MaBμlS-2: high-precision microlensing modelling for the large-scale survey era

Specht, D.; Kerins, E.; Awiphan, S.; Robin, A. C.

doi:10.1093/mnras/staa2375

Cited by 10 publications

(16 citation statements)

References 33 publications

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“…Although Mróz et al (2017) shows the likelihood peak at α bd ∼ 0.8 using the Galactic model based on Han & Gould (1995 with simplified disk kinematics, Specht et al (2020) shows the likelihood peak at α bd = −0.1, and 0.8 (-0.8 in their definition) is significantly disfavored according to their Figure 4. Specht et al (2020) used the Besançon model (Robin et al 2003(Robin et al , 2012(Robin et al , 2017 for their analysis using a more realistic model for disk kinematics. However, the Besançon model also has some unrealistic features, as discussed by Penny et al (2019), such as the small Galactic bar angle of 13 • compared to 25 • -30 • implied by other observations (see a review by Bland-Hawthorn & Gerhard 2016).…”

Section: Introductionmentioning

confidence: 93%

“…Another case motivating this concern is the IMF in brown dwarf mass range of M < 0.08 M , parameterized by a slope, α bd , with dN/dM ∝ M −α bd , and inferred by the t E distribution from the OGLE-IV survey (Mróz et al 2017). Although Mróz et al (2017) shows the likelihood peak at α bd ∼ 0.8 using the Galactic model based on Han & Gould (1995 with simplified disk kinematics, Specht et al (2020) shows the likelihood peak at α bd = −0.1, and 0.8 (-0.8 in their definition) is significantly disfavored according to their Figure 4. Specht et al (2020) used the Besançon model (Robin et al 2003(Robin et al , 2012(Robin et al , 2017 for their analysis using a more realistic model for disk kinematics.…”

Section: Introductionmentioning

confidence: 99%

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A Parametric Galactic Model toward the Galactic Bulge Based on Gaia and Microlensing Data

Koshimoto,

Baba,

Bennett

2021

Preprint

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We developed a parametric Galactic model toward the Galactic bulge by fitting to spatial distributions of the Gaia DR2 disk velocity, VVV proper motion, BRAVA radial velocity, OGLE-III red clump star count, and OGLE-IV star count and microlens rate, optimized for use in microlensing studies. We include the asymmetric drift of Galactic disk stars and the dependence of velocity dispersion on Galactic location in kinematic model, which has been ignored in most previous models used for microlensing studies. We show that our model predicts a microlensing parameter distribution that is significantly different from the one with a typically used model in the previous studies. Through our modeling, we estimate various fundamental model parameters for our Galaxy, including the initial mass function (IMF) in the inner Galaxy. Combined constraints from star counts and the microlensing event timescale distribution from the OGLE-IV survey, in addition to a prior on the bulge stellar mass, enable us to successfully measure IMF slopes using a broken power law form over a broad mass range, α bd = 0.22 +0.20 −0.55 for M < 0.08 M , α ms = 1.16 +0.08 −0.15 for 0.08 M ≤ M < M br , and α hm = 2.32 +0.14 −0.10 for M ≥ M br , as well as a break mass at M br = 0.90 +0.05 −0.14 M . This is significantly different from the Kroupa IMF for local stars, but similar to the Zoccali IMF measured from a bulge luminosity function. We also estimate the dark matter mass fraction in the bulge region of 28 ± 7% which could be larger than a previous estimate. Because our model is purely parametric, it can be universally applied using the parameters provided in this paper.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

A Parametric Galactic Model toward the Galactic Bulge Based on Gaia and Microlensing Data

Koshimoto,

Baba,

Bennett

2021

Preprint

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“…the mass measurement) of events. To list a few, this includes the consideration of limb-darkening for a more accurate To assess the number of FFPs where such mass constraints could be obtained, we used a specially modified version of the MaBµlS-2 simulator 3 (Specht et al 2020) to allow for FFPs and to consider simultaneous parallax by separated observatories. MaBµlS-2 employs a synthetic population of microlensing lenses and source stars seeded from version 1307 of the Besançon Galactic model (BGM) (Robin et al 2012(Robin et al , 2014.…”

Section: Simulation Of Joint Observationsmentioning

confidence: 99%

“…MaBµlS-2 employs a synthetic population of microlensing lenses and source stars seeded from version 1307 of the Besançon Galactic model (BGM) (Robin et al 2012(Robin et al , 2014. MaBµlS-2 has been demonstrated by Specht et al (2020) to provide an accurate match to the 8,000-event sample from the OGLE-IV survey (Mróz et al 2019c). Using the BGM, MaBµlS-2 simulates the microlensing event rate from the synthetic stellar catalogues produced.…”

Section: Simulation Of Joint Observationsmentioning

confidence: 99%

“…The overall procedure for comput-ing the microlensing rate, optical depth and average timescale follows the formalism detailed in Specht et al ( 2020) with a few differences. Firstly, our signal-to-noise (S/N) selection involves a time-averaged statistic rather than the S/N at peak used in Specht et al (2020). Specifically, we demand a ∆χ 2 between the synthetically-generated microlens lightcurve and a best fit constant flux model of at least 125, with at least 6 points reaching 3σ above the baseline.…”

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.

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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.

show abstract

MaBμlS-2: high-precision microlensing modelling for the large-scale survey era

Cited by 10 publications

References 33 publications

A Parametric Galactic Model toward the Galactic Bulge Based on Gaia and Microlensing Data

A Parametric Galactic Model toward the Galactic Bulge Based on Gaia and Microlensing Data

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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