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M. Reid

Bio: M. Reid is an academic researcher from Victoria University of Wellington. The author has contributed to research in topics: Gravitational microlensing & Light curve. The author has an hindex of 14, co-authored 23 publications receiving 1656 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors describe observations carried out by the MOA group of the Galactic bulge during 2000 that were designed to detect efficiently gravitational microlensing of faint stars in which the magnification is high and/or of short duration.
Abstract: We describe observations carried out by the MOA group of the Galactic bulge during 2000 that were designed to detect efficiently gravitational microlensing of faint stars in which the magnification is high and/or of short duration. These events are particularly useful for studies of extrasolar planets and faint stars. Approximately 17 deg2 were monitored at a sampling rate of up to six times per night. The images were analysed in real time using a difference imaging technique. 20 microlensing candidates were detected, of which eight were alerted to the microlensing community whilst in progress. Approximately half of the candidates had high magnifications (≳10), at least one had very high magnification (≳50), and one exhibited a clear parallax effect. The details of these events are reported here, together with details of the on-line difference imaging technique. Some nova-like events were also observed and these are described, together with one asteroid.

505 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used Monte Carlo simulations to estimate the detection efficiency of microlensing event detection efficiency, where they constructed the I-band extinction map of their GB fields in order to find dereddened magnitudes.
Abstract: We analyze the data of the gravitational microlensing survey carried out by by the MOA group during 2000 towards the Galactic Bulge (GB). Our observations are designed to detect efficiently high magnification events with faint source stars and short timescale events, by increasing the the sampling rate up to 6 times per night and using Difference Image Analysis (DIA). We detect 28 microlensing candidates in 12 GB fields corresponding to 16 deg^2. We use Monte Carlo simulations to estimate our microlensing event detection efficiency, where we construct the I-band extinction map of our GB fields in order to find dereddened magnitudes. We find a systematic bias and large uncertainty in the measured value of the timescale $t_{\rm Eout}$ in our simulations. They are associated with blending and unresolved sources, and are allowed for in our measurements. We compute an optical depth tau = 2.59_{-0.64}^{+0.84} \times 10^{-6} towards the GB for events with timescales 0.3 10). These events are useful for studies of extra-solar planets.

233 citations

Journal ArticleDOI
TL;DR: In this article, the authors used Monte Carlo simulations to estimate the detection efficiency of microlensing event detection efficiency, where they constructed the I-band extinction map of their GB fields in order to find dereddened magnitudes.
Abstract: We analyze the data of the gravitational microlensing survey carried out by the Microlensing Observations in Astrophysics (MOA) group during 2000 toward the Galactic bulge (GB). Our observations are designed to detect efficient high-magnification events with faint source stars and short-timescale events, by increasing the sampling rate up to ~6 times per night and using Difference Image Analysis (DIA). We detect 28 microlensing candidates in 12 GB fields corresponding to 16 deg2. We use Monte Carlo simulations to estimate our microlensing event detection efficiency, where we construct the I-band extinction map of our GB fields in order to find dereddened magnitudes. We find a systematic bias and large uncertainty in the measured value of the timescale tE,out in our simulations. They are associated with blending and unresolved sources, and are allowed for in our measurements. We compute an optical depth τ = 2.59 × 10-6 toward the GB for events with timescales 0.3 10). These events are useful for studies of extrasolar planets.

210 citations

Journal ArticleDOI
TL;DR: In this article, the authors present an analysis of MACHO Alert 95-30, a dramatic microlensing event toward the Galactic bulge whose peak magnification departs significantly from the standard point-source micro-lensing model.
Abstract: We present analysis of MACHO Alert 95-30, a dramatic gravitational microlensing event toward the Galactic bulge whose peak magnification departs significantly from the standard point-source microlensing model Alert 95-30 was observed in real time by the Global Microlensing Alert Network (GMAN), which obtained densely sampled photometric and spectroscopic data throughout the event We interpret the light-curve fine structure as indicating transit of the lens across the extended face of the source star This signifies resolution of a star several kiloparsecs distant We find a lens angular impact parameter θmin/θsource = 0715 ± 0003 This information, along with the radius and distance of the source, provides an additional constraint on the lensing system Spectroscopic and photometric data indicate the source is a M4 III star of radius 61 ± 12 R☉, located on the far side of the bulge at ~9 kpc We derive a lens angular velocity, relative to the source, of 215 ± 29 km s-1 kpc-1, where the error is dominated by uncertainty in the angular size of the source star Likelihood analysis yields a median lens mass of 067 -->+ 253−046 M☉, located with 80% probability in the Galactic bulge at a distance of 693 -->+ 156−225 kpc If the lens is a main-sequence star, we can include constraints on the lens luminosity This modifies our estimates to Mlens=053 -->+ 052−035 M☉ and Dlens=657 -->+ 099−225 kpc Spectra taken during the event show that the absorption-line equivalent widths of Hα and the TiO bands near 6700 A vary, as predicted for microlensing of an extended source This is most likely due to center-to-limb variation in the stellar spectral lines The observed spectral changes further support our microlensing interpretation These data demonstrate the feasibility of using microlensing limb crossings as a tool to probe stellar atmospheres directly

168 citations

Journal ArticleDOI
TL;DR: In this article, the authors present an analysis of MACHO Alert 95-30, a dramatic gravitational microlensing event towards the Galactic bulge whose peak magnification departs significantly from the standard point-source micro-lensing model.
Abstract: We present analysis of MACHO Alert 95-30, a dramatic gravitational microlensing event towards the Galactic bulge whose peak magnification departs significantly from the standard point-source microlensing model. Alert 95-30 was observed in real-time by the Global Microlensing Alert Network (GMAN), which obtained densely sampled photometric and spectroscopic data throughout the event. We interpret the light-curve ``fine structure'' as indicating transit of the lens across the extended face of the source star. This signifies resolution of a star several kpc distant. We find a lens angular impact parameter theta_{min}/theta_{source} = 0.715 +/- 0.003. This information, along with the radius and distance of the source, provides an additional constraint on the lensing system. Spectroscopic and photometric data indicate the source is an M4 III star of radius 61 +/- 12 Rsun, located on the far side of the bulge at 9 kpc. We derive a lens angular velocity, relative to the source, of 21.5 +/- 4.9 km/s/kpc, where the error is dominated by uncertainty in the source radius. Likelihood analysis yields a median lens mass of 0.67{+2.53}{-0.46} Msun, located with 80% probability in the Galactic bulge at a distance of 6.93{+1.56}{-2.25} kpc. If the lens is a main-sequence star, we can include constraints on the lens luminosity. This modifies our estimates to M_lens = 0.53{+0.52}{-0.35} Msun and D_lens = 6.57{+0.99}{-2.25} kpc. Spectra taken during the event show that the absorption line equivalent widths of H alpha and the TiO bands near 6700 A vary, as predicted for microlensing of an extended source. This is most likely due to center-to-limb variation in the stellar spectral lines. These data demonstrate the feasibility of using microlensing limb crossings as a tool to probe stellar atmospheres directly.

148 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, it was shown that most long-duration soft-spectrum gamma-ray bursts are accompanied by massive stellar explosions (GRB-SNe) and that most of the energy in the explosion is contained in nonrelativistic ejecta (producing the supernova) rather than in the relativistic jets responsible for making the burst and its afterglow.
Abstract: Observations show that at least some gamma-ray bursts (GRBs) happen simultaneously with core-collapse supernovae (SNe), thus linking by a common thread nature's two grandest explosions. We review here the growing evidence for and theoretical implications of this association, and conclude that most long-duration soft-spectrum GRBs are accompanied by massive stellar explosions (GRB-SNe). The kinetic energy and luminosity of well-studied GRB-SNe appear to be greater than those of ordinary SNe, but evidence exists, even in a limited sample, for considerable diversity. The existing sample also suggests that most of the energy in the explosion is contained in nonrelativistic ejecta (producing the supernova) rather than in the relativistic jets responsible for making the burst and its afterglow. Neither all SNe, nor even all SNe of Type Ibc produce GRBs. The degree of differential rotation in the collapsing iron core of massive stars when they die may be what makes the difference.

1,389 citations

Journal ArticleDOI
TL;DR: In this article, the interplay between these observations and theoretical models of the prompt gamma-ray burst and its afterglow is reviewed, and a model of the burst's origin and mechanism is proposed.
Abstract: Gamma-ray bursts are the most luminous explosions in the Universe, and their origin and mechanism are the focus of intense research and debate. More than three decades after their discovery, and after pioneering breakthroughs from space and ground experiments, their study is entering a new phase with the recently launched Swift satellite. The interplay between these observations and theoretical models of the prompt gamma-ray burst and its afterglow is reviewed.

1,294 citations

Journal ArticleDOI
TL;DR: The formation and evolution of galaxies is one of the great outstanding problems of astrophysics as discussed by the authors, and a detailed physical picture where individual stellar populations can be associated with (tagged to) elements of the protocloud is far beyond our current understanding.
Abstract: ▪ Abstract The formation and evolution of galaxies is one of the great outstanding problems of astrophysics. Within the broad context of hierachical structure formation, we have only a crude picture of how galaxies like our own came into existence. A detailed physical picture where individual stellar populations can be associated with (tagged to) elements of the protocloud is far beyond our current understanding. Important clues have begun to emerge from both the Galaxy (near-field cosmology) and the high redshift universe (far-field cosmology). Here we focus on the fossil evidence provided by the Galaxy. Detailed studies of the Galaxy lie at the core of understanding the complex processes involved in baryon dissipation. This is a necessary first step toward achieving a successful theory of galaxy formation.

1,128 citations

Journal ArticleDOI
TL;DR: The EROS-2 project was designed to test the hypothesis that massive compact halo objects (the so-called ''machos'') could be a major component of the dark matter halo of the Milky Way galaxy.
Abstract: The EROS-2 project was designed to test the hypothesis that massive compact halo objects (the so-called ''machos'') could be a major component of the dark matter halo of the Milky Way galaxy. To this end, EROS-2 monitored millions of stars in the Magellanic clouds for microlensing events caused by such objects. (abridged)

908 citations

Journal ArticleDOI
TL;DR: The cosmological gamma-ray burst (GRB) phenomenon is reviewed in this article, where broad observational facts and empirical phenomenological relations of the GRB prompt emission and afterglow are outlined.
Abstract: The cosmological gamma-ray burst (GRB) phenomenon is reviewed. The broad observational facts and empirical phenomenological relations of the GRB prompt emission and afterglow are outlined. A well-tested, successful fireball shock model is introduced in a pedagogical manner. Several important uncertainties in the current understanding of the phenomenon are reviewed, and prospects of how future experiments and extensive observational and theoretical efforts may address these problems are discussed.

812 citations