PL
 |
EN
Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl
Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 98

Liczba wyników na stronie
first rewind previous Strona / 5 next fast forward last
Wyniki wyszukiwania
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 5 next fast forward last
1
Content available remote Erratum: The Optical Gravitational Lensing Experiment. Multiple Cluster Candidates in the Small Magellanic Cloud
100%
Pietrzyński G. , Udalski A.
Acta Astronomica
|
1999
|
tom Vol. 49, No. 3
433--434
EN
In the paper "The Optical Gravitational Lensing Experiment. Multiple Cluster Candidates in the Small Magellanic Cloud" (Acta Astron., 49, p. 165) several entries in Tables 1 and 2 have wrong coordinates and sizes due to computer code error. Corrected versions of Tables 1 and 2 appear below.
2
Content available remote The Optical Gravitational Lensing Experiment. Multiple Cluster Candidates in the Small Magellanic Cloud
100%
Pietrzyński G. , Udalski A.
Acta Astronomica
|
1999
|
tom Vol. 49, No. 2
165--169
EN
We present the list of potential multiple star clusters from the central part of the SMC. Presented systems were selected from the catalog of star clusters from the SMC. We find 23 suspected cluster pairs and 4 triple systems. The statistical analysis suggests that many of them may constitute physical systems. Size, equatorial coordinates and age of presented clusters are given. Age of clusters which form five pairs and one triple system is coeval suggesting common origin of these objects.
3
Content available remote The Optical Gravitational Lensing Experiment. Multiple Cluster Candidates in the Large Magellanic Cloud
100%
Pietrzyński G. , Udalski A.
Acta Astronomica
|
2000
|
tom Vol. 50, No. 3
355--367
EN
We present 100 multiple cluster candidates selected from the OGLE catalog of star clusters in the Large Magellanic Cloud. Statistical analysis shows that the significant fraction of these objects may constitute physical systems. Coeval ages of 102 components of multiple objects suggest their common origin. 53 components have very different ages. The comparison of the population of multiple clusters candidates from the SMC and the LMC shows that: a) distributions of sizes and ages of multiple and single clusters from the Magellanic Clouds are very similar, b) the difference of sizes of components of a given system is small, c) in both distributions of separation of multiple clusters from the LMC and SMC two peaks are seen at about 9 pc and 15 pc, d) both age distributions reveal peaks around 100 Myr, which may be connected with the last encounter of the LMC and the SMC.
4
Content available remote The Optical Gravitational Lensing Experiment. Age of Star Clusters from the SMC
100%
Pietrzyński G. , Udalski A.
Acta Astronomica
|
1999
|
tom Vol. 49, No. 2
157--164
EN
We present determination of age of clusters from 2.4 square degree region of the SMC bar. The photometric data were taken from the BVI maps of the SMC and catalog of clusters in this galaxy obtained during the OGLE-II microlensing survey. For 93 well populated SMC clusters their age is derived with the standard procedure of isochrone fitting. The distribution of age of cluster from the SMC is presented. It indicates either non-uniform process of cluster formation or very effective disruption of clusters.
5
Content available remote The Optical Gravitational Lensing Experiment. Ages of about 600 Star Clusters from the LMC
100%
Pietrzyński G. , Udalski A.
Acta Astronomica
|
2000
|
tom Vol. 50, No. 3
337--354
EN
We present results of age determination based on the standard procedure of isochrone fitting for about 600 star clusters younger than about 1.2 Gyr from the central parts of the LMC. Comparison of age distributions of star clusters from the LMC and the SMC shows that cluster formation histories are different in these galaxies. The age distribution of the LMC clusters reveals bursty nature of cluster formation in this galaxy, with contrast to the relatively uniform distribution of cluster ages in the SMC. We detected three extended peaks in the distribution of ages of LMC clusters, located at about 7 Myr, 125 Myr and 0.8 Gyr. All detected peaks have complex structure. While the structure of the youngest and the oldest peaks may be spurious due to accuracy of age determination, in the middle peak two evident sub-peaks at 100 Myr and 160 Myr are clearly seen. Similar peaks are seen in the distribution of ages of clusters from the SMC, which indicates that increased cluster formation ratio during these periods might be caused by the last encounter between the Magellanic Clouds. The sample of clusters from the LMC is overabundant in very young (<10 Myr) and old (>400 Myr) clusters, and underabundant in clusters having ages in the range from 80 to 15 Myr with respect to the studied sample of clusters from the SMC.
6
Content available remote Erratum: The Optical Gravitational Lensing Experiment. Age of Star Clusters from the SMC
100%
Pietrzyński G. , Udalski A.
Acta Astronomica
|
1999
|
tom Vol. 49, No. 3
435--436
EN
In the paper "The Optical Gravitational Lensing Experiment. Age of Star Clusters from the SMC" (Acta Astron., 49, p. 157) several entries in Table 1 have wrong coordinates and sizes due to computer code error. Corrected version of Table 1 appears below.
7
Content available remote The Optical Gravitational Lensing Experiment. Variable Stars in Star Clusters of the Magellanic Clouds. I. Eclipsing Systems in the Clusters of the SMC
100%
Pietrzyński G. , Udalski A.
Acta Astronomica
|
1999
|
tom Vol. 49, No. 2
149--155
EN
The list of 127 eclipsing stars in optical coincidence with star clusters from the SMC is presented. It was prepared using the catalogs of eclipsing systems and star clusters from the SMC based on observations collected during the OGLE-II microlensing project. Location of 12 eclipsing stars in the color-magnitude diagram of clusters allows to exclude their membership. Photometric data of 73 systems support their membership. The remaining 42 objects were found in loose, faint clusters and therefore no conclusive statement about their membership can be made. All presented data are available from the OGLE archive.
8
Content available remote The Optical Gravitational Lensing Experiment. Cepheids in Star Clusters from the Magellanic Clouds
100%
Pietrzyński G. , Udalski A.
Acta Astronomica
|
1999
|
tom Vol. 49, No. 4
543--550
EN
We present Cepheids located in the close neighborhood of star clusters from the Magellanic Clouds. 204 and 132 such stars were found in the LMC and SMC, respectively. The lists of objects were constructed based on catalogs of Cepheids and star clusters, recently published by the OGLE-II collaboration. Location of selected Cepheids on the sky indicates that many of them are very likely cluster members. Photometric data of Cepheids and clusters are available from the OGLE Internet archive.
9
Content available remote Variable Stars in the Field of Young Open Cluster NGC 659
80%
Pietrzyński G. , Wyrzykowski Ł. , Szewczyk O. , Bielewicz M.
Acta Astronomica
|
2001
|
tom Vol. 51, No. 1
65--74
EN
We present results of the search for variable stars in young open cluster NGC 659. Based on 35 nights of observations, 7 new variable stars were discovered. Three of them are Be stars. Another three are most probably pulsating variables of γ Dor type. One star is a detached binary system.
10
Content available remote Variable Stars in the Field of Young Open Cluster NGC 581
80%
Wyrzykowski Ł. , Pietrzyński G. , Szewczyk O.
Acta Astronomica
|
2002
|
tom Vol. 52, No. 1
105--114
EN
We present results of the search for variable stars in the field of young open cluster NGC 581. Based on 19 nights of observations, 6 new variable stars were discovered. Two of them turned out to be eclipsing binary systems. Another two detected variable stars are most probably of γ Dor type. During our observations one of the known Be stars located in our field of view showed irregular variations of brightness, typical for this class of stars. The sixth variable star is a pulsating red giant.
11
Content available remote The Optical Gravitational Lensing Experiment. A CCD Search for Variable Stars in Open Clusters - NGC 5999
80%
Pietrzyński G. , Kubiak M. , Udalski A. , Szymański M.
Acta Astronomica
|
1998
|
tom Vol. 48, No. 3
489--508
EN
We report discovery of 41 variable stars in the field of the young open cluster NGC 5999. 30 stars have light curves typical for eclipsing systems: this group contains three Algol-type and 27 W UMa type variable stars. One RR Lyr and one δ Scuti stars form a group of pulsating variables. Nine variable stars are of unknown type and classified as miscellaneous. One of them is a periodic, most probably chromospherically active star. Our data are too scarce to make any conclusion about periodicity of remaining eight variable stars.
12
Content available remote The Araucaria Project: The Distance to the Small Magellanic Cloud from Near Infrared Photometry of Type II Cepheids
71%
Ciechanowska A. , Pietrzyński G. , Szewczyk O. , Gieren W. , Soszyński I.
Acta Astronomica
|
2010
|
tom Vol. 60, No. 3
233--243
EN
We have obtained deep near infrared J- and K-band observations of 14 BL Her and 5 W Vir SMC stars from the OGLE-III survey with the ESO New Technology Telescope equipped with the SOFI infrared camera. From these observations, period-luminosity (P-L) relations in the J and Ks 2MASS bands were derived. The slopes of the K- and J-band relations of -2.15±0.19 and -1.95±0.24, respectively, agree very well with the corresponding slopes derived previously for population II Cepheids in globular clusters, Galactic bulge and in the Large Magellanic Cloud. The distance modulus to the SMC obtained from our data using P-L relation derived for globular cluster Cepheids equals to 18.85±0.07 (statistical) ± 0.07 mag (systematic without including potential metallicity effect), which within the uncertainties agrees well with the results obtained with other methods.
13
Content available remote The Optical Gravitational Lensing Experiment. Catalog of Microlensing Events in the Galactic Bulge
61%
Udalski A. , Żebruń K. , Szymański M. , Kubiak M. , Pietrzyński G. , Soszyński I. , Woźniak P.
Acta Astronomica
|
2000
|
tom Vol. 50, No. 1
1--65
EN
We present the Catalog of microlensing events detected toward the Galactic bulge in three observing seasons, 1997-1999, during the OGLE-II microlensing survey. The search for microlensing events was performed using a database of about 4×109 photometric measurements of about 20.5 million stars from the Galactic bulge. The Catalog comprises 214 microlensing events found in the fields covering about 11 square degrees on the sky and distributed in different parts of the Galactic bulge. The sample includes 20 binary microlensing events, 14 of them are caustic crossing. In one case a double star is likely lensed. We present distribution of the basic parameters of microlensing events and show preliminary rate of microlensing in different regions of the Galactic bulge. The latter reveals clear dependence on the Galactic coordinates. The dependence on l indicates that the majority of lenses toward the Galactic bulge are located in the Galactic bar. Models of the Galactic bar seem to reasonably predict the observed spatial distribution of microlensing events in the Galactic bulge. All data presented in the Catalog and photometry of all events are available from the OGLE Internet archive.
14
Content available remote The Optical Gravitational Lensing Experiment. Eclipsing Binary Stars in the Small Magellanic Cloud
61%
Udalski A. , Soszyński I. , Szymański M. , Kubiak M. , Pietrzyński G. , Woźniak P. , Żebruń K.
Acta Astronomica
|
1998
|
tom Vol. 48, No. 4
563--651
EN
We present the catalog of 1459 eclipsing binary stars detected in the central 2.4 square degree area of the Small Magellanic Cloud during the OGLE-II microlensing search. The sample includes objects brighter than I≈20 mag with periods ranging from about 0.3 to 250 days. The average completeness of the catalog is about 80%. Statistics of the entire sample and well detached systems, suitable for distance determination, are also presented. The catalog, finding charts and BVI photometry data for all objects are available from the OGLE Internet archive.
15
Content available remote The Optical Gravitational Lensing Experiment. Variable Stars in the Field of Open Cluster NGC 6259
61%
Ciechanowska A. , Pietrzyński G. , Wyrzykowski Ł. , Szewczyk O. , Kubiak M. , Udalski A. , Szymański M. K.
Acta Astronomica
|
2006
|
tom Vol. 56, No. 2
219--236
EN
We present the results of a search for variable stars in the field of NGC 6259. Altogether 85 variable stars have been discovered. 36 of them are eclipsing systems. This group contains 13 EA, 2 EB and 21 EW-type stars. Light curves of two variable stars resemble those of Miras. The remaining 47 variable stars detected in the field of this open cluster are most probably highly obscured red giants (OSARG, irregular). For all detected variable stars we provide their light curves, preliminary classification, discussion on the possible cluster membership, equatorial coordinates, finding charts and periods when possible.
16
Content available remote The Optical Gravitational Lensing Experiment. BVI Maps of Dense Stellar Regions. I. The Small Magellanic Cloud
61%
Udalski A. , Szymański M. , Kubiak M. , Pietrzyński G. , Woźniak P. , Żebruń K.
Acta Astronomica
|
1998
|
tom Vol. 48, No. 2
147--174
EN
We present three color, BVI maps of the Small Magellanic Cloud. The maps contain precise photometric and astrometric data for about 2.2 million stars from the central regions of the SMC bar covering ≈2.4 square degrees on the sky. Mean brightness of stars is derived from observations collected in the course of the OGLE-II microlensing search from about 130, 30 and 15 measurements in the I, V and B-bands, respectively. Accuracy of the zero points of photometry is about 0.01 mag, and astrometry 0.15 arcsec (with possible systematic error up to 0.7 arcsec). Color-magnitude diagrams of observed fields are also presented. The maps of the SMC are the first from the series of similar maps covering other OGLE fields: LMC, Galactic bulge and Galactic disk. The data are very well suited for many projects, particularly for the SMC which has been neglected photometrically for years. Because of potentially great impact on many astrophysical fields we decided to make the SMC data available to the astronomical community from the OGLE Internet archive.
17
Content available remote The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. IV. Catalog of Cepheids from the Large Magellanic Cloud
61%
Udalski A. , Soszyński I. , Szymański M. , Kubiak M. , Pietrzyński G. , Woźniak P. , Żebruń K.
Acta Astronomica
|
1999
|
tom Vol. 49, No. 3
223--317
EN
We present the Catalog of Cepheids from the LMC. The Catalog contains 1333 objects detected in the 4.5 square degree area of central parts of the LMC. About 3.4×105 BVI measurements of these stars were collected during the OGLE-II microlensing survey. The Catalog data include period, BVI photometry, astrometry, and R21, φ21 parameters of the Fourier decomposition of I-band light curve. The vast majority of objects from the Catalog are the classical Cepheids pulsating in the fundamental or first overtone mode. The remaining objects include Population II Cepheids and red giants with pulsation-like light curves. Tests of completeness performed in overlapping parts of adjacent fields indicate that completeness of the Catalog is very high: >96%. Statistics and distributions of basic parameters of Cepheids are also presented. Finally, we show the light curves of three eclipsing systems containing Cepheid detected among objects of the Catalog. All presented data, including individual BVI observations are available from the OGLE Internet archive.
18
Content available remote Difference Image Analysis of the OGLE-II Bulge Data. III. Catalog of 200 000 Candidate Variable Stars
61%
Woźniak P. R. , Udalski A. , Szymański M. , Kubiak M. , Pietrzyński G. , Soszyński I. , Żebruń K.
Acta Astronomica
|
2002
|
tom Vol. 52, No. 2
129--142
EN
We present the first edition of a catalog of variable stars from OGLE-II Galactic bulge data covering 3 years: 1997-1999. Typically 200-300 I band data points are available in 49 fields between -11 and 11 degrees in galactic longitude, totaling roughly 11 square degrees in sky coverage. Photometry was obtained using the Difference Image Analysis (DIA) software and tied to the OGLE data base with the DoPhot package. The present version of the catalog comprises 221 801 light curves. In this preliminary work the level of contamination by spurious detections is still about 10%. Parts of the catalog have only crude calibration, insufficient for distance determinations. The next, fully calibrated, edition will include the data collected in year 2000. The data is accessible via ftp. Due to the data volume, we also distribute DAT tapes upon request.
19
Content available remote Optical Gravitational Lensing Experiment. The Catalog of Clusters in the Small Magellanic Cloud
61%
Pietrzyński G. , Udalski A. , Kubiak M. , Szymański M. , Woźniak P. , Żebruń K.
Acta Astronomica
|
1998
|
tom Vol. 48, No. 2
175--268
EN
We present the catalog of clusters found in the area of ≈2.4 square degree in the central regions of the Small Magellanic Cloud. The catalog contains data for 238 clusters, 72 of them are new objects. For each cluster equatorial coordinates, radii, approximate number of members, cross-identification, finding chart and color magnitude diagrams: V-(B-V) and V-(V-I) are provided. Photometric data for all clusters presented in the catalog are available from the OGLE Internet archive.
20
Content available remote The Optical Gravitational Lensing Experiment. Photometry of the MACHO-SMC-98-1 Binary Microlensing Event
61%
Udalski A. , Kubiak M. , Szymański M. , Pietrzyński G. , Woźniak P. , Żebruń K.
Acta Astronomica
|
1998
|
tom Vol. 48, No. 3
431--438
EN
We present photometry of the unique binary microlensing event MACHO-SMC-98-1 collected by the OGLE group. Particularly interesting observation was made close to the first caustic crossing which was not covered by observations of other groups. It allows to test proposed models of which Model 1 proposed by PLANET group seems to be in the best agreement with the OGLE observations.
first rewind previous Strona / 5 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.