Results for "A. Udalski"

total 211175took 0.12s
The Optical Gravitational Lensing Experiment. Real Time Data Analysis Systems in the OGLE-III SurveyJan 08 2004We describe three real time data analysis systems implemented during the third phase of the OGLE survey (OGLE-III). The EWS system is designed to detect on-going microlensing events. The EEWS system monitors the microlensing phenomena for anomalies from ... More
The Optical Gravitational Lensing Experiment. Red Clump Stars as a Distance IndicatorOct 08 1999Jan 14 2000We present relation of the mean I-band brightness of red clump stars on metallicity. Red clump stars were proposed to be a very attractive standard candle for distance determination. The calibration is based on 284 nearby red giant stars whose high quality ... More
XROM and RCOM: Two New OGLE-III Real Time Data Analysis SystemsOct 13 2008We 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 ... More
The Optical Gravitational Lensing Experiment. Is Interstellar Extinction Toward the Galactic Center Anomalous?Oct 16 2002Mar 03 2003Photometry of the Galactic bulge, collected during the OGLE-II microlensing search, indicates high and non-uniform interstellar extinction toward the observed fields. We use the mean I-band magnitude and V-I color of red clump stars as a tracer of interstellar ... More
Optical Gravitational Lensing Experiment. Population Effects on the Mean Brightness of the Red Clump StarsJul 09 1998Sep 02 1998We present an empirical test indicating that the mean I-band magnitude of the red clump stars, used as the standard candle in the recent distance determinations to the Magellanic Clouds and other objects, is age independent for intermediate age (2-10 ... More
Identification of V735 Sgr as an Active Herbig Ae/Be ObjectOct 25 2018V735 Sgr was known as an enigmatic star with rapid brightness variations. Long-term OGLE photometry, brightness measurements in infrared bands, and recently obtained moderate resolution spectrum from the 6.5-m Magellan telescope show that this star is ... More
The Optical Gravitational Lensing Experiment. Stellar Distance Indicators in the Magellanic Clouds and Constraints on the Magellanic Cloud Distance ScaleOct 07 2000BVI photometry of the Magellanic Clouds collected during the OGLE-II microlensing experiment makes it possible to study in detail photometric properties of the "major" stellar distance indicators in the Magellanic Clouds. In addition to Cepheids, RR Lyr ... More
Optical Gravitational Lensing Experiment. The Distance Scale: Galactic Bulge - LMC - SMCMay 16 1998We analyze the mean luminosity of three samples of field RRab Lyr stars observed in the course of the OGLE microlensing experiment: 73 stars from the Galactic bulge and 110 and 128 stars from selected fields in the LMC and SMC, respectively. The fields ... More
The Light Curve Shapes as a Key to Resolving the Origin of Long Secondary Periods in Red Giant StarsApr 16 2014We present a study of OGLE light curves of red giant stars exhibiting long secondary periods (LSPs) - an enigmatic phenomenon commonly observed in stars on the upper red giant branch and asymptotic giant branch. We show that the light curves of LSP stars ... More
The Optical Gravitational Lensing Experiment. Population II Cepheids in the Galactic BulgeJun 26 2003We present I-band light curves of 54 Population II Cepheids identified in the OGLE-II catalog of variable objects in the Galactic bulge fields. Their periods range from a fraction of a day to several days. Their light curves show very close similarity ... More
The Optical Gravitational Lensing Experiment. Ages of about 600 Star Clusters from the LMCOct 18 2000We 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 ... More
The Optical Gravitational Lensing Experiment. Variable Stars in Star Clusters of the Magellanic Clouds. I. Eclipsing Systems in the Clusters of the SMCJun 22 1999The 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 ... More
The Optical Gravitational Lensing Experiment. Age of Star Clusters from the SMCJun 22 1999Jul 09 1999We 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 ... More
The Optical Gravitational Lensing Experiment. Cepheids in Star Clusters from the Magellanic CloudsDec 09 1999We 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, ... More
The Optical Gravitational Lensing Experiment. Multiple Cluster Candidates in the Large Magellanic CloudOct 16 2000We 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 ... More
The Optical Gravitational Lensing Experiment. Multiple Cluster Candidates in the Small Magellanic CloudJun 22 1999Jul 09 1999We 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 ... More
The Optical Gravitational Lensing Experiment. Investigating the Influence of Blending on the Cepheid Distance Scale with Cepheids in the Large Magellanic CloudSep 21 1999We investigate the influence of blending on the Cepheid distance scale. Blending leads to systematically low distances to galaxies observed with HST, and therefore to systematically high estimates of the Hubble constant H_0. We select a sample of 43 long-period, ... More
The influence of binarity on dust obscuration events in the planetary nebula M 2-29 and its analoguesJan 25 2011The central star of the planetary nebula (CSPN) M 2-29 shows an extraordinary R Coronae Borealis-like fading event in its optical lightcurve. The only other CSPN to show these events are CPD-568032 (Hen 3-1333) and V651 Mon (NGC 2346). Dust cloud formation ... More
Three-Dimensional Distributions of Type II Cepheids and Anomalous Cepheids in the Magellanic Clouds. Do these Stars Belong to the Old, Young or Intermediate-Age Population?Sep 05 2018Oct 24 2018The nature of type II Cepheids and anomalous Cepheids is still not well known and their evolutionary channels leave many unanswered questions. We use complete collection of classical pulsating stars in the Magellanic Clouds discovered by the OGLE project, ... More
Pulsation Modes of Long-Period Variables in the Period-Luminosity PlaneOct 28 2013We present a phenomenological analysis of long-period variables (LPVs) in the Large Magellanic Cloud with the aim of detecting pulsation modes associated to different period-luminosity (PL) relations. Among brighter LPVs we discover a group of triple-mode ... More
OGLE-IV: Fourth Phase of the Optical Gravitational Lensing ExperimentApr 22 2015We present both the technical overview and main science drivers of the fourth phase of the Optical Gravitational Lensing Experiment (hereafter OGLE-IV). OGLE-IV is currently one of the largest sky variability surveys worldwide, targeting the densest stellar ... More
Contact Binaries in OGLE-I DatabaseOct 13 2001Oct 16 2001We present a new catalog of 1575 contact binary stars fainter than I=18 mag identified in OGLE-I database in the selected directions toward the Galactic bulge and the Galactic bar. For completeness we recall here also the objects from the formerly published ... More
Optical Gravitational Lensing Experiment. OGLE-2 -- the Second Phase of the OGLE ProjectOct 09 1997We describe a new 1.3 m Warsaw telescope located at Las Campanas Observatory and new instruments of the second phase of the Optical Gravitational Lensing Experiment - OGLE-2. Results of first observations are also presented.
Photometric standard stars in the BVI system in a wide field centered on the spiral galaxy NGC 300Feb 20 2002Based on 13 nights of observations of four fields in NGC 300, we have set up an extensive sequence of stars with accurate BVI photometry covering a relatively large (25 x 25 arcmin) region centered on this galaxy. This sequence of standard stars is very ... More
OGLE-ing the Magellanic System: Photometric Metallicity from Fundamental Mode RR Lyrae StarsJul 29 2016In an era of extensive photometric observations, the catalogs of RR Lyrae type variable stars number tens of thousands of objects. The relation between the iron abundance [Fe/H] and the Fourier parameters of the stars light curve allows us to investigate ... More
Extracting Microlensing Signals from K2 Campaign 9Apr 27 2017Aug 20 2017The reduction of the \emph{K2}'s Campaign 9 (K2C9) microlensing data is challenging mostly because of the very crowded field and the unstable pointing of the spacecraft. In this work, we present the first method that can extract microlensing signals from ... More
Very Long-term Optical Variability of High Mass X-ray Binaries in the SMCDec 21 2010We have studied the very long-term temporal properties of the optical emission from Be X-ray binaries (BeX) in the Small Magellanic Cloud over a ~ 16 yr baseline, using light curves from the MACHO and OGLE databases. All the BeX in our sample display ... More
A remarkable sample of new symbiotic stars towards the Galactic BulgeMay 21 2013Symbiotic stars are the longest orbital period interacting binaries, where nova-like outbursts are generated by the accretion of a high mass loss rate red giant wind onto a white dwarf companion. Long-term photometric monitoring surveys such as OGLE and ... More
An Investigation of Be/X-ray Pulsars with OGLE-III DataMay 16 2006We have studied five seasons of OGLE-III data for eight SMC Be/X-ray pulsars for which no other survey data were available. We have determined orbital periods for four of these binary systems, one of which also shows nonradial pulsations. Optical identification ... More
A detailed study of the modulation of the optical light from Sk160/SMC X-1May 02 2013May 03 2013Eight years of optical photometry from OGLE-III are presented of the optical counterpart to the High Mass X-ray Binary system, SMC X-1. The optical data provide the best view to date of the modulation of the light from the system at the binary period ... More
The distance to the Galactic Centre based on Population-II Cepheids and RR Lyrae starsJan 17 2008Context: The distance to the Galactic Centre (GC) is of importance for the distance scale in the Universe. The value derived by Eisenhauer et al. (2005) of 7.62 +- 0.32 kpc based on the orbit of one star around the central black hole is shorter than most ... More
OGLE-III Detection of the Anomalous Galactic Bulge Red Giant Branch Bump: Evidence of Enhanced Helium EnrichmentNov 18 2010Feb 02 2011We measure the red giant branch bump (RGBB) of the Galactic bulge, the most metal-rich RGBB ever detected. The RGBB luminosity functions peaks at the expected brightness, but its number density is very low relative to Galactic globular cluster calibrations, ... More
Multi-wavelength properties of IGR J05007-7047 (LXP 38.55) and identification as a Be X-ray binary pulsar in the LMCJun 15 2016We report on the results of a $\sim$40 d multi-wavelength monitoring of the Be X-ray binary system IGR J05007-7047 (LXP 38.55). During that period the system was monitored in the X-rays using the Swift telescope and in the optical with multiple instruments. ... More
The Optical Gravitational Lensing Experiment. Final Reductions of the OGLE-III DataJul 24 2008We 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 ... More
Photometric analysis of Magellanic Cloud R Coronae Borealis Stars in the recovery phase of their declinesFeb 07 2009This paper presents the initial results of a multi-site photometric programme to examine the extraordinary behaviour displayed by 18 R Coronae Borealis (RCB) stars in the Magellanic Clouds (MCs). RCB stars exhibit a unique variability whereby they undergo ... More
Swift J0513.4-6547 = LXP 27.2 : a new Be/X-ray binary system in the Large Magellanic CloudDec 04 2014An exceptionally bright new X-ray source in the Large Magellanic Cloud was discovered by the Swift/BAT telescope on MJD 54923 (2 April 2009), and shown to have a pulse period of 27s using follow-up observations by RXTE/PCA. We report here on detailed ... More
$12\;660$ spotted stars toward the OGLE Galactic bulge fieldsMar 13 2019We present the discovery and statistical analysis of $12\;660$ spotted variable stars toward and inside the Galactic bulge from over two-decade-long Optical Gravitational Lensing Experiment (OGLE) data. We devise a new method of dereddening of individual ... More
RXJ0123.4-7321, a Be/X-ray binary in the wing of the SMCJan 15 2013To confirm faint Be/X-ray binary candidates from the XMM-Newton survey of the Small Magellanic Cloud, we searched for X-ray outbursts in archival ROSAT observations. We found that RXJ0123.4-7321 was much brighter when detected with ROSAT than seen 16 ... More
The Araucaria Project: Dependence of mean K, J, and I absolute magnitudes of red clump stars on metallicity and ageFeb 06 2003(Abridged) We present results of deep near-infrared JK imaging of LMC, SMC, and the Carina and Fornax dwarf galaxies. A comparison of the extinction-corrected K-band red clump star magnitudes with the tip of the red giant branch magnitude, the mean RR ... More
Type II Cepheids Pulsating in the First Overtone from the OGLE SurveyFeb 06 2019We report the discovery of the first type II Cepheids (BL Herculis stars) pulsating solely in the first overtone. We found two such objects among tens of millions of stars regularly observed by the OGLE survey in the Large Magellanic Cloud. Our classification ... More
Photometric Analysis of Variable Stars in NGC 299Feb 27 2013Apr 19 2013We have analyzed OGLE-III photometry for stars in the SMC cluster NGC 299. Two eclipsing binaries and one intrinsic variable (most likely a Be star) are identified. Unlike other young SMC clusters, no low-amplitude pulsating variables are present.
V5852 Sgr: An Unusual Nova Possibly Associated with the Sagittarius StreamJun 08 2016We report spectroscopic and photometric follow-up of the peculiar nova V5852~Sgr (discovered as OGLE-2015-NOVA-01), which exhibits a combination of features from different nova classes. The photometry shows a flat-topped light curve with quasi-periodic ... More
Binary Planetary Nebulae Nuclei towards the Galactic Bulge. I. Sample Discovery, Period Distribution and Binary FractionJan 28 2009Binarity has been hypothesised to play an important, if not ubiquitous, role in the formation of planetary nebulae (PNe). Yet there remains a severe paucity of known binary central stars required to test the binary hypothesis and to place strong constraints ... More
Discovery of Eclipsing Binary Central Stars in the Planetary Nebulae M 3-16, H 2-29 and M 2-19Aug 05 2008Progress in understanding the formation and evolution of planetary nebulae (PN) has been restricted by a paucity of well-determined central star masses. To address this deficiency we aim to (i) significantly increase the number of known eclipsing binary ... More
Optical and X-ray Properties of CAL 83: I. Quasi-periodic Optical and Supersoft VariabilityApr 15 2013We have studied the long-term (~ years) temporal variability of the prototype supersoft X-ray source (SSS) CAL 83 in the LMC, using data from the MACHO and OGLE projects. The CAL 83 light curve exhibits dramatic brightness changes of ~1 mag on timescales ... More
Multiwavelength observations of nova SMCN 2016-10a --- one of the brightest novae ever observedOct 10 2017We report on multiwavelength observations of nova SMCN 2016-10a. The present observational set is one of the most comprehensive for any nova in the Small Magellanic Cloud, including: low, medium, and high resolution optical spectroscopy and spectropolarimetry ... More
On the periodicities present in the optical light curves of SMC Be/X-ray binariesApr 24 2012We present a comprehensive study of the periodic variations observed in OGLE I-band light curves of SMC Be/X-ray binaries, discovering new optical periodicities in 9 systems. We find that these periodicities derive from a number of mechanisms, notably ... More
The Araucaria Project. Population effects on the V and I band magnitudes of red clump starsAug 06 2010We present measurements of the V and I band magnitudes of red clump stars in 15 nearby galaxies obtained from recently published homogenous HST photometry. Supplementing these results with similar data for another 8 galaxies available in the literature ... More
The Split Red Clump of the Galactic Bulge from OGLE-IIIJul 28 2010The red clump is found to be split into two components along several sightlines toward the Galactic Bulge. This split is detected with high significance toward the areas (-3.5<l<1,b<-5) and (l,b)=(0,+5.2), i.e., along the Bulge minor axis and at least ... More
Spectroscopic classification of X-ray sources in the Galactic Bulge SurveyMay 30 2017We present the classification of 26 optical counterparts to X-ray sources discovered in the Galactic Bulge Survey. We use (time-resolved) photometric and spectroscopic observations to classify the X-ray sources based on their multi-wavelength properties. ... More
Discovery of a 168.8 s X-ray pulsar transiting in front of its Be companion star in the Large Magellanic CloudFeb 19 2013Apr 15 2013We report the discovery of LXP169, a new high-mass X-ray binary (XRB) in the LMC. The optical counterpart has been identified and appears to exhibit an eclipsing light curve. We performed follow-up observations to clarify the eclipsing nature of the system. ... More
Curious Variables Experiment (CURVE). TT Bootis - superhump period change pattern confirmedAug 04 2004We report extensive multi-station photometry of TT Boo during its June 2004 superoutburst. The amplitude of the superoutburst was about 5.5 mag and its length over 22 days. The star showed a small re-brightening starting around the 9th day of the superoutburst. ... More
The Araucaria Project. Binary Classical Cepheids in the LMCJul 07 2014The status of our work on binary classical cepheid systems in the Large Magellanic Cloud is presented. We report on results from our follow up of two eclipsing binary cepheids OGLE-LMC-CEP-0227 and OGLE-LMC-CEP-1812. Here we presented for the first time ... More
SALT long-slit spectroscopy of LBQS 2113-4538: variability of the Mg II and Fe II componentAug 19 2013Jan 02 2014The Mg II line is of extreme importance in intermediate redshift quasars since it allows us to measure the black hole mass in these sources and to use these sources as probes of the distribution of dark energy in the Universe, as a complementary tool ... More
A first-overtone RR Lyrae star with cyclic period changesJul 20 2004A detailed light curve analysis is presented for a first-overtone RR Lyrae star, MACHO* J050918.712-695015.31, based on MACHO and OGLE-III observations. As a foreground object of the Large Magellanic Cloud, it gives an extraordinary opportunity to study ... More
A High-Resolution Spectrum of the Extremely Metal-Rich Bulge G-Dwarf OGLE-2006-BLG-265Aug 30 2006We present an R=45,000 Keck spectrum of the microlensed Galactic bulge G-dwarf OGLE-2006-BLG-265, which has a high (~60) signal-to-noise ratio despite its short (15 min) exposure time because the source was magnified by A~135. While it is very metal-rich ... More
The Optical Gravitational Lensing Experiment. Variable Stars in Globular Clusters - IV. Fields 104A-E in 47 TucMay 05 1997Five fields located close to the center of the globular cluster NGC 104=47 Tuc were surveyed in a search for variable stars. We present V-band light curves for 42 variables. This sample includes 13 RR Lyr stars -- 12 of them belong to the Small Magellanic ... More
The Optical Gravitational Lensing Experiment. Eclipsing Binaries and SX~Phe Stars in Omega~Cen and 47~TucJul 30 1995Extensive monitoring of the central part of Omega Cen has lead to the discovery of 12 eclipsing binaries and 9 SX~Phe stars. We report also finding 6 contact binaries in the field of 47~Tuc.
The Optical Gravitational Lensing Experiment. Follow-Up Observations of the Macho Microlensing Event in the Galactic BulgeNov 22 1994We present follow-up observations of a gravitational microlensing candidate found by the MACHO collaboration in the Galactic bulge. The photometric data cover a period near the maximum of the event and may be used to construct complete light curve. The ... More
The Optical Gravitational Lensing Experiment. Search for Planetary and Low-Luminosity Object Transits in the Galactic Disk. Results of 2001 Campaign - SupplementJul 05 2002The photometric data collected during 2001 season OGLE-III planetary/low luminosity object transit campaign were reanalyzed with the new transit search technique -- the BLS method by Kovacs, Zucker and Mazeh. In addition to all presented in our original ... More
The Optical Gravitational Lensing Experiment. Planetary and Low-Luminosity Object Transits in the Carina Fields of the Galactic DiskJan 13 2003We present results of the second planetary and low-luminosity object transit campaign conducted by the OGLE-III survey. Three fields (35'x35' each) located in the Carina regions of the Galactic disk (l~290) were monitored continuously in February-May ... More
Difference Image Analysis of the OGLE-II Bulge Data. III. Catalog of 200,000 Candidate Variable StarsJan 23 2002We 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 ... More
The Optical Gravitational Lensing Experiment. A Hunt for Caustic Crossings in QSO 2237+0305Apr 20 2000In 1998 The Optical Gravitational Lensing Experiment (OGLE) successfully implemented automated data reductions for QSO 2237+0305. Using a new image subtraction method we achieved a differential photometry scatter of 1-5 % for images A-D respectively. ... More
The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. II. Single-Mode Second Overtone Cepheids in the Small Magellanic CloudMar 25 1999Apr 06 1999We present a sample of 13 candidates for single-mode second overtone Cepheids discovered in the 2.4 square degree area of the SMC bar during the OGLE microlensing search. All candidates passed four photometric tests: analysis of Fourier parameters of ... More
The Optical Gravitational Lensing Experiment. UBVI Photometry of Stars in Baade's WindowAug 05 1999Sep 01 1999We present UBVI photometry for 8530 stars in Baade's Window obtained during the OGLE-II microlensing survey. Among these are over one thousand red clump giants. 1391 of them have photometry with errors smaller than 0.04, 0.06, 0.12, and 0.20 mag in the ... More
The Optical Gravitational Lensing Experiment. Eclipsing Binary Stars in the Small Magellanic CloudDec 18 1998We 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 ... More
The Optical Gravitational Lensing Experiment. BVI Maps of Dense Stellar Regions. I. The Small Magellanic CloudJun 23 1998Jul 01 1998We 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 ... More
The Optical Gravitational Lensing Experiment. Catalog of Star Clusters from the Large Magellanic CloudDec 09 1999We 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, ... More
The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. III. Period-Luminosity-Color and Period-Luminosity Relations of Classical CepheidsJul 17 1999Sep 02 1999We 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 ... More
The Optical Gravitational Lensing Experiment. Photometry of the MACHO-SMC-98-1 Binary Microlensing EventAug 08 1998Sep 02 1998We 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 ... More
Optical Gravitational Lensing Experiment. Distance to the Magellanic Clouds with the Red Clump Stars: Are the Magellanic Clouds 15% Closer than Generally Accepted?Mar 04 1998Mar 13 1998We 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 ... More
Modelling the Galactic Bar Using Red Clump GiantsMay 27 1996The color-magnitude diagrams of $\sim 7 \times 10^5$ stars obtained for 12 fields across the Galactic bulge with the OGLE project reveal a well-defined population of bulge red clump giants. We find that the distributions of the apparent magnitudes of ... More
The Optical Gravitational Lensing Experiment. The General Catalog of Stars in the Galactic Bulge. I. The Stars in the Central Baade's Window OGLE Field BWCApr 16 1996This paper presents the first part of the Optical Gravitational Lensing Experiment (OGLE) General Catalog of Stars in the Galactic bulge. The Catalog is based on observations collected during the OGLE microlensing search. This part contains 33196 stars ... More
The Optical Gravitational Lensing Experiment. Variable Stars in Globular Clusters -I. Fields 5139A-C in Omega CentauriJan 11 1996Three fields covering the central part of the globular cluster Omega Cen were surveyed in a search for variable stars. We present V-band light curves for 22 periodic variables: 9 SX~Phe stars, 7 contact binaries, 5 detached or semi-detached binaries, ... More
THE OPTICAL GRAVITATIONAL LENSING EXPERIMENT. THE CATALOG OF PERIODIC VARIABLE STARS IN THE GALACTIC BULGE. I. PERIODIC VARIABLES IN THE CENTER OF THE BAADE'S WINDOW.Jan 09 1995This paper is the first part of the Catalog of Periodic Variable Stars in the Galactic bulge. The Catalog is based on observations collected during the OGLE microlensing search. 213 periodic variable stars brighter than I=18 mag: 31 pulsating, 116 eclipsing ... More
A Second Method to Photometrically Align Multi-Site Microlensing Light Curves: Source Color in Planetary Event MOA-2007-BLG-192Oct 12 2009At present, microlensing light curves from different telescopes and filters are photometrically aligned by fitting them to a common model. We present a second method based on photometry of common field stars. If two spectral responses are similar (or ... More
The first confirmed microlens in a globular clusterDec 02 2011Dec 16 2011In 2000 July/August a microlensing event occurred at a distance of 2.33 arcmin from the center of the globular cluster M22 (NGC6656), observed against the dense stellar field of the Milky Way bulge. We have used the adaptive optics system NACO at the ... More
Modelling the Galactic Bar Using Red Clump StarsAug 01 1995The color-magnitude diagrams of $\sim 1 \times 10^6$ stars obtained for 19 fields towards the Galactic bulge with the OGLE project reveal a well-defined population of bulge red clump stars. We found that the distributions of the extinction-adjusted apparent ... More
The Optical Gravitational Lensing Experiment. the Early Warning SystemAug 08 1994The discoveries of 17 microlensing event candidates have been reported over the last year by three teams conducting unprecedented mass photometric searches in the direction of the Galactic bulge and the Magellanic Clouds. These include 10 events found ... More
Color-Magnitude Diagram Distribution of the Bulge Red Clump Stars - Evidence for the Galactic BarApr 15 1994The color-magnitude diagrams of $\sim 5\times 10^5$ stars obtained for 13 fields towards the Galactic bulge with the OGLE project reveal a well-defined population of bulge red clump stars. We find that the distributions of the extinction-adjusted apparent ... More
THE OPTICAL GRAVITATIONAL LENSING EXPERIMENT. THE CATALOG OF PERIODIC VARIABLE STARS IN THE GALACTIC BULGE. II. PERIODIC VARIABLES IN FOUR BAADE'S WINDOW FIELDS: BW1, BW2, BW3 AND BW4Apr 23 1995We present the second part of the OGLE Catalog of Periodic Variable Stars in the Galactic bulge. 800 variable stars found in four Baade's Window fields BW1, BW2, BW3 and BW4 are presented. Among them 71 are classified as pulsating, 465 as eclipsing and ... More
Clues to the Metallicity Distribution in the Galactic Bulge: Abundances in OGLE-2007_BLG-349SJan 21 2008Apr 08 2008We present an abundance analysis based on high dispersion and high signal-to-noise ratio Keck spectra of a very highly microlensed Galactic bulge dwarf, OGLE-2007-BLG-349S, with Teff ~ 5400 K. The amplification at the time the spectra were taken ranged ... More
The Optical Gravitational Lensing Experiment. Additional Planetary and Low-Luminosity Object Transits from the OGLE 2001 and 2002 Observational CampaignsJun 23 2003Jun 29 2003The photometric data collected by OGLE-III during the 2001 and 2002 observational campaigns aiming at detection of planetary or low-luminosity object transits were corrected for small scale systematic effects using the data pipeline by Kruszewski and ... More
Combined Analysis of the Binary-Lens Caustic-Crossing Event MACHO 98-SMC-1Jul 19 1999We fit the data for the binary-lens microlensing event MACHO 98-SMC-1 from 5 different microlensing collaborations and find two distinct solutions characterized by binary separation d and mass ratio q: (d,q)=(0.54,0.50) and (d,q)=(3.65,0.36), where d ... More
Difference Image Analysis of the OGLE-II bulge data. II. Microlensing eventsJun 26 2001We present a sample of microlensing events discovered in the Difference Image Analysis (DIA) of the OGLE-II images collected during 3 observing seasons, 1997--1999. 4424 light curves pass our criteria on the presence of a brightening episode on top of ... More
The Optical Gravitational Lensing Experiment. BVI Maps of Dense Stellar Regions. II. The Large Magellanic CloudOct 07 2000We 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. ... More
The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. V. Catalog of Cepheids from the Small Magellanic CloudDec 06 1999We 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 ... More
The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. IV. Catalog of Cepheids from the Large Magellanic CloudAug 29 1999Oct 13 1999We 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. ... More
The Optical Gravitational Lensing Experiment. Monitoring of QSO 2237+0305Apr 23 1999Apr 26 1999We present results from 2 years of monitoring of Huchra's lens (QSO 2237+0305) with the 1.3 m Warsaw telescope on Las Campanas, Chile. Photometry in the V band was done using a newly developed method for image subtraction. Reliable subtraction without ... More
A Search for Stellar-Mass Black Holes via Astrometric MicrolensingJul 27 2016While dozens of stellar mass black holes have been discovered in binary systems, isolated black holes have eluded detection. Their presence can be inferred when they lens light from a background star. We attempt to detect the astrometric lensing signatures ... More
The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. VI. Double-Mode Cepheids in the Large Magellanic CloudJan 19 2001We present a sample of 76 double-mode Cepheids detected in the 4.5 square degree area in the central part of the LMC. 19 stars from the sample pulsate in the fundamental mode and the first overtone while 57 objects are the first and second overtone pulsators. ... More
The Optical Gravitational Lensing Experiment. Catalog of Microlensing Events in the Galactic BulgeFeb 22 2000Mar 02 2000We 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 ... More
Optical Gravitational Lensing Experiment. Photometry of the MACHO-SMC-1 Microlensing CandidateOct 31 1997We 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 ... More
Evidence for the Galactic Bar from the Two Color Photometry of the Bulge Red Clump StarsOct 14 1994The Optical Gravitational Lensing Experiment (OGLE, Udalski et al.~1994a; Paczy\'nski et al.~1994b -- these proceedings; and references therein) is an extensive photometric search for the rare cases of gravitational microlensing of Galactic bulge stars ... More
A Low-Resolution Spectroscopic Exploration of Puzzling OGLE Variable StarsMar 11 2015Apr 29 2015We present the results of a spectroscopic follow-up of various puzzling variable objects detected in the OGLE-III Galactic disk and bulge fields. The sample includes mainly short-period multi-mode pulsating stars that could not have been unambiguously ... More
The Optical Gravitational Lensing Experiment. Small Amplitude Variable Red Giants in the Magellanic CloudsJul 02 2004We present analysis of the large sample of variable red giants from the Large and Small Magellanic Clouds detected during the second phase of the Optical Gravitational Lensing Experiment (OGLE-II) and supplemented with OGLE-III photometry. Comparing pulsation ... More
Chemical Composition of Faint (I~21 mag) Microlensed Bulge Dwarf OGLE-2007-BLG-514SOct 07 2009We present a high-resolution spectrum of a microlensed G dwarf in the Galactic bulge with spectroscopic temperature T_eff = 5600 +/- 180 K. This I~21 mag star was magnified by a factor ranging from 1160 to 1300 at the time of observation. Its high metallicity ... More
The Optical Gravitational Lensing Experiment. Cepheids in the Galaxy IC1613: No Dependence of the Period--Luminosity Relation on MetallicitySep 25 2001We present results of the search for Cepheids in the galaxy IC1613 carried out as a sub-project of the OGLE-II microlensing survey. 138 Cepheids were found in the 14.2x14.2 arcmin region in the center of the galaxy. We present light curves, VI photometry ... More
The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. I. Double-Mode Cepheids in the Small Magellanic CloudMar 25 1999Apr 07 1999We present a sample of 93 double-mode Cepheids detected in the 2.4 square degree area in the central part of the SMC. 23 stars from the sample pulsate in the fundamental mode and the first overtone while 70 objects are the first and second overtone pulsators. ... More
The Optical Gravitational Lensing Experiment. Short Distance Scale to the LMCSep 27 1998Oct 21 1998We present {\it UBVI} photometry of the eclipsing binary HV2274 - the system which has been recently used for distance determination to the LMC by Guinan et al. (1998). We determine the interstellar reddening to the star, E(B-V)=0.149+/-0.015 mag, based ... More