The Optical Gravitational Lensing Experiment. The Catalog of Clusters in the Small Magellanic Cloud

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.Comment: 15 pages, Latex, 2 Figures, Appendix (only one page of the Appendix, in jpg format, is included. Full distribution of the Catalog is available from http://www.astrouw.edu.pl/~ftp/ogle or http://www.astro.princeton.edu/~ogle) Accepted for publication in Acta Astronomica 1998, 48, 175. Corrected address of the OGLE Internet archiv

Optical Gravitational Lensing Experiment. Distance to the Magellanic Clouds with the Red Clump Stars: Are the Magellanic Clouds 15% Closer than Generally Accepted?

We present a new distance determination to the Large and Small Magellanic Clouds using the newly developed red clump stars method (Paczynski and Stanek 1998). This new, single-step, Hipparcos calibrated method seems to be one of the most precise techniques of distance determination with very small statistical error due to large number of red clump stars usually available. The distances were determined independently along four lines-of-sight located at opposite sides of each Magellanic Cloud. The results for each line-of-sight are very consistent. For the SMC we obtain the distance modulus: m-M=18.56+/-0.03+/-0.06 mag (statistical and systematic errors, respectively) and for the LMC: m-M=18.08+/-0.03+/-0.12} mag where systematic errors are mostly due to uncertainty in reddening estimates. Both distances will be refined and systematic errors reduced when accurate reddening maps for our fields are available. Distance moduli to both Magellanic Clouds are ~0.4 mag smaller than generally accepted values. The modulus to the LMC is in good agreement with the recent determinations from RR Lyrae type stars and upper limit resulting from the SN1987A echo. We suspect that the distance to the LMC and SMC is shorter by about 15% than previously assumed: 42 kpc and 52 kpc, respectively. We also present our color-magnitude diagrams around the red clump for the LMC and SMC. We identify vertical red clump, first noted by Zaritsky and Lin (1997), in the color-magnitude diagram of both Magellanic Clouds and we interpret it as an evolutionary feature rather than unknown stellar population between the LMC and our Galaxy.Comment: 16 pages, Latex, 5 Figures (Fig.2 and 3 - jpg images). Revised version, accepted for publication in Acta Astronomica Vol. 4

The Optical Gravitational Lensing Experiment. Catalog of Star Clusters from the Large Magellanic Cloud

We present the catalog of star clusters found in the area of about 5.8 square degree in the central regions of the Large Magellanic Cloud. It contains data for 745 clusters. 126 of them are new objects. For each cluster equatorial coordinates, radius, approximate number of members and cross-identification are provided. Photometric data for all clusters presented in the catalog and Atlas consisting of finding charts and color-magnitude diagrams are available electronically from the OGLE Internet archive.Comment: 20 pages, Latex. Only one page of the Appendix is included. Full distribution of the Catalog is available from http://www.astrouw.edu.pl/~ogle or http://www.astro.princeton.edu/~ogle) Acta Astronomica submitte

The Optical Gravitational Lensing Experiment. BVI Maps of Dense Stellar Regions. I. The Small Magellanic Cloud

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.Comment: 17 pages, Latex+psfig, 16 Figures (Figs. 1 and 6-9 - jpg images, Figs. 10-16 not available electronically). Accepted for publication in Acta Astronomica 1998, 48, 147. Corrected address of the OGLE Internet archiv

Optical Gravitational Lensing Experiment. Photometry of the MACHO-SMC-1 Microlensing Candidate

We present photometric observations of the MACHO-SMC-1 microlensing candidate collected by the OGLE-2 project. We show light curves of both components of the 1.6 arcsec blend: microlensed star and its optical companion. We find the contribution of the optical companion to the total flux to be 24% and confirm presence of the small amplitude periodic oscillations in the light curve of the lensed star with the period of 5.096 days and amplitude 0.05 mag. The lensed star is probably an ellipsoidal binary system.Comment: 5 pages, Latex, 4 Figures. Submitted to Acta Astronomic

The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. IV. Catalog of Cepheids from the Large Magellanic Cloud

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*10^5 BVI measurements of these stars were collected during the OGLE-II microlensing survey. The Catalog data include period, BVI photometry, astrometry, and R_21, \phi_21 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.Comment: 23 pages, Latex+psfig. Fig. 1 and Appendices (only one page) in JPG format. Acta Astronomica 49, 223. Full resolution Figure 1, all Appendices and the entire Catalog are available from the OGLE Internet archive: http://www.astrouw.edu.pl/~ftp/ogle or its US mirror http://www.astro.princeton.edu/~ogle Revised (journal) version, minor change

The Optical Gravitational Lensing Experiment. BVI Maps of Dense Stellar Regions. II. The Large Magellanic Cloud

We present the BVI photometric maps of the Large Magellanic Cloud. They contain BVI photometry and astrometry of more than 7 million stars from the central parts of the LMC. The data were collected during the second phase of the OGLE microlensing project. We discuss the accuracy of the data and present color-magnitude diagrams of all 26 fields observed by OGLE in the LMC. The BVI maps of the LMC are accessible electronically for the astronomical community from the OGLE Internet archive.Comment: 12 pages, Latex. Only selected Figures are included in 'jpg' format. Full resolution Figures as well as the "Maps" are available from the OGLE Internet archive: http://www.astrouw.edu.pl/~ogle or its US mirror http://bulge.princeton.edu/~ogl

The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. III. Period-Luminosity-Color and Period-Luminosity Relations of Classical Cepheids

We present Period-Luminosity-Color and Period-Luminosity relations of classical Cepheids constructed for about 1280 Cepheids from the LMC and 2140 from the SMC. High quality BVI observations (120-360 epochs in the I-band and 15-40 in the BV-bands) were collected during the OGLE-II microlensing experiment. The I-band diagrams of the LMC show very small scatter, \sigma=0.074 mag, indicating that Cepheid variables can potentially be a very good standard candle. We compare relations of fundamental mode Cepheids from the LMC and SMC and we do not find significant differences of slopes of the Period-Luminosity- Color and Period-Luminosity relations in these galaxies. For the first overtone Cepheids a small change of the slope of Period-Luminosity relation is possible. We determine the difference of distance moduli between the SMC and LMC with Cepheid relations and compare the result with difference obtained with other standard candles: RR Lyr and red clump stars. Results are very consistent and indicate that the values of zero points of the fundamental mode Cepheid relations are similar in these galaxies. The mean difference of distance moduli between the SMC and LMC is equal to \mu_SMC-\mu_LMC=0.51\pm0.03 mag. We calibrate the Period-Luminosity-Color and Period-Luminosity relations for classical, fundamental mode Cepheids using the observed LMC relations and adopting the short LMC distance modulus, \mu_LMC=18.22\pm0.05 mag, resulting from the recent determination with eclipsing system HV2274, RR Lyr and red clump stars and consistent with observations of Cepheids in NGC4258 galaxy, to which precise geometric distance is known. Finally, we determine a constraint on the absolute magnitude of Cepheids by comparison of their mean V-band magnitude with that of RR Lyr stars in both Magellanic Clouds.Comment: 24 pages, Latex+psfig. Acta Astronomica 49, 201. Revisions include: Larger by 3% sample of LMC Cepheids and therefore slightly different numbers in PL relations, discussion of Cepheids in NGC425

The Optical Gravitational Lensing Experiment. Catalog of Microlensing Events in the Galactic Bulge

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*10^9 photometric measurements of about 20.5 million stars from the Galactic bulge. The Catalog comprises 214 cases of 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.Comment: 25 pages, Latex+psfig. Only two pages of Appendix are included. Submitted to Acta Astronomica. Full Appendix, the entire Catalog and photmetric data are available from the OGLE Internet archive: http://www.astrouw.edu.pl/~ogle or its US mirror http://www.astro.princeton.edu/~ogle Minor changes, a few references adde

The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. V. Catalog of Cepheids from the Small Magellanic Cloud

We present the Catalog of Cepheids from the SMC which contains data for 2049 objects detected in the 2.4 square degree area of central parts of the SMC. For each object period, BVI photometry, astrometry, and R_21, \phi_21 parameters of the Fourier decomposition of I-band light curve are provided. The Catalog is based on observations collected during the OGLE-II microlensing survey. Tests of completeness performed in overlapping parts of adjacent fields indicate that completeness of the Catalog is very high: about 92%. Statistics and distributions of basic parameters of Cepheids are also presented. All presented data, including individual BVI observations (about 4.7*10^5 BVI measurements), are available from the OGLE Internet archive.Comment: 18 pages, Latex+psfig. Fig. 1 and Appendices (only one page) in JPG format. Submitted to Acta Astronomica. Full resolution Figure 1, all Appendices and the entire Catalog are available from the OGLE Internet archive: http://www.astrouw.edu.pl/~ogle or its US mirror http://www.astro.princeton.edu/~ogl