Martin Dominik
University of St Andrews, Physics and Astronomy, Faculty Member
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Context. The timescale of a microlensing event scales as a square root of a lens mass. Therefore, long-lasting events are important candidates for massive lenses, including black holes. Aims. Here, we present the analysis of the Gaia18cbf... more
Context. The timescale of a microlensing event scales as a square root of a lens mass. Therefore, long-lasting events are important candidates for massive lenses, including black holes. Aims. Here, we present the analysis of the Gaia18cbf microlensing event reported by the Gaia Science Alerts system. It exhibited a long timescale and features that are common for the annual microlensing parallax effect. We deduce the parameters of the lens based on the derived best fitting model. Methods. We used photometric data collected by the Gaia satellite as well as the follow-up data gathered by the ground-based observatories. We investigated the range of microlensing models and used them to derive the most probable mass and distance to the lens using a Galactic model as a prior. Using a known mass-brightness relation, we determined how likely it is that the lens is a main-sequence (MS) star. Results. This event is one of the longest ever detected, with the Einstein timescale of tE = 491.41−84...
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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,... more
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 ...
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Microlensing searches for planets are sensitive to small, cold exoplanets from 1–6 AU from their host stars and therefore probe an important part of parameter space. Other techniques would require many years of observations, often from... more
Microlensing searches for planets are sensitive to small, cold exoplanets from 1–6 AU from their host stars and therefore probe an important part of parameter space. Other techniques would require many years of observations, often from space, to detect similar systems. Microlensing events can be characterised from only ground-based observations over a relatively short (≤100d) timescales. LCOGT and SUPA/St Andrews are building a robotic global network of telescopes that will be well suited to follow these events. Here we present preliminary results of the Galactic Bulge observing season 2010 March–October.
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33 Jean-Philippe Beaulieu1,3 Michael Albrow1,4 Dave Bennett1,5 Stéphane Brillant1,6 John A. R. Caldwell1,7 Johannes J. Calitz1,8 Arnaud Cassan1,9 Kem H. Cook1,10 Christian Coutures1,3 Stefan Dieters1,11 Martin Dominik1,2,12,13 Dijana... more
33 Jean-Philippe Beaulieu1,3 Michael Albrow1,4 Dave Bennett1,5 Stéphane Brillant1,6 John A. R. Caldwell1,7 Johannes J. Calitz1,8 Arnaud Cassan1,9 Kem H. Cook1,10 Christian Coutures1,3 Stefan Dieters1,11 Martin Dominik1,2,12,13 Dijana Dominis-Prester1,14 Jadzia Donatowicz1,15 Pascal Fouqué1,16 John Greenhill1,11 Kym Hill1,11 Matie Hoffman1,8 Uffe G. Jørgensen1,17 Stephen Kane1,18 Daniel Kubas1,6 Jean-Baptiste Marquette1,3 Ralph Martin1,19 Pieter Meintjes1,8 John Menzies1,20 Karen Pollard1,4 Kailash Sahu1,21 Christian Vinter1,17 Joachim Wambsganss1,9 Andrew Williams1,19 Kristian Woller1,17 Marta Zub1,9 Keith Horne1,2,12 Alasdair Allan2,22 Mike Bode2,23 Daniel M. Bramich1,2,24 Martin Burgdorf 2,23 Stephen Fraser2,23 Chris Mottram2,23 Nicholas Rattenbury2,25 Colin Snodgrass2,6 Iain Steele2,23 Yiannis Tsapras2,23
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The Probing Lensing Anomalies NETwork is an international collaboration that makes coordinated observations of on-going graviational microlensing events from four sites in the southern hemisphere. One of our primary goals is to detect... more
The Probing Lensing Anomalies NETwork is an international collaboration that makes coordinated observations of on-going graviational microlensing events from four sites in the southern hemisphere. One of our primary goals is to detect planets around other stars from their microlensing effect. During the 1998 bulge observing season we intensely monitored numerous microlensing events; one event was observed more than 500
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Gravitational deflection of starlight around the Sun during the 1919 total solar eclipse provided measurements that confirmed Einstein's general theory of relativity. We have used the Hubble Space Telescope to measure the analogous... more
Gravitational deflection of starlight around the Sun during the 1919 total solar eclipse provided measurements that confirmed Einstein's general theory of relativity. We have used the Hubble Space Telescope to measure the analogous process of astrometric microlensing caused by a nearby star, the white dwarf Stein 2051 B. As Stein 2051 B passed closely in front of a background star, the background star's position was deflected. Measurement of this deflection at multiple epochs allowed us to determine the mass of Stein 2051 B-the sixth-nearest white dwarf to the Sun-as 0.675 ± 0.051 solar masses. This mass determination provides confirmation of the physics of degenerate matter and lends support to white dwarf evolutionary theory.
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Research Interests: Physics, Organic Chemistry, Astrophysical Plasma, Gravitational Microlensing, Astrophysics, and 13 moreGravitational Lensing, Extrasolar planets, Search, Systems, Selection Criteria, Planetary Systems, Spatial Distribution, Light curves, Planet, Stars, Galactic bulge, Binary Lens, and parameter space
ABSTRACT. Amongst all techniques for detecting extra-solar planets, galactic microlensing is singled out by some unique characteristics, which allow to provide otherwise inaccessible information about their abundance and distribution of... more
ABSTRACT. Amongst all techniques for detecting extra-solar planets, galactic microlensing is singled out by some unique characteristics, which allow to provide otherwise inaccessible information about their abundance and distribution of properties. The detection efficiency reaches a maximum for orbital separations of 1–10 AU, giving preference to system like our own. Planets with large orbital periods can be detected since the planetary-signal duration is mass-dependent instead, ranging from hours (earths) to days (jupiters). Being limited by the size of the observed stars whose light is gravitationally bent by the parent stars of the planets, microlensing is the only technique able to pick up a signal from a second Earth at the time being, albeit with a small probability. The parent stars are located in the Galactic disk ( ∼ 1/3) or bulge ( ∼ 2/3) at several kpc distance. By monitoring M31 rather than the Galactic bulge, it is even possible to obtain upper abundance limits on giant...
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In order to obtain a census of planets with masses in the range of Earth to Jupiter, eight telescopes are being used by the combined microlensing campaign of the PLANET and RoboNet collaborations for high-cadence photometric... more
In order to obtain a census of planets with masses in the range of Earth to Jupiter, eight telescopes are being used by the combined microlensing campaign of the PLANET and RoboNet collaborations for high-cadence photometric round-the-clock follow-up of ongoing events, alerted by the OGLE and MOA surveys. In 2005 we detected a planet of 5.5 Earth masses at 2.6 AU from its parent 0.22 MA M star. This object is the first member of a new class of cold telluric planets. Its detection confirms the power of this method and, given our detection efficiency, suggests that these recently-detected planets may be quite common around M stars, as confirmed by subsequent detection of a ~ 13 Earth-mass planet. Using a network of dedicated 1 2-m-class telescopes, we have entered a new phase of planet discovery, and will be able to provide constraints on the abundance of frozen Super-Earths in the near future.
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We present a GPU-accelerated numerical approach for fast kernel and differential background solutions. The model image proposed in the Bramich Difference Image Analysis (DIA) algorithm is analogous to a very simple convolutional neural... more
We present a GPU-accelerated numerical approach for fast kernel and differential background solutions. The model image proposed in the Bramich Difference Image Analysis (DIA) algorithm is analogous to a very simple convolutional neural network (CNN), with a single convolutional filter (i.e. the kernel) and an added scalar bias (i.e. the differential background). Here, we do not solve for the discrete pixel array in the classical, analytical linear least-squares sense. Instead, by making use of PyTorch tensors (GPU compatible multidimensional matrices) and associated deep learning tools, we solve for the kernel via an inherently massively parallel optimization. By casting the DIA problem as a GPU-accelerated optimization that utilizes automatic differentiation tools, our algorithm is both flexible to the choice of scalar objective function, and can perform DIA on astronomical data sets at least an order of magnitude faster than its classical analogue. More generally, we demonstrate t...
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Most of the detected galactic microlensing events are commonly explained as due to microlensing of a pointlike source by a pointlike lens. We have found statistical methods to determine the goodness-of-fit for a specific model of source... more
Most of the detected galactic microlensing events are commonly explained as due to microlensing of a pointlike source by a pointlike lens. We have found statistical methods to determine the goodness-of-fit for a specific model of source and lens beyond the assumption that the errors are normal, which does not always hold. In particular, we argue that at least one weak binary lensing event has already been detected (MACHO LMC#1) and thereby confirm our former hypothesis (Dominik…
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The recent discovery of the first cool, rocky/icy exoplanet around a mainsequence star provides the first observational hint that planets like Earth are common in the universe. It was detected using gravitational microlensing from data of... more
The recent discovery of the first cool, rocky/icy exoplanet around a mainsequence star provides the first observational hint that planets like Earth are common in the universe. It was detected using gravitational microlensing from data of three independent observing teams under the lead of PLANET (Probing Lensing Anomalies NETwork), operating a common microlensing campaign with the UK-based RoboNet project. In the coming years intense microlensing observations will determine the abundance of cool rocky/icy planets around M-dwarfs and therefore provide the first observational test of models of planet formation and migration on objects that share their evolutionary history with Earth and other planets on which life had a chance to develop.
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Gravitational microlensing provides a unique technique to reveal information about extragalactic planets. A network of at least four 2m-class telescopes distributed around the northern hemisphere could probe 15-35 jupiters and 4-10... more
Gravitational microlensing provides a unique technique to reveal information about extragalactic planets. A network of at least four 2m-class telescopes distributed around the northern hemisphere could probe 15-35 jupiters and 4-10 saturns around M31 stars per year.
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For observed galactic microlensing events only one fit is usually presented, though, especially for a binary lens, several fits may be possible. This has been shown for the MACHO LMC#1 event (Dominik & Hirshfeld 1996). Here I discuss the... more
For observed galactic microlensing events only one fit is usually presented, though, especially for a binary lens, several fits may be possible. This has been shown for the MACHO LMC#1 event (Dominik & Hirshfeld 1996). Here I discuss the strong binary lens events OGLE#7 and DUO#2. It is shown that several models with a large variety of parameters are in accordance with the photometric data. For most of the fits, 1-sigma-bounds on the fit parameters are given. The variation of the parameters within the bounds is in some cases considerable. It is likely that other binary lens systems which will occur will have properties similar to the discussed events.
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During the last three years, several galactic microlensing events towards the Large Magellanic Cloud and the Galactic Bulge have been detected by four observing groups (MACHO, EROS, OGLE, DUO). Most of these are commonly explained as due... more
During the last three years, several galactic microlensing events towards the Large Magellanic Cloud and the Galactic Bulge have been detected by four observing groups (MACHO, EROS, OGLE, DUO). Most of these are commonly explained as due to microlensing of a point source by a point mass lens. In this paper, we discuss statistical methods to determine the goodness-of-fit for a specific model of source and lens beyond the assumption that the errors are normal. In particular, we argue that the MACHO LMC#1 event has been caused by a binary lens and thereby confirm our hypothesis (Dominik & Hirshfeld 1994). We also show that the binary lens fit is not unique by presenting alternative plausible binary lens fits. We emphasize that knowledge of the fraction of binaries among the observed microlensing events is crucial for estimating the mass distribution of the observed dark objects. We finally show that for each data set of parameters for a binary source, two physical configurations with different distances between the components exist which produce exactly the same light curve. (1 data file).
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Although point caustics harbour a larger potential for measuring the brightness profile of stars during the course of a microlensing event than (line-shaped) fold caustics, the effect of lens binarity significantly limits the achievable... more
Although point caustics harbour a larger potential for measuring the brightness profile of stars during the course of a microlensing event than (line-shaped) fold caustics, the effect of lens binarity significantly limits the achievable accuracy. Therefore, corresponding close-impact events make a less favourable case for limb-darkening measurements than those events that involve fold-caustic passages, from which precision measurements can easily and routinely be obtained. Examples involving later Bulge giants indicate that a ~ 10 % misestimate on the limb-darkening coefficient can result with the assumption of a single-lens model that looks acceptable, unless the precision of the photometric measurements is pushed below the 1 %-level even for these favourable targets. In contrast, measurement uncertainties on the proper motion between lens and source are dominated by the assessment of the angular radius of the source star and remain practically unaffected by lens binarity. Rather than judging the goodness-of-fit by means of a chi^2 test only, run tests provide useful additional information that can lead to the rejection of models and the detection of lens binarity in close-impact microlensing events.
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A comprehensive new approach is presented for deriving probability densities of physical properties characterizing lens or source that constitute an observed galactic microlensing event. While previously encountered problems are overcome,... more
A comprehensive new approach is presented for deriving probability densities of physical properties characterizing lens or source that constitute an observed galactic microlensing event. While previously encountered problems are overcome, constraints from event anomalies and model parameter uncertainties can be incorporated into the estimate. Probability densities for given events need to be carefully distinguished from the statistical distribution of the same parameters among the underlying population from which the actual lenses and sources are drawn. Using given model distributions of the mass spectrum, the mass density, and the velocity distribution of Galactic disk and bulge constituents, probability densities of lens mass, distance, and the effective lens-source velocities are derived, where the effect on the distribution that arises from additional observations of annual parallax or finite-source effects, or the absence of significant effects, is shown. The presented formalism can also be used to calculate probabilities for the lens to belong to one or another population and to estimate parameters that characterize anomalies. Finally, it is shown how detection efficiency maps for binary-lens companions in the physical parameters companion mass and orbital semi-major axis arise from values determined for the mass ratio and dimensionless projected separation parameter, including the deprojection of the orbital motion for elliptical orbits. Compared to the naive estimate based on 'typical values', the detection efficiency for low-mass companions is increased by mixing in higher detection efficiencies for smaller mass ratios (i.e. smaller masses of the primary).