground-based surveys. Finally, we study the capabilities of the joint survey to enhance the detection and characterization of exomoons, and find that it could lead to the detection of the first exomoon.

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“…In this section, we explore, in a statistical sense, the capabilities that offer a Roman and Euclid joint-survey to detect and characterize microlensing events due to FFPs. Therefore, this work is in the lineage of the previous work from Johnson et al (2020) and Ban (2020), but, as detailed below, implements several refinements that can play a significant role on the characterization (i.e. the mass measurement) of events.…”

Section: Simulation Of Joint Observationsmentioning

confidence: 99%

“…A comparison can be made to the parallax detection rates from Ban (2020), who used different methods for determining the event selection criteria along with microlensing calculations based on an earlier version of MaBµlS. Ban (2020) considers a single line of sight at (l, b) = (1.0 • , −1.75 • ) for various telescope combinations (including the Vera Rubin Observatory, formerly LSST).…”

Section: Simulation Of Joint Observationsmentioning

confidence: 99%

“…Differences in calculation methodology make direct comparison difficult. Ban (2020) does not require a detection of finite source effects (although finite source effects without limb-darkening are taken into consideration when calculating simulated lightcurve photometry) and uses a signalto-noise at peak selection (with S/N ≥ 50), as opposed to the time-integrated signal to noise used in the present study. This difference in signal-to-noise selection drives the main difference between results, with a rate per square degree per 60 days of observation of Γ Earth = 5.2 for this work and Γ Earth = 4.9 for Ban (2020), with a larger discrepancy for the rates of Jupiter mass FFPs of Γ Jupiter = 104 for this work and Γ Jupiter = 31 for Ban (2020), attributable to the effect of using a time integrated signalto-noise selection on events of longer timescales.…”

Section: Simulation Of Joint Observationsmentioning

confidence: 99%

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Euclid-Roman joint microlensing survey: early mass measurement, free floating planets and exomoons

Bachelet¹,

Specht²,

Penny³

et al. 2022

Preprint

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As the Kepler mission has done for hot exoplanets, the ESA Euclid and NASA Roman missions have the potential to create a breakthrough in our understanding of the demographics of cool exoplanets, including unbound, or "free-floating", planets (FFPs). Roman will dedicate part of its core survey program to the detection of cool exoplanets via microlensing, while Euclid may undertake a microlensing program as an ancillary science goal. In this study, we demonstrate the complementarity of the two missions and propose two joint-surveys to better constrain the mass and distance of microlensing events. We first demonstrate that an early brief Euclid survey (∼ 7 h) of the Roman microlensing fields will allow the measurement of at least 30% of the events' relative proper motions µ rel and 42% of the lens magnitudes. This survey would place strong constraints on the mass and distance on thousands of microlensing events observed by Roman just after the first year of observation. Then, we study the potential that simultaneous observations by Roman and Euclid to enable the measurement of the microlensing parallax for the shortest microlensing events and, ultimately, obtain a direct measurement of the masses, distances and transverse motions of FFPs. Using detailed simulations of the joint detection yield we show that within one year Roman-Euclid observations will be at least an order of magnitude more sensitive than current groundbased measurements. The recent tentative detection of an excess of short-duration events by the OGLE survey is consistent with a scenario of up to 10 Earth-mass FFPs per Galactic star. For such a scenario a joint Roman-Euclid campaign should detect around 130 FFP events within a year, including 110 with measured parallax that strongly constrain the FFP mass, and around 30 FFP events with direct mass and distance measurements. The ability of the joint survey to completely break the microlens mass-distance-velocity degeneracy for a significant subset of events provides a unique opportunity to verify unambiguously the FFP hypothesis or else place abundance limits for FFPs between Earth and Jupiter masses that are up to two orders of magnitude stronger than provided by groundbased surveys. Finally, we study the capabilities of the joint survey to enhance the detection and charcterization of exomoons, and found that it could lead to the detection of the first exomoon.

show abstract

Probability of simultaneous parallax detection for free-floating planet microlensing events near Galactic Centre

Cited by 10 publications

References 40 publications

Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. II. Free-floating Planet Detection Rates*

Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. II. Free-floating Planet Detection Rates*

Euclid-Roman joint microlensing survey: Early mass measurement, free floating planets, and exomoons

Euclid-Roman joint microlensing survey: early mass measurement, free floating planets and exomoons

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