A predicted astrometric microlensing event by a nearby white dwarf

McGill, Peter; Smith, Leigh C.; Evans, N. W.; Belokurov, Vasily; Smart, R. L.

doi:10.1093/mnrasl/sly066

Cited by 31 publications

(27 citation statements)

References 27 publications

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“…A further source that passes multiple background sources is the white dwarf LAWD 37, for which we assume a mass of 0.65 M . Its most promising event, which was first predicted by McGill et al (2018), is in November 2019. McGill et al (2018) also mention that Gaia might be able to determine the mass with an accuracy of 3%, however this was done without knowing the scanning law for the extended mission.…”

Section: Multiple Background Sourcesmentioning

confidence: 99%

“…Its most promising event, which was first predicted by McGill et al (2018), is in November 2019. McGill et al (2018) also mention that Gaia might be able to determine the mass with an accuracy of 3%, however this was done without knowing the scanning law for the extended mission. We expect an uncertainty for the mass determination by Gaia of 0.12 M , which corresponds to 19%.…”

Section: Multiple Background Sourcesmentioning

confidence: 99%

“…The first systematic search for astrometric microlensing events was done by Salim & Gould (2000). Using the first data release of the Gaia mission (Gaia Collaboration 2016), McGill et al (2018) predicted one event caused by a nearby white dwarf. Currently, precise predictions (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Expectations on mass determination using astrometric microlensing by Gaia

Klüter

Bastian

Wambsganß

2020

A&A

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Context. Astrometric gravitational microlensing can be used to determine the mass of a single star (the lens) with an accuracy of a few percent. To do so, precise measurements of the angular separations between lens and background star with an accuracy below 1 milli − arcsec at different epochs are needed. Therefore only the most accurate instruments can be used. However, since the timescale is on the order of months to years, the astrometric deflection might be detected by Gaia, even though each star is only observed on a low cadence. Aims. We want to show how accurately Gaia can determine the mass of the lensing star. Methods. Using conservative assumptions based on the results of the second Gaia data release (Gaia DR2), we simulated the individual Gaia measurements for 501 predicted astrometric microlensing events during the Gaia era (2014.5–2026.5). For this purpose we used the astrometric parameters of Gaia DR2, as well as an approximative mass based on the absolute G magnitude. By fitting the motion of the lens and source simultaneously, we then reconstructed the 11 parameters of the lensing event. For lenses passing by multiple background sources, we also fitted the motion of all background sources and the lens simultaneously. Using a Monte-Carlo simulation we determined the achievable precision of the mass determination. Results. We find that Gaia can detect the astrometric deflection for 114 events. Furthermore, for 13 events Gaia can determine the mass of the lens with a precision better than 15% and for 13 + 21 = 34 events with a precision of 30% or better.

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Section: Multiple Background Sourcesmentioning

confidence: 99%

Section: Multiple Background Sourcesmentioning

confidence: 99%

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Expectations on mass determination using astrometric microlensing by Gaia

Klüter

Bastian

Wambsganß

2020

A&A

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“…That is, we must determine when a foreground lens will align closely enough with a background source to produce a detectable microlensing effect. Gaia data has proven ideal for predicting astrometric microlensing events (McGill et al 2018;Bramich 2018, hereafter B18). In particular, data release 2, which provides excellent astrometric solutions for ∼ 1.7 billion objects (Gaia Collaboration et al 2018, hereafter GDR2), has opened up the flood gates.…”

Section: Introductionmentioning

confidence: 99%

Ongoing astrometric microlensing events from VVV and Gaia

McGill

Smith

Evans

et al. 2019

Monthly Notices of the Royal Astronomical Society: Letters

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We extend predictive microlensing event searches using the Vista Variables in the Via Lactea survey and the second Gaia data release. We identify two events with maxima in 2019 that require urgent follow-up. First, we predict that the nearby M2 dwarf L 338-152 will align with a background source with a closest approach of 35 +35 −23 mas on 2019 November 16 +28 −27 d. This will cause a peak astrometric shift and photometric amplification of the background source of 2.7 +3.5 −1.5 mas and 5.6 +143.2 −5.2 mmag respectively. This event should be astrometrically detectable by both the Hubble Space Telescope (HST) and the Spectro-Polarimetric High-contrast Exoplanet Research instrument on the Very Large Telescope. Secondly, we predict the likely K dwarf NLTT 45128 will lens a background source with a closest approach of 105.3 +12.2 −11.7 mas on 2019 September 26 +15 −15 d. This will produce a peak astrometric shift of 0.329 +0.065 −0.059 mas. NLTT 45128 is only 3.6 magnitudes brighter than the background source which makes it an excellent candidate for follow-up with HST. Characterisation of these signals will allow direct gravitational masses to be inferred for both L 338-152 and NLTT 45128 with an estimated precision of ∼ 9 and ∼ 13 per cent respectively.

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“…Nowadays the most precise predictions make use of astrometric data from the Gaia satellite (Gaia Collaboration et al 2016). Using Gaia DR1, the first data release, McGill et al (2018) predicted one event caused by a white dwarf in 2019. With the second Gaia data release (Gaia DR2, Gaia Collaboration et al 2018) about 5700 events were predicted, either by using solely Gaia DR2 (Klüter et al 2018a;Bramich 2018;Klüter et al 2018b;McGill et al 2019b) or by combining it with additional catalogues McGill et al 2019a), such as Pan-STARRS (Chambers et al 2016) 1 , or VVV, (Minniti et al 2010) 2 , respectively.…”

Section: Introductionmentioning

confidence: 99%

Prediction of astrometric microlensing events from Gaia DR2 proper motions

Klüter

Bastian

Demleitner

et al. 2018

A&A

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Context. Astrometric gravitational microlensing is an excellent tool to determine the mass of stellar objects. Using precise astrometric measurements of the lensed position of a background source in combination with accurate predictions of the positions of the lens and the unlensed source it is possible to determine the mass of the lens with an accuracy of a few percent. Aims. Making use of the recently published Gaia Data Release 2 (DR2) catalogue, we want to predict astrometric microlensing events caused by foreground stars with high proper motion passing a background source in the coming decades. Methods. We selected roughly 148 000 high-proper-motion stars from Gaia DR2 with µ tot > 150 mas/yr as potential lenses. We then searched for background sources close to their paths. Using the astrometric parameters of Gaia DR2, we calculated the future positions of source and lens. With a nested-intervals algorithm we determined the date and separation of the closest approach. Using Gaia DR2 photometry we determined an approximate mass of the lens, which we used to calculate the expected microlensing effects. Results. We predict 3914 microlensing events caused by 2875 different lenses between 2010 and 2065, with expected shifts larger than 0.1 mas between the lensed and unlensed positions of the source. Of those, 513 events are expected to happen between 2014.5 -2026.5 and might be measured by Gaia. For 127 events we also expect a magnification between 1 mmag and 3 mag.Conclusions.

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A predicted astrometric microlensing event by a nearby white dwarf

Cited by 31 publications

References 27 publications

Expectations on mass determination using astrometric microlensing by Gaia

Expectations on mass determination using astrometric microlensing by Gaia

Ongoing astrometric microlensing events from VVV and Gaia

Prediction of astrometric microlensing events from Gaia DR2 proper motions

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