A Search for Predicted Astrometric Microlensing Events by Nearby Brown Dwarfs*

Luberto, Judah; Martin, Emily C.; McGill, Peter; Leauthaud, Alexie; Skemer, Andrew J.; Lu, Jessica R.

doi:10.3847/1538-3881/ac9a41

Cited by 8 publications

(2 citation statements)

References 65 publications

(105 reference statements)

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“…The GBTDS will survey ≈2 deg 2 over 5 yr in the infrared wavelengths. In addition to benefiting from increased microlensing event rates in the infrared (e.g., Gould 1994;McGill et al 2019;Husseiniova et al 2021;Kaczmarek et al 2022;Luberto et al 2022;Kaczmarek et al 2024;Kondo et al 2023;Wen et al 2023), the GBTDS will take simultaneous photometry and astrometry at a 15 minute cadence during an observing season.…”

Section: Introductionmentioning

confidence: 99%

Astrometric Microlensing by Primordial Black Holes with the Roman Space Telescope

Fardeen,

McGill,

Perkins

et al. 2024

ApJ

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Primordial black holes (PBHs) could explain some fraction of dark matter and shed light on many areas of early-Universe physics. Despite over half a century of research interest, a PBH population has so far eluded detection. The most competitive constraints on the fraction of dark matter comprised of PBHs (f DM) in the (10−9–10)M ⊙ mass ranges come from photometric microlensing and bound f DM ≲ 10−2–10−1. With the advent of the Roman Space Telescope with its submilliarcsecond astrometric capabilities and its planned Galactic Bulge Time Domain Survey (GBTDS), detecting astrometric microlensing signatures will become routine. Compared with photometric microlensing, astrometric microlensing signals are sensitive to different lens masses–distance configurations and contain different information, making it a complimentary lensing probe. At submilliarcsecond astrometric precision, astrometric microlensing signals are typically detectable at larger lens–source separations than photometric signals, suggesting a microlensing detection channel of pure astrometric events. We use a Galactic simulation to predict the number of detectable microlensing events during the GBTDS via this pure astrometric microlensing channel. Assuming an absolute astrometric precision floor for bright stars of 0.1 mas for the GBTDS, we find that the number of detectable events peaks at ≈103 f DM for a population of 1M ⊙ PBHs and tapers to ≈10f DM and ≈100f DM at 10−4 M ⊙ and 103 M ⊙, respectively. Accounting for the distinguishability of PBHs from stellar lenses, we conclude the GBTDS will be sensitive to a PBH population at f DM down to ≈10−1–10−3 for (10−1–102)M ⊙ likely yielding novel PBH constraints.

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Section: Introductionmentioning

confidence: 99%

Astrometric Microlensing by Primordial Black Holes with the Roman Space Telescope

Fardeen,

McGill,

Perkins

et al. 2024

ApJ

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“…Then, following Gaia Data Release 2 (Gaia Collaboration et al 2018) many independent studies searched for both astrometric and photometric events resulting in ∼ 5000 predictions (Klüter et al 2018a,b;Bramich 2018;Bramich & Nielsen 2018;Mustill et al 2018;Nielsen & Bramich 2018a;Ofek 2018;McGill et al 2019aMcGill et al ,b, 2020. Most recently Klüter et al (2021) searched for predicted microlensing events using Gaia Early Data Release 3 (GEDR3; Gaia Collaboration et al 2021) finding 1758 new events, and Luberto et al (2022) searched for events with brown dwarf lenses.…”

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confidence: 99%

First semi-empirical test of the white dwarf mass–radius relationship using a single white dwarf via astrometric microlensing

McGill

Anderson

Casertano

et al. 2022

Monthly Notices of the Royal Astronomical Society

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In November 2019 the nearby single, isolated DQ-type white dwarf LAWD 37 (WD 1142-645) aligned closely with a distant background source and caused an astrometric microlensing event. Leveraging astrometry from Gaia and followup data from the Hubble Space Telescope we measure the astrometric deflection of the background source and obtain a gravitational mass for LAWD 37. The main challenge of this analysis is in extracting the lensing signal of the faint background source whilst it is buried in the wings of LAWD 37’s point spread function. Removal of LAWD 37’s point spread function induces a significant amount of correlated noise which we find can mimic the astrometric lensing signal. We find a deflection model including correlated noise caused by the removal of LAWD 37’s point spread function best explains the data and yields a mass for LAWD 37 of 0.56 ± 0.08 M⊙. This mass is in agreement with the theoretical mass-radius relationship and cooling tracks expected for CO core white dwarfs. Furthermore, the mass is consistent with no or trace amounts of hydrogen that is expected for objects with helium-rich atmospheres like LAWD 37. We conclude that further astrometric followup data on the source is likely to improve the inference on LAWD 37’s mass at the ≈3 percent level and definitively rule out purely correlated noise explanations of the data. This work provides the first semi-empirical test of the white dwarf mass-radius relationship using a single, isolated white dwarf and supports current model atmospheres of DQ white dwarfs and white dwarf evolutionary theory.

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KMT-2022-BLG-0475Lb and KMT-2022-BLG-1480Lb: Microlensing ice giants detected via the non-caustic-crossing channel

Han¹,

Lee²,

Bond³

et al. 2023

A&A

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Aims. We investigate the microlensing data collected in the 2022 season from high-cadence microlensing surveys in order to find weak signals produced by planetary companions to lenses. Methods. From these searches, we find that two lensing events, KMT-2022-BLG-0475 and KMT-2022-BLG-1480, exhibit weak short-term anomalies. From a detailed modeling of the lensing light curves, we determine that the anomalies are produced by planetary companions with a mass ratio to the primary of q ~ 1.8 × 10−4 for KMT-2022-BLG-0475L and q ~ 4.3 × 10−4 for KMT-2022-BLG-1480L. Results. We estimate that the host and planet masses and the projected planet-host separation are (Mh/M⊙, Mp/MU, a⊥/au) = (0.43−0.23+0.35, 1.73−0.92+1.42, 2.03−0.38+0.25) for KMT-2022-BLG-0475L and (0.18−0.09+0.16, 1.82−0.92+1.60, 1.22−0.14+0.15) for KMT-2022-BLG-1480L, where MU denotes the mass of Uranus. The two planetary systems have some characteristics in common: the primaries of the lenses are early-mid M dwarfs that lie in the Galactic bulge, and the companions are ice giants that lie beyond the snow lines of the planetary systems.

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A Search for Predicted Astrometric Microlensing Events by Nearby Brown Dwarfs*

Cited by 8 publications

References 65 publications

Astrometric Microlensing by Primordial Black Holes with the Roman Space Telescope

Astrometric Microlensing by Primordial Black Holes with the Roman Space Telescope

First semi-empirical test of the white dwarf mass–radius relationship using a single white dwarf via astrometric microlensing

KMT-2022-BLG-0475Lb and KMT-2022-BLG-1480Lb: Microlensing ice giants detected via the non-caustic-crossing channel

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