Microlens mass determination for<i>Gaia</i>’s predicted photometric events

McGill, Peter; Smith, Leigh C.; Evans, N. W.; Belokurov, Vasily; Zhang, ZH

doi:10.1093/mnras/sty3344

Cited by 16 publications

(14 citation statements)

References 44 publications

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“…The Einstein radius can also be obtained from the event timescale t E if the relative proper motion µ rel of the lens and the source are known, since θ E = µ rel t E (µ rel is the length of the µ rel vector). To date, however, there have only been a limited number of measurements of µ rel based on a detection of the luminous lens a decade or so after the event (e.g., Kozłowski et al 2007;Batista et al 2015;Beaulieu et al 2018;Bramich 2018;McGill et al 2018McGill et al , 2019. Moreover, this method would not work for dark lenses, except for known pulsars, as shown by, Dai et al (2010), Dai et al (2015) and Ofek (2018), among others.…”

Section: Introductionmentioning

confidence: 99%

Constraining the masses of microlensing black holes and the mass gap with Gaia DR2

Wyrzykowski

Mandel

2020

A&A

134

114

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Context. Gravitational microlensing is sensitive to compact-object lenses in the Milky Way, including white dwarfs, neutron stars, or black holes, and could potentially probe a wide range of stellar-remnant masses. However, the mass of the lens can be determined only in very limited cases, due to missing information on both source and lens distances and their proper motions. Aims. Our aim is to improve the mass estimates in the annual parallax microlensing events found in the eight years of OGLE-III observations towards the Galactic Bulge with the use of Gaia Data Release 2 (DR2). Methods. We use Gaia DR2 data on distances and proper motions of non-blended sources and recompute the masses of lenses in parallax events. We also identify new events in that sample which are likely to have dark lenses; the total number of such events is now 18. Results. The derived distribution of masses of dark lenses is consistent with a continuous distribution of stellar-remnant masses. A mass gap between neutron star and black hole masses in the range between 2 and 5 solar masses is not favoured by our data, unless black holes receive natal kicks above 20-80 km/s. We present eight candidates for objects with masses within the putative mass gap, including a spectacular multi-peak parallax event with mass of 2.4 +1.9 −1.3 M located just at 600 pc. The absence of an observational mass gap between neutron stars and black holes, or conversely the evidence of black hole natal kicks if a mass gap is assumed, can inform future supernova modelling efforts.

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Section: Introductionmentioning

confidence: 99%

Constraining the masses of microlensing black holes and the mass gap with Gaia DR2

Wyrzykowski

Mandel

2020

A&A

134

114

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“…In summary, microlensing searches can help address limitations of more common observational methods and extend compact object observations to isolated objects without a binary companion. In the context of these searches, many studies have been performed to constrain the mass function of compact objects using observed photometric and astrometric microlensing events (Gould 2000;Wyrzykowski et al 2016;Sahu et al 2017;Ofek 2018;McGill et al 2019;Wyrzykowski & Mandel 2020;Mroz et al 2021). With the increasing number of microlensing surveys and improved monitoring of high stellar density regions like GCs, it should also be possible to obtain detailed information on the masses and kinematics of compact object populations in GCs.…”

Section: Discussionmentioning

confidence: 99%

Gravitational Microlensing Rates in Milky Way Globular Clusters

Kıroğlu,

Weatherford,

Kremer

et al. 2021

Preprint

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Many recent observational and theoretical studies suggest globular clusters (GCs) host compact object populations large enough to play dominant roles governing their overall dynamical evolution. Yet direct detection, particularly of black holes and neutron stars, remains rare and limited to special cases, such as when these objects reside in close binaries with bright companions. Here we examine the potential of microlensing detections to further constrain these dark populations. Based on stateof-the-art GC models from the CMC Cluster Catalog, we estimate the microlensing event rates for black holes, neutron stars, white dwarfs, and, for comparison, also for M dwarfs in Milky Way GCs, as well as the effects of different initial conditions on these rates. Among compact objects, we find that white dwarfs dominate the microlensing rates, simply because they dominate by numbers. We show that microlensing detections are in general more likely in GCs with higher initial densities, especially in clusters that undergo core-collapse where the lenses are white dwarfs. We also estimate microlensing rates in the specific cases of M22 and 47 Tuc using our best-fitting models for these GCs. Because their positions on the sky lie near the rich stellar backgrounds of the Galactic bulge and the Small Magellanic Cloud, respectively, these clusters are among the Galactic GCs best-suited for dedicated microlensing surveys.

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“…This degeneracy means that physical interpretation of the event is ambiguous in the absence of further data. Some microlensing events deviate from the standard form, or can be predicted ahead of time, enabling the degeneracies to be wholly or partially lifted (e.g., Gould 1992Gould , 1994Bennett 1998;Evans 2003;McGill et al 2019a), though these exotica can be hard to pick out. In this paper, we direct our attention exclusively to standard PSPL events.…”

Section: Introductionmentioning

confidence: 99%

A microlensing search of 700 million VVV light curves

Husseiniova,

McGill,

Smith

et al. 2021

Preprint

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The VISTA Variables in the Vıa Lactea (VVV) survey and its extension, have been monitoring about 560 square degrees of sky centred on the Galactic bulge and inner disc for nearly a decade. The photometric catalogue contains of order 10 9 sources monitored in the 𝐾 𝑠 band down to 18 mag over hundreds of epochs from 2010-2019. Using these data we develop a decision tree classifier to identify microlensing events. As inputs to the tree, we extract a few physically motivated features as well as simple statistics ensuring a good fit to a microlensing model both on and off the event amplification. This produces a fast and efficient classifier trained on a set of simulated microlensing events and catacylsmic variables, together with flat baseline light curves randomly chosen from the VVV data. The classifier achieves 97 per cent accuracy in identifying simulated microlensing events in a validation set. We run the classifier over the VVV data set and then visually inspect the results, which produces a catalogue of 1 959 microlensing events. For these events, we provide the Einstein radius crossing time via a Bayesian analysis. The spatial dependence on recovery efficiency of our classifier is well characterised, and this allows us to compute spatially resolved completeness maps as a function of Einstein crossing time over the VVV footprint. We compare our approach to previous microlensing searches of the VVV. We highlight the importance of Bayesian fitting to determine the microlensing parameters for events with surveys like VVV with sparse data.

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Microlens mass determination forGaia’s predicted photometric events

Cited by 16 publications

References 44 publications

Constraining the masses of microlensing black holes and the mass gap with Gaia DR2

Constraining the masses of microlensing black holes and the mass gap with Gaia DR2

Gravitational Microlensing Rates in Milky Way Globular Clusters

A microlensing search of 700 million VVV light curves

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