- ID:
- ivo://CDS.VizieR/J/AcA/51/221
- Title:
- OGLE-II. Cepheids in IC 1613
- Short Name:
- J/AcA/51/221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of the search for Cepheids in the galaxy IC 1613 carried out as a sub-project of the OGLE-II microlensing survey. 138 Cepheids were found in the 14.2'x14.2' region in the center of the galaxy. We present light curves, VI photometry and basic data for all these objects, as well as color-magnitude diagram of the observed field.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AcA/50/421
- Title:
- OGLE-II DIA BUL_SC1 field
- Short Name:
- J/AcA/50/421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an implementation of the difference image photometry based on the Alard and Lupton optimal PSF matching algorithm. The most important feature distinguishing this method from the ones using Fourier divisions is that equations are solved in real space and the knowledge of each PSF is not required for determination of the convolution kernel. We evaluate the method and software on 380G B of OGLE-II bulge microlensing data obtained in 1997-1999 observing seasons. The error distribution is Gaussian to better than 99% with the amplitude only 17% above the photon noise limit for faint stars. Over the entire range of the observed magnitudes the resulting scatter is improved by a factor of 2-3 compared to DoPhot photometry, currently a standard tool for massive stellar photometry in microlensing searches. For testing purposes the photometry of approx 4600 candidate variable stars and sample difference image data are provided for BUL_SC1 field. In the candidate selection process, very few assumptions have been made about the specific types of flux variations, which makes this data set well suited for general variability studies, including the development of the classification schemes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/385/905
- Title:
- OGLEII high pm stars towards Galactic Centre
- Short Name:
- J/MNRAS/385/905
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The photometry data base of the second phase of the OGLE microlensing experiment, OGLE-II, is a rich source of information about the kinematics and structure of the Galaxy. In this work, we use the OGLE-II proper motion catalogue to identify candidate stars which have high proper motions. 521 stars with proper motion {mu}>50mas/yr in the OGLE-II proper motion catalogue were cross-identified with stars in the MACHO high proper motion catalogue, and the DEep Near-Infrared Survey and Two-Micron All-Sky Survey infrared photometry catalogues. Photometric distances were computed for stars with colours consistent with G/K- and M-type stars. Six stars were newly identified as possible nearby (<50pc) M dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/61
- Title:
- OGLE-III, MCPS and HST VI obs. of LMC & SMC
- Short Name:
- J/ApJ/886/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a calibration of the tip of the red giant branch (TRGB) in the Large Magellanic Cloud (LMC) on the Hubble Space Telescope (HST)/ACS F814W system. We use archival HST observations to derive blending corrections and photometric transformations for two ground-based wide-area imaging surveys of the Magellanic Clouds. We show that these surveys are biased bright by up to ~0.1mag in the optical due to blending, and that the bias is a function of local stellar density. We correct the LMC TRGB magnitudes from Jang & Lee (2017ApJ...835...28J) and use the geometric distance from Pietrzynski+ (2019Natur.567..200P) to obtain an absolute TRGB magnitude of M_F814W_=-3.97+/-0.046mag. Applying this calibration to the TRGB magnitudes from Freedman+ (2019ApJ...882...34F) in SN Ia hosts yields a value for the Hubble constant of H_0_=72.4+/-2.0km/s/Mpc for their TRGB+SNe Ia distance ladder. The difference in the TRGB calibration and the value of H_0_ derived here and by Freedman+ primarily results from their overestimate of the LMC extinction, caused by inconsistencies in their different sources of TRGB photometry for the Magellanic Clouds. Using the same source of photometry (OGLE) for both Clouds and applying the aforementioned corrections yields a value for the LMC I-band TRGB extinction that is lower by 0.06mag, consistent with independent OGLE reddening maps used by us and by Jang & Lee to calibrate TRGB and determine H0.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/20
- Title:
- OGLE-III Mira variables in the Magellanic Clouds
- Short Name:
- J/ApJ/884/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Period-Luminosity and Period-Luminosity-Color relations at maximum light for Mira variables in the Magellanic Clouds using time-series data from the Optical Gravitational Lensing Experiment (OGLE-III) and Gaia data release 2. The maximum-light relations exhibit a scatter typically up to ~30% smaller than their mean-light counterparts. The apparent magnitudes of oxygen-rich Miras at maximum light display significantly smaller cycle-to-cycle variations than at minimum light. High-precision photometric data for Kepler Mira candidates also exhibit stable magnitude variations at the brightest epochs, while their multi-epoch spectra display strong Balmer emission lines and weak molecular absorption at maximum light. The stability of maximum-light magnitudes for Miras possibly occurs due to the decrease in the sensitivity to molecular bands at their warmest phase. At near-infrared wavelengths, the period-luminosity relations (PLRs) of Miras display similar dispersion at mean and maximum light with limited time-series data in the Magellanic Clouds. A kink in the oxygen-rich Mira PLRs is found at 300 days in the VI-bands, which shifts to longer periods (~350 days) at near-infrared wavelengths. Oxygen-rich Mira PLRs at maximum light provide a relative distance modulus, {Delta}{mu}=0.48+/-0.08mag, between the Magellanic Clouds with a smaller statistical uncertainty than the mean-light relations. The maximum-light properties of Miras can be very useful for stellar atmosphere modeling and distance scale studies provided their stability and the universality can be established in other stellar environments in the era of extremely large telescopes.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A20
- Title:
- OGLE-III parallax events with Gaia DR2
- Short Name:
- J/A+A/636/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context. Gravitational microlensing is sensitive to compact-object lenses in the Milky Way, including white dwarfs, neutron stars, or black holes, and could potentially probe a wide range of stellar-remnant masses. However, the mass of the lens can be determined only in very limited cases, due to missing information on both source and lens distances and their proper motions. Aims. Our aim is to improve the mass estimates in the annual parallax microlensing events found in the eight years of OGLE-III observations towards the Galactic Bulge with the use of Gaia Data Release 2 (DR2). Methods. We use Gaia DR2 data on distances and proper motions of non-blended sources and recompute the masses of lenses in parallax events. We also identify new events in that sample which are likely to have dark lenses; the total number of such events is now 18. Results. The derived distribution of masses of dark lenses is consistent with a continuous distribution of stellar-remnant masses. A mass gap between neutron star and black hole masses in the range between 2 and 5 solar masses is not favoured by our data, unless black holes receive natal kicks above 20-80km/s. We present eight candidates for objects with masses within the putative mass gap, including a spectacular multi-peak parallax event with mass of 2.4_-1.3_^+1.9^M_{sun}_ located just at 600pc. The absence of an observational mass gap between neutron stars and black holes, or conversely the evidence of black hole natal kicks if a mass gap is assumed, can inform future supernova modelling efforts.
- ID:
- ivo://CDS.VizieR/J/AcA/63/323
- Title:
- OGLE-III SMC eclipsing binary stars
- Short Name:
- J/AcA/63/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a large sample of eclipsing binary stars detected in the Small Magellanic Cloud fields covering about 14 square degrees that have been monitored for eight years during the third phase of the OGLE survey. This is the largest set of such variables containing 6138 objects, of which 777 are contact and 5361 non-contact binaries. The estimated completeness of this sample is around 82%. We analyze the statistical properties of the sample and present selected interesting objects: 32 systems having eccentric orbit with visible apsidal motion, one Transient Eclipsing Binary, ten RS CVn type stars, 22 still unexplained Double-Periodic Variable stars, and 15 candidates for doubly eclipsing quadruple systems. Based on the OGLE-III proper motions, we classified 47 binaries from our sample as foreground Galactic stars. We also list candidates suitable for the SMC distance determination.
- ID:
- ivo://CDS.VizieR/J/AcA/63/379
- Title:
- OGLE-III variable stars in Galactic disk area
- Short Name:
- J/AcA/63/379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for pulsating stars in the 7.12deg^2^ OGLE-III Galactic disk area in the direction tangent to the Centaurus Arm. We report the identification of 20 Classical Cepheids, 45 RR Lyr type stars, 31 Long-Period Variables, such as Miras and Semi-Regular Variables, one pulsating white dwarf, and 58 very likely {delta} Sct type stars. Based on asteroseismic models constructed for one quadruple-mode and six triple-mode {delta} Sct type pulsators, we estimated masses, metallicities, ages, and distance moduli to these objects. The modeled stars have masses in the range 0.9-2.5M_{sun}_ and are located at distances between 2.5kpc and 6.2kpc. Two triple-mode and one double-mode pulsators seem to be Population II stars of the SX Phe type, probably from the Galactic halo. Our sample also includes candidates for Type II Cepheids and unclassified short-period (P<0.23d) multi-mode stars which could be either {delta}Sct or {beta}Cep type stars. One of the detected variables is a very likely {delta} Sct star with an exceptionally high peak-to-peak I-band amplitude of 0.35mag at the very short period of 0.0196d. All reported pulsating variable stars but one object are new discoveries. They are included in the OGLE-III Catalog of Variable Stars. Finally, we introduce the on-going OGLE-IV Galactic Disk Survey, which covers more than half of the Galactic plane. For the purposes of future works on the spiral structure and star formation history of the Milky Way, we have already compiled a list of known Galactic Classical Cepheids.
- ID:
- ivo://CDS.VizieR/J/ApJ/636/240
- Title:
- OGLE II microlensing parameters
- Short Name:
- J/ApJ/636/240
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a measurement of the microlensing optical depth toward the Galactic bulge based on 4 years of the OGLE-II survey. We consider only bright sources in the extended red clump giant (RCG) region of the color-magnitude diagram, in 20 bulge fields covering ~5deg^2^ between 0{deg}<l<3{deg} and -4{deg}<b<-2{deg}. Using a sample of 32 events we find {tau}=2.55x10^-6^ at (l,b)=(1.16{deg},-2.75{deg}).
- ID:
- ivo://CDS.VizieR/J/AcA/54/1
- Title:
- OGLE II SMC eclipsing binaries
- Short Name:
- J/AcA/54/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new version of the OGLE-II catalog of eclipsing binary stars detected in the Small Magellanic Cloud, based on Difference Image Analysis catalog of variable stars in the Magellanic Clouds containing data collected from 1997 to 2000. We found 1351 eclipsing binary stars in the central 2.4 square degree area of the SMC. 455 stars are newly discovered objects, not found in the previous release of the catalog. The eclipsing objects were selected with the automatic search algorithm based on the artificial neural network. The full catalog with individual photometry is accessible from the OGLE INTERNET archive, at ftp://sirius.astrouw.edu.pl/ogle/ogle2/var_stars/smc/ecl . Regular observations of the SMC fields started on June 26, 1997 and covered about 2.4 square degrees of central parts of the SMC. Reductions of the photometric data collected up to the end of May 2000 were performed with the Difference Image Analysis (DIA) package.
