6,049 research outputs found
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
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