Difference Image Analysis of Galactic Microlensing. I. Data Analysis

Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Griest, K.; Lehner, M. J.; Marshall, S.; Minniti, D.; Peterson, B. A.; Pratt, M. R.; Quinn, P. J.; Stubbs, C. W.; Sutherland, William J.; Tomaney, A.; Vandehei, T.; Welch, D. L.

doi:10.1086/307567

Cited by 54 publications

(53 citation statements)

References 23 publications

(41 reference statements)

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“…Their detection is based on the Difference Image Analysis technique (DIA, Alcock et al 1999a), which is sensitive to microlensing events on stars as faint as V = 23 mag, provided the peak magnification of these stars is brighter than V ∼ 21 mag. We computed the expected event rate for their average field (l = 2.7 • ,b = −3.3 • ) using the detection efficiency published in A00.…”

Section: Machomentioning

confidence: 99%

“…This is only feasible for fields with a sufficiently low extinction (A V < ∼ 2 mag) and requires sensitivity to magnitudes fainter than ∼21 mag. Fortunately, image subtraction methods are improving rapidly (Alard & Lupton 1998;Alcock et al 1999a;Alard 2000) and allow us to reach magnitudes down to V ∼ 23 because (1) crowding is virtually suppressed, (2) the micro-lensed star need not be pre-registered in a catalog and can be detected at any time provided the peak magnification makes it brighter than the detection limit. Detection of MW/Sgr events is thus already within the reach of current microlensing surveys.…”

Section: How To Detect Mw/sgr Events and Whymentioning

confidence: 99%

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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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Section: Machomentioning

confidence: 99%

Section: How To Detect Mw/sgr Events and Whymentioning

confidence: 99%

The Sagittarius dwarf galaxy as a microlensing target

Cseresnjes¹,

Alard²

2001

A&A

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“…Furthermore, even after taking all these into account, most of the stars will still contain some residual scatter due to uncured (or improperly considered) observational and environmental effects. Although a considerable filtering of these effects is possible with the aid of Differential Image Analysis (DIA, [4], or OIS, [2]), even this, more in-depth treatment cannot cure all remaining systematics ( [29]). Therefore, post-processing is an inevitable step in modern photometric surveys.…”

Section: Wide-field Photometric Surveys -The Overall Importancementioning

confidence: 99%

Synergies between exoplanet surveys and variable star research

Kovács

2017

EPJ Web Conf.

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Abstract. With the discovery of the first transiting extrasolar planetary system back in 1999, a great number of projects started to hunt for other similar systems. Because the incidence rate of such systems was unknown and the length of the shallow transit events is only a few percent of the orbital period, the goal was to monitor continuously as many stars as possible for at least a period of a few months. Small aperture, large field of view automated telescope systems have been installed with a parallel development of new data reduction and analysis methods, leading to better than 1% per data point precision for thousands of stars. With the successful launch of the photometric satellites CoRoT and Kepler, the precision increased further by one-two orders of magnitude. Millions of stars have been analyzed and searched for transits. In the history of variable star astronomy this is the biggest undertaking so far, resulting in photometric time series inventories immensely valuable for the whole field. In this review we briefly discuss the methods of data analysis that were inspired by the main science driver of these surveys and highlight some of the most interesting variable star results that impact the field of variable star astronomy.

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“…The main idea is to replace noisy wings of the Fourier transform with an analytical approximation [25]. After additional modifications, this approach has been successful applied in the regime of extreme blending (pixel lensing) to search for microlensing events in the direction of M31 [33], and to analyze the MACHO Galactic bulge microlensing data [4].…”

Section: Image Differencing Based On Psf Deconvolution With Fourier Dmentioning

confidence: 99%

Crowded Field Photometry and Difference Imaging

Woźniak¹

2008

Proceedings of the Manchester Microlensing Conference: The 12th International Conference and ANGLES Microlensing Workshop — PoS

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The purpose of this lecture is to introduce the basic methodology that enables massive high precision photometric monitoring of crowded fields in microlensing surveys. Some background is given on the development of techniques and tools that ultimately led to the adoption of the image differencing approach in a variety of projects in optical astronomy requiring time-series photometry. The effects of field crowding on photometry of individual sources and statistical properties of surveys are summarized. The discussion of photometric techniques starts from Point Spread Function (PSF) fitting in conventional crowded field codes, but the main focus is on difference imaging. The Alard & Lupton algorithm for image subtraction and PSF matching based on convolution is the corner stone of photometric data pipelines in the current generation microlensing surveys. The presentation covers a detailed description of the basic algorithm and its extension to kernels with strong gradients. To the extent possible, practical advice and performance comparisons are given to help implementers and users of the method.

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Difference Image Analysis of Galactic Microlensing. I. Data Analysis

Cited by 54 publications

References 23 publications

The Sagittarius dwarf galaxy as a microlensing target

The Sagittarius dwarf galaxy as a microlensing target

Synergies between exoplanet surveys and variable star research

Crowded Field Photometry and Difference Imaging

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