- ID:
- ivo://CDS.VizieR/J/MNRAS/327/601
- Title:
- OGLE-II High proper motion stars
- Short Name:
- J/MNRAS/327/601
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The difference image analysis (DIA) of the images obtained by the Optical Gravitational Lensing Experiment (OGLE-II) revealed a peculiar artefact in the sample of stars proposed as variable by Woniak in one of the Galactic bulge fields: the occurrence of pairs of candidate variables showing anti-correlated light curves monotonic over a period of 3 yr. This effect can be understood, quantified and related to the stellar proper motions. DIA photometry supplemented with a simple model offers an effective and easy way to detect high proper motion stars in very dense stellar fields, where conventional astrometric searches are extremely inefficient.
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- 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/562/A125
- Title:
- OGLE-III SMC massive stars VI light curves
- Short Name:
- J/A+A/562/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a variability study of 4646 massive stars in the Small Magellanic Cloud (SMC) with known spectral types from the catalog of Bonanos et al. (2010, Cat. J/AJ/140/416) using the light curves from the OGLE-III database. The goal is to exploit the time domain information available through OGLE-III to gain insight into the processes that govern the evolution of massive stars. This variability survey of massive stars with known spectral types is larger than any previous survey by a factor of 7. We find that 60% of our sample (2766 stars) show no significant variability and 40% (1880 stars) exhibit variability distributed as follows: 807 stars display low-amplitude stochastic variability with fluctuations in I-band of up to 0.05mag, 443 stars present irregular variability of higher amplitude (76% of these are reported as variables for the first time), 205 are eclipsing binaries (including 101 newly discovered systems), 50 are candidate rotating variables, 126 are classical Cepheids, 188 stars exhibit short-term sinusoidal periodicity (P<3-days) making them candidate 'slowly pulsating B stars' and non-radial Be pulsators, and 61 periodic stars exhibit longer periods. We demonstrate the wealth of information provided in the time domain, by doubling the number of known massive eclipsing binary systems and identifying 189 new candidate early-type Be and 20 Oe stars in the SMC. In addition, we find that ~80% of Be stars are photometrically variable in the OGLE-III time domain and provide evidence that short-term pulsating stars with additional photometric variability are rotating close to their break-up velocity.
- 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/48/289
- Title:
- OGLE-I long-period and non-periodic variables
- Short Name:
- J/AcA/48/289
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a list of long-period and non-periodic variable stars detected in the OGLE-I database. These stars were not included in previous catalogs of periodic stars found in OGLE data. The catalog contains 116 stars in twelve Baade's Window fields and additionally in the Galactic bulge fields: MM1/5/7-A/B, MM3 and GB1.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A123
- Title:
- OGLE IV and Gaia EDR3 data for RR Lyrae stars
- Short Name:
- J/A+A/657/A123
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- RR Lyrae stars are useful standard candles allowing one to derive accurate distances for old star clusters. Based on the recent catalogues from OGLE-IV and Gaia Early Data Release 3 (EDR3), the distances can be improved for a few bulge globular clusters. The aim of this work is to derive an accurate distance for the following six moderately metal-poor, relatively high-reddening bulge globular clusters: NGC 6266, NGC 6441, NGC 6626, NGC 6638, NGC 6642, and NGC 6717. We combined newly available OGLE-IV catalogues of variable stars containing mean I magnitudes, with Clement's previous catalogues containing mean V magnitudes, and with precise proper motions from Gaia EDR3. Astrometric membership probabilities were computed for each RR Lyrae, in order to select those compatible with the cluster proper motions. Applying luminosity-metallicity relations derived from BaSTI alpha-enhanced models (He-enhanced for NGC 6441 and canonical He for the other clusters), we updated the distances with relatively low uncertainties. Distances were derived with the I and V bands, with a 5-8% precision. We obtained 6.6kpc, 13.1kpc, 5.6 kpc, 9.6kpc, 8.2kpc, and 7.3kpc for NGC 6266, NGC 6441, NGC 6626, NGC 6638, NGC 6642, and NGC 6717, respectively. The results are in excellent agreement with the literature for all sample clusters, considering the uncertainties. The present method of distance derivation, based on recent data of member RR Lyrae stars, updated BaSTI models, and robust statistical methods, proved to be consistent. A larger sample of clusters will be investigated in a future work.
- ID:
- ivo://CDS.VizieR/J/ApJ/824/74
- Title:
- OGLE LC classification of MC Cepheids
- Short Name:
- J/ApJ/824/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The investigation of the nonlinearity of the Leavitt law (LL) is a topic that began more than seven decades ago, when some of the studies in this field found that the LL has a break at about 10 days. The goal of this work is to investigate a possible statistical cause of this nonlinearity. By applying linear regressions to OGLE-II and OGLE-IV data, we find that to obtain the LL by using linear regression, robust techniques to deal with influential points and/or outliers are needed instead of the ordinary least-squares regression traditionally used. In particular, by using M- and MM-regressions we establish firmly and without doubt the linearity of the LL in the Large Magellanic Cloud, without rejecting or excluding Cepheid data from the analysis. This implies that light curves of Cepheids suggesting blending, bumps, eclipses, or period changes do not affect the LL for this galaxy. For the Small Magellanic Cloud, when including Cepheids of this kind, it is not possible to find an adequate model, probably because of the geometry of the galaxy. In that case, a possible influence of these stars could exist.
- ID:
- ivo://CDS.VizieR/J/AcA/65/297
- Title:
- OGLE4 LMC and SMC Cepheids
- Short Name:
- J/AcA/65/297
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present here a nearly complete census of classical Cepheids in the Magellanic System. The sample extends the set of Cepheids published in the past by the Optical Gravitational Lensing Experiment (OGLE) to the outer regions of the Large (LMC) and Small Magellanic Cloud (SMC). The entire collection consists of 9535 Cepheids of which 4620 belong to the LMC and 4915 are members of the SMC. We provide the I- and V-band time-series photometry of the published Cepheids, their finding charts, and basic observational parameters. Based on this unique OGLE sample of Cepheids we present updated period-luminosity relations for fundamental, first, and second mode of pulsations in the I- and V-bands and for the WI extinction-free Wesenheit index. We also show the distribution of classical Cepheids in the Magellanic System. The OGLE collection contains several classical Cepheids in the Magellanic Bridge - the region of interaction between the Magellanic Clouds. The discovery of classical Cepheids and their estimated ages confirm the presence of young stellar population between these galaxies.
- ID:
- ivo://CDS.VizieR/J/AcA/49/543
- Title:
- OGLE LMC & SMC Cepheids VI photometry
- Short Name:
- J/AcA/49/543
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We 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, recently published by the OGLE-II collaboration. Location of selected Cepheids on the sky indicates that many of them are very likely cluster members. Photometric data of Cepheids and clusters are available from the OGLE Internet archive at URL: ftp://sirius.astrouw.edu.pl/ogle/ogle2/clusters/cepheids/
