The MACHO Project: 45 Candidate Microlensing Events from the First Year Galactic Bulge Data

Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Griest, K.; Guern, J.; Lehner, M. J.; Marshall, S.; Park, H.-S.; Perlmutter, S.; Peterson, B. A.; Pratt, M. R.; Quinn, Peter J.; Rodgers, A. W.; Stubbs, C. W.; Sutherland, William J.

doi:10.1086/303851

Cited by 190 publications

(208 citation statements)

References 44 publications

(50 reference statements)

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“…Several observational campaigns have been set up to detect microlensing events in the direction of the Galactic bulge, e.g. MACHO (Alcock et al 1997), OGLE (Udalski et al 1994) and MOA (Sumi et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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Probing isolated compact remnants with microlensing

Sartore

Treves

2010

A&A

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Aims. We consider isolated compact remnants (ICoRs), i.e. neutrons stars and black holes that do not reside in binary systems and therefore cannot be detected as X-ray binaries. ICoRs may represent ∼5 percent of the stellar mass budget of the Galaxy, but they are very hard to detect. Here we explore the possibility of using microlensing to identify ICoRs. Methods. In a previous paper we described a simulation of neutron star evolution in phase space in the Galaxy, taking into account the distribution of the progenitors and the kick at formation. Here we first reconsider the evolution and distribution of neutron stars and black holes with an added a bulge component. From the new distributions we calculate the microlensing optical depth, event rate and distribution of event time scales, comparing and contrasting the case of ICoRs and "normal stars". Results. We find that the contribution of remnants to optical depth is slightly lower than without kinematics, owing to the evaporation from the Galaxy. On the other hand, the relative contribution to the rate of events is a factor ∼5 higher. In all, ∼6−7 percent of the events are likely related to ICoRs. In particular, ∼30−40 percent of the events with duration >100 days are possibly related to black holes. Conclusions. It seems therefore that microlensing observations are a suitable tool to probe the population of Galactic ICoRs.

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Section: Introductionmentioning

confidence: 99%

“…τ = 3.3 × 10 −6 (Udalski et al 1994) and τ = 3.9 × 10 −6 (Alcock et al 1997). To explain this discrepancy, Kiraga & Paczynski (1994) suggested that the Galactic bulge could give a substantial contribution to the optical depth and thus they included this contribution in their calculations.…”

Section: Introductionmentioning

confidence: 99%

Probing isolated compact remnants with microlensing

Sartore

Treves

2010

A&A

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“…More than ∼350 microlensing events detected towards the Galactic Centre have been published to date by several collaborations: MACHO (Alcock et al 1997b;Alcock et al 1999b;Alcock et al 2000, hereafter A00), OGLE Udalski et al 2000) and DUO (Alard & Guibert 1997). The resulting optical depth is > ∼ 3 10 −6 in Baade's window, a value that is higher than the theoretical expectation.…”

Section: Introductionmentioning

confidence: 99%

The Sagittarius dwarf galaxy as a microlensing target

Cseresnjes¹,

Alard²

2001

A&A

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Abstract. We estimate the optical depth, time-scale distribution and fraction of microlensing events originating from sources in the Sagittarius dwarf galaxy (Sgr) lensed by deflectors in the Milky Way. These events have a time-scale longer by a factor ∼1.3 than the MW/MW events and occur mainly on sources fainter than V ∼ 21 mag below Sgr's turn off. The fraction of events involving a source in Sgr depends on the location and extinction of the field and on the limiting magnitude of the survey. The contribution of the MW/Sgr events is negligible ( < ∼ 1%) at very low latitudes (|b| < ∼ 2 • ) but increases continuously towards higher |b| and becomes dominant near the highest density region of the dwarf galaxy. Sgr is present within the fields of current microlensing surveys and any optical depth map inferred from observations will become biased by the presence of Sgr towards higher |b| where the contribution of MW/Sgr events is significant. Systematic spectroscopic measurements on the sources of all the microlensing events may allow detection of this kind of event for which the degeneracy on the lens mass can be significantly reduced.

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“…The Massive Compact Halo Object (MACHO) project is a gravitational microlensing survey whose main goal was to find massive compact halo objects in the Milky Way halo to assess their mass contribution (Alcock et al 1997). Observations were made in the direction of the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC) and the Galactic Bulge.…”

Section: The Macho Surveymentioning

confidence: 99%

Automatic Survey-invariant Classification of Variable Stars

Benavente

Protopapas

Pichara

2017

ApJ

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Machine learning techniques have been successfully used to classify variable stars on widely-studied astronomical surveys. These datasets have been available to astronomers long enough, thus allowing them to perform deep analysis over several variable sources and generating useful catalogs with identified variable stars. The products of these studies are labeled data that enable supervised learning models to be trained successfully. However, when these models are blindly applied to data from new sky surveys their performance drops significantly. Furthermore, unlabeled data becomes available at a much higher rate than its labeled counterpart, since labeling is a manual and time-consuming effort. Domain adaptation techniques aim to learn from a domain where labeled data is available, the source domain, and through some adaptation perform well on a different domain, the target domain. We propose a full probabilistic model that represents the joint distribution of features from two surveys as well as a probabilistic transformation of the features between one survey to the other. This allows us to transfer labeled data to a study where it is not available and to effectively run a variable star classification model in a new survey. Our model represents the features of each domain as a Gaussian mixture and models the transformation as a translation, rotation and scaling of each separate component. We perform tests using three different variability catalogs: EROS, MACHO, and HiTS, presenting differences among them, such as the amount of observations per star, cadence, observational time and optical bands observed, among others.

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The MACHO Project: 45 Candidate Microlensing Events from the First Year Galactic Bulge Data

Cited by 190 publications

References 44 publications

Probing isolated compact remnants with microlensing

Probing isolated compact remnants with microlensing

The Sagittarius dwarf galaxy as a microlensing target

Automatic Survey-invariant Classification of Variable Stars

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