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1

Finding the Brightest Galactic Bulge Microlensing Events with a Small Aperture Telescope and Image Subtraction

Nataf D. M., Stanek K. Z., Bakos G. A.

Acta Astronomica

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2009

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Vol. 59, No. 3

255--272

EN

Following the suggestion of Gould and Depoy (1998) we investigate the feasibility of studying the brightest microlensing events towards the Galactic bulge using a small aperture (≈10 cm) telescope. We used one of the HAT telescopes to obtain 151 exposures spanning 88 nights in 2005 of an 8°4×8°4 FOV centered on (l,b)=(2.85, -5.00). We reduced the data using image subtraction software. We find that such a search method can effectively contribute to monitoring bright microlensing events, as was advocated. Comparing this search method to the existing ones we find a dedicated bulge photometric survey of this nature would fulfill a significant niche at excellent performance and rather low cost. We obtain matches to 7 microlensing events listed in the 2005 OGLE archives. We find several other light curves whose fits closely resemble microlensing events. Unsurprisingly, many periodic variable stars and miscellaneous variable stars are also detected in our data, and we estimate approximately 50% of these are new discoveries. We conclude by briefly proposing Small Aperture Microlensing Survey, which would monitor the Galactic bulge around the clock to provide dense coverage of the highest magnification microlensing events.

2

XROM and RCOM: Two New OGLE-III Real Time Data Analysis Systems

Udalski A.

Acta Astronomica

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2008

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Vol. 58, No. 3

187--192

EN

We describe two new OGLE-III real time data analysis systems: XROM and RCOM. The XROM system has been designed to provide continuous real time photometric monitoring of the optical counterparts of X-ray sources while RCOM system provides real time photometry of R Coronae Borealis variable stars located in the OGLE-III fields. Both systems can be used for triggering follow-up observations in crucial phases of variability episodes of monitored objects.

3

The Optical Gravitational Lensing Experiment. OGLE-III Photometric Maps of the Large Magellanic Cloud

Udalski A., Soszyński I., Szymański M. K., Kubiak M., Pietrzyński G., Wyrzykowski L., Szewczyk O., Ulaczyk K., Poleski R.

Acta Astronomica

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2008

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Vol. 58, No. 2

89--102

EN

We present the OGLE-III Photometric Maps of the Large Magellanic Cloud. They cover about 40 square degrees of the LMC and contain mean, calibrated VI photometry and astrometry of about 35 million stars observed during seven observing seasons of the third phase of the Optical Gravitational Lensing Experiment - OGLE-III. We discuss the quality of data and present color-magnitude diagrams of selected fields. The OGLE-III Photometric Maps of the LMC are available to the astronomical community from the OGLE Internet archive.

4

The Optical Gravitational Lensing Experiment. OGLE-III Photometric Maps of the Small Magellanic Cloud

Udalski A., Soszyński I., Szymański M. K., Kubiak M., Pietrzyński G., Wyrzykowski Ł., Szewczyk O., Ulaczyk K., Poleski R.

Acta Astronomica

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2008

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Vol. 58, No. 4

329--343

EN

We present OGLE-III Photometric Maps of the Small Magellanic Cloud. They contain precise, calibrated VI photometry of about 6.2 million stars from 41 OGLE-III fields in the SMC observed regularly in the years 2001-2008 and covering about 14 square degrees in the sky. Also precise astrometry of these objects is provided. One of the fields, SMC140, is centered on the 47 Tucanae Galactic globular cluster providing unique data on this object. We discuss quality of the data and present a few color-magnitude diagrams of the observed fields. All photometric data are available to the astronomical community from the OGLE Internet archive.

5

The Optical Gravitational Lensing Experiment. Final Reductions of the OGLE-III Data

Udalski A., Szymański M. K., Soszyński I., Poleski R.

Acta Astronomica

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2008

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Vol. 58, No. 2

69--87

EN

We describe methods applied to the final photometric reductions and calibrations to the standard system of the images collected during the third phase of the Optical Gravitational Lensing Experiment survey - OGLE-III. Astrometric reduction methods are also presented. The OGLE-III data constitute a unique data set covering the Magellanic Clouds, Galactic bulge and Galactic disk fields monitored regularly every clear night since 2001 and being significant extension and continuation of the earlier OGLE observations. With the earlier OGLE-II and OGLE-I photometry some of the observed fields have now 16-year long photometric coverage.

6

Toward the Detection of Transiting Hot Earths and Hot Neptunes in Open Clusters

Pepper J., Gaudi B. S.

Acta Astronomica

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2006

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Vol. 56, No. 2

183--197

EN

Radial velocity searches for extrasolar planets have recently detected several very low mass (7-20 Msolar) planets in close orbits with periods ≤10 days. We consider the prospects for detecting the analogs of these planets in Galactic open clusters via transits. We outline the requirements for constructing a transit survey that would allow one to probe such "Hot Earths" and "Hot Neptunes." Specifically, we present a simple criterion for detection that defines the minimum aperture required to detect planets of a given radius in a cluster at a given distance. Adopting photometric precisions that have been demonstrated in state-of-the-art variability surveys, we then predict the number of planets one could potentially detect with ambitious transit surveys toward several open clusters. Dedicated surveys lasting more than 20 nights with Pan-STARRS toward the Hyades and Praesepe could detect a handful of Hot Earths, if the majority of stars host such planets. Similar surveys with larger aperture telescopes (e.g., CFHT, MMT), toward M 67, M 35, M 50, and M 37 could detect Hot Neptunes, provided that their frequency is ≥1%. The majority of planets will be detected around M dwarfs; detecting Hot Neptunes around such primaries requires photometric precisions of ≈1%, whereas Hot Earths require ≈0.1%. We discuss potential hurdles in detecting and confirming small planets in ground-based surveys, including correlated noise, false positives, and intrinsic stellar variability.