583 research outputs found
A ground-based proper motion study of twelve nearby Globular Clusters
We derive relative proper motions of stars in the fields of the globular
clusters M12, NGC 6362, M4, M55, M22, NGC 6752, NGC 3201, M30, M10, NGC 362,
M5, and 47 Tucanae based on data collected between 1997 and 2015 with the 1-m
Swope telescope of Las Campanas Observatory. We determine membership class and
membership probability for over 446 000 objects, and show that these are
efficient methods for separating field stars from members of the cluster. In
particular, membership probabilities of variable stars and blue/yellow/red
stragglers are determined. Finally, we find absolute proper motions for six
globular clusters from our sample: M55, NGC 3201, M10, NGC 362, M5, and 47 Tuc.
An electronic catalogue of the derived proper motions is publicly available via
the internet.Comment: 24 pages, 35 figures, 6 tables. Accepted for publication in MNRAS.
Figures of high quality on reques
The Optical Gravitational Lensing Experiment. OGLE-III Photometric Maps of the Galactic Bulge Fields
We present OGLE-III Photometric Maps of the Galactic bulge fields observed
during the third phase of the OGLE project. This paper describes the last,
concluding set of maps based on OGLE-III data.
The maps contain precise, calibrated VI photometry of about 340 million stars
from 267 fields in the Galactic bulge observed during entire OGLE-III phase
(2002-2009), covering about 92 square degrees in the sky. Precise astrometry of
these objects is also provided.
We briefly discuss the photometry procedures and the quality of the data. We
also present sample data and color-magnitude diagrams of the observed fields.
All photometric data are available to the astronomical community from the
OGLE Internet archive.Comment: 15 pages, 12 figure
The Cluster AgeS Experiment (CASE). Variable stars in the field of the globular cluster M22
The field of the globular cluster M22 (NGC 6656) was monitored between 2000
and 2008 in a search for variable stars. light curves were obtained for
359 periodic, likely periodic, and long-term variables, 238 of which are new
detections. Thirty nine newly detected variables, and 63 previously known ones
are members or likely members of the cluster, including 20 SX Phe, 10 RRab and
16 RRc-type pulsators, one BL Her-type pulsator, 21 contact binaries, and 9
detached or semi-detached eclipsing binaries. The most interesting among the
identified objects are V112 - a bright multimode SX Phe pulsator, V125 - a
Lyr-type binary on the blue horizontal branch, V129 - a blue/yellow
straggler with a W UMa-like light curve, located halfway between the extreme
horizontal branch and red giant branch, and V134 - an extreme horizontal branch
object with d and a nearly sinusoidal light curve; all four of them
are proper motion (PM) members of the cluster. Among nonmembers, a d
detached eclipsing binary hosting a Sct-type pulsator was found, and a
peculiar d binary with ellipsoidal modulation and narrow minimum in
the middle of one of the descending shoulders of the sinusoid. We also
collected substantial new data for previously known variables; in particular we
revise the statistics of the occurrence of the Blazhko effect in RR Lyr-type
variables of M22.Comment: 21 pages, 8 figures, 3 table
The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. X. Enigmatic Class of Double Periodic Variables in the Large Magellanic Cloud
The tenth part of the OGLE-III Catalog of Variable Stars contains 125 Double
Periodic Variables (DPVs) from the Large Magellanic Cloud. DPVs are
semi-detached binaries which show additional variability with a period around
33 times longer than the orbital period. The cause of this long cycle is not
known and previous studies suggest it involves circumbinary matter. We discuss
the properties of the whole sample of the LMC DPVs and put more attention to
particularly interesting objects which may be crucial for verifying hypothesis
explaining long cycle variability. Secondary eclipses of one of the objects
disappear during some orbital cycles and primary eclipses are deeper during
long cycle minimum.Comment: 18 pages, 11 figure
The Optical Gravitational Lensing Experiment. The Catalog of Stellar Proper Motions toward the Magellanic Clouds
We present a catalog of over 6.2 million stars with measured proper motions.
All these stars are observed in the direction of the Magellanic Clouds within
the brightness range 12 < I < 19 mag. Based on these proper motions about 440
000 Galactic foreground stars can be selected. Because the proper motions are
based on a few hundred epochs collected during eight years, their statistical
uncertainties are below 0.5 mas/yr for stars brighter than I = 18.5 mag. The
parallaxes are derived with uncertainties down to 1.6 mas. For above 13 000
objects parallaxes are derived with significance above 3\sigma, which allows
selecting around 270 white dwarfs (WDs). The search for common proper motion
binaries among stars presented was performed resulting in over 500 candidate
systems. The most interesting ones are candidate halo main sequence star-WD and
WD-WD systems. The application of the catalog to empirically bound the Cepheid
instability strip is also discussed
The Optical Gravitational Lensing Experiment. High Proper Motion Stars in the OGLE-III Data for Magellanic Clouds Fields
We present the results of a search for High Proper Motion (HPM) stars, i.e.
the ones with \mu > 100 mas/yr, in the direction to the Magellanic Clouds. This
sky area was not examined in detail as the high stellar density hampers efforts
in performing high-quality astrometry.
Altogether 549 HPM stars were found with median uncertainties of proper
motions per coordinate equal to 0.5 mas/yr. The fastest HPM star has the proper
motion of 722.19 +/- 0.74 mas/yr. For the majority of objects (70%) parallaxes
were also measured. The highest value found is \pi = 91.3 +/-1.6 mas. The
parallaxes were used to estimate absolute magnitudes which enriched with color
information show that 21 of HPM stars are white dwarfs. Other 23 candidate
white dwarfs were selected of HPM stars with no measurable parallaxes using
color-magnitude diagram. The search for common proper motion binaries revealed
27 such pairs in the catalog. The completeness of the catalog is estimated to
be > 80% and it is slightly higher than for previous catalogs in the direction
to the Magellanic Clouds
The Optical Gravitational Lensing Experiment. Triple-Mode and 1O/3O Double-Mode Cepheids in the Large Magellanic Cloud
We report the discovery of three new triple-mode classical Cepheids in the
Large Magellanic Cloud, two of them with the fundamental, first overtone and
second overtone excited, and one pulsating simultaneously in the first three
overtones. Thus, the number of triple-mode Cepheids in the LMC is increased to
five. We also present two objects belonging probably to a new type of
double-mode Cepheids having the first and third overtones excited. We measure
the rates of period change in these stars and detect decrease of periods in two
of them, what is in conflict with theoretical predictions.Comment: 10 pages, 5 figure
The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. VI. Delta Scuti Stars in the Large Magellanic Cloud
The sixth part of the OGLE-III catalog of Variable Stars presents \delta Sct
pulsators in the Large Magellanic Cloud. Altogether 2786 variable stars were
found and amongst them 92 are multi-mode objects, including 67 stars pulsating
in the fundamental mode and the first overtone (F/1O), nine double-mode
pulsators with various combinations of the first three overtones excited
(1O/2O, 2O/3O and 1O/3O pulsators), and two triple mode (F/1O/2O) \delta Sct
stars. In total 1490 of stars are marked as uncertain, due to scattered
photometry and small amplitudes. For single-mode objects it was not possible to
unambiguously identify pulsation mode, however we suggest the most of the
single-mode variable stars pulsate in the first overtone.Comment: 16 pages, 7 figure
The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. XII. Eclipsing Binary Stars in the Large Magellanic Cloud
We present catalog of 26 121 visually inspected eclipsing binary stars
identified in the Large Magellanic Cloud during the third phase of the Optical
Gravitational Lensing Experiment. The sample is limited to the out-of-eclipse
brightness I < 20 mag. The catalog consists mostly of detached eclipsing
binaries - ellipsoidal variables were not included. For stars brighter than I =
18 mag the detection rate of eclipsing binaries is 0.5% and for all stars it
falls to 0.2%. The absolute completeness of the whole catalog is about 15%
assuming the occurence rate of EBs toward the LMC equal to 1.5%. Among
thousands of regular eclipsing systems we distinguished a subclass of eclipsing
binaries - transient eclipsing binaries (TEB) - presenting cycles of appearance
and disappearance of eclipses due to the precession of their orbits.Comment: published in Acta Astronomic
The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. V. R Coronae Borealis Stars in the Large Magellanic Cloud
The fifth part of the OGLE-III Catalog of Variable Stars presents 23 R CrB
(RCB) stars in the Large Magellanic Cloud (LMC). 17 of these objects have been
spectroscopically confirmed by previous studies, while 6 stars are new
candidates for RCB variables. We publish the VI multi-epoch OGLE photometry for
all objects.
We use the sample of carbon-rich long-period variables released in the
previous part of this catalog to select objects with severe drops in
luminosity, i.e. with the DY-Per-like light curves. DY Per stars are often
related to R CrB variables. We detect at least 600 candidates for DY Per stars,
mostly among dust enshrouded giants. We notice that our candidate DY Per stars
form a continuity with other carbon-rich long-period variables, so it seems
that DY Per stars do not constitute a separate group of variable stars.Comment: 13 pages, 5 color figure
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