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1

Light Curves of Symbiotic Stars in Massive Photometric Surveys I: D-Type Systems

Gromadzki M., Mikołajewska J., Whitelock P., Marang F.

Acta Astronomica

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2009

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Vol. 59, No. 2

169--191

EN

ASAS, MACHO, OGLE and SAAO JHKL light curves of 13 stars, that have at some time been classified as D-type symbiotic stars, are analyzed. Most of the near-IR light curves that have been monitored over many years show long-term changes due to variable dust obscuration, in addition to the stellar pulsation. The distances to these objects are derived from the period-luminosity relation and estimates of the mass-loss rates made from the K0-[12] color. We reclassify AS 245 as an S-type symbiotic star with a semi-regular cool component and a pulsation period of about one year. The periods of the large amplitude pulsations of SS73 38 (463 days), AS 210 (423 days) and H2-38 (395 days) are estimated for the first time, confirming that they are symbiotic Miras. A comparison of the symbiotic Miras with normal Miras of similar pulsation period shows that the symbiotic stars have on average higher values of K0-[12]. This may indicate that they have higher mass-loss rates, or more likely that the dust which is being lost by the Mira is trapped within the binary system.

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

New Variable Stars on Digitized Moscow Collection Plates. Field 66 Ophiuchi (Northern Half)

Kolesnikova D. M., Sat L. A., Sokolovsky K. V., Antipin S. V., Samus N. N.

Acta Astronomica

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2008

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Vol. 58, No. 3

279--292

EN

We initiated digitization of the Moscow collection of astronomical plates using flatbed scanners. Techniques of photographic photometry of the digital images were applied, enabling an effective search for new variable stars. Our search for new variables among 140 000 stars in the 10°×5° northern half of the field centered at 66 Oph, photographed with the Sternberg Institute's 40-cm astrograph in 1976-1995, gave 274 new discoveries, among them: 2 probable Population II Cepheids, 81 eclipsing variables, 5 high-amplitude δ Sct stars (HADSs), 82 RR Lyr stars, 62 red irregular variables and 41 red semiregular stars, 1 slow irregular variable not red in color. Ephemerides were determined for periodic variable stars. We detected about 30 variability suspects for follow-up CCD observations, confirmed 11 stars from the New Catalog of Suspected Variable Stars, and derived new ephemerides for 2 stars already contained in the General Catalog of Variable Stars.

7

Variable Star Census in CoRoT "Eyes"

Benkö J. M., Csubry Z.

Acta Astronomica

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2007

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Vol. 57, No. 1

73--85

EN

A complete catalog of variable stars in the possible observing areas ("eyes") of the CoRoT satellite is presented. All known data sources were cross-correlated and compiled confirming the variability of 81 stars formerly known as suspected variables. By means of the TiFrAn program package a comprehensive variability search was carried out on the NSVS (ROTSE-I) database for the first time in these regions. This search has demonstrated the effectiveness of TiFrAn as a tool for finding and analyzing variable stars in big databases. Our catalog contains 4925 variable stars of which 1396 stars are new discoveries. Also appended is a list of 198 suspected variable stars.

8

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.