Wyniki wyszukiwania - Biblioteka Nauki

1

Large Magellanic Cloud Cepheids in the ASAS Data

100%

Karczmarek P. , Dziembowski W. A. , Lenz P. , Pietrukowicz P. , Pojmański G.

|

tom Vol. 61, No. 4

303--318

EN

A catalog of Cepheids in the Large Magellanic Cloud (LMC) from the ASAS project is presented. It contains data on 65 fundamental mode pulsators with periods longer than about 8 days. The period-luminosity (PL) relation in the V-band does not significantly differ from the relation determined from the OGLE-III data extended toward longer periods but shows much larger scatter. For objects with periods longer than 40 d there is an evidence for a shallower PL relation. The rates of long-term period variations significant at 3σ level are found only for seven objects. The rates for 25 objects determined with the 1σ significance are confronted with the values derived from stellar evolution models. The models from various sources yield discrepant predictions. Over the whole data range, a good agreement with measurements is found for certain models but not from the same source.

2

Metallicity Estimates for Double-Mode Cepheids from Photometry

100%

Szilàdi K. , Vinkò J. , Szabados L.

|

tom Vol. 68, No. 2

111--123

EN

We investigate the effect of different metallicities on the light curve shape of classical double-mode (beat) Cepheids pulsating in the fundamental and first overtone modes by correlating the light curve Fourier parameters with [Fe/H] ratios. We combine data of known Galactic beat Cepheids with those from both Magellanic Clouds assembled by the OGLE-III and OGLE-IV surveys. The [Fe/H] values for the Galactic sample are based on recent high-resolution spectroscopy. For the Magellanic sample we apply the metallicity-period-period ratio relationship to estimate individual [Fe/H] values. We confirm that the metallicity is most strongly correlated with the amplitude of the light curve and the amplitude ratio of the first and second harmonics (R21), similar to single-mode classical Cepheids found by Klagyivik. We also show that the metallicity is less correlated with φ31 parameter in our sample, as compared with the case of the RR Lyr type variables. We derive empirical formulae that can be used to estimate the [Fe/H] of classical Cepheids that extends well below the metallicity of the Milky Way disk, down to the lower metallicities of the Magellanic Clouds.

3

Additional Galactic Cepheids from the OGLE Survey

88%

Soszyński I. , Udalski A. , Szymański M. K. , Pietrukowicz P. , Skowron J. , Skowron D. M. , Poleski R. , Kozłowski S. , Mróz P. , Ulaczyk K. , Rybicki K. , Iwanek P. , Wrona M. , Gromadzki M.

|

tom Vol. 70, No. 2

101--119

EN

We report on the results of a comprehensive search for Cepheid variable stars in the fields photometrically monitored by the OGLE Galaxy Variability Survey. We identify 742 Cepheids not included in the first release of the OGLE Collection of Galactic Cepheids and reclassify several dozen previously published variables. The upgraded collection comprises 1974 classical, 1625 type II, and 119 anomalous Cepheids located in the area of about 3000 square degrees covering the disk and bulge of the Milky Way. We present the most interesting objects in our sample: an isolated group of long-period double-mode classical Cepheids pulsating in the fundamental mode and first overtone, the first known Galactic double-mode Cepheid with the second and third overtone excited, double-mode type II Cepheids, candidates for single-mode first-overtone BL Her stars, and Cepheids showing simultaneous eclipsing variability. We also discuss type II and anomalous Cepheids that are potential members of globular clusters.

4

The OGLE Collection of Variable Stars. Type II Cepheids in the Magellanic System

88%

Soszyński I. , Udalski A. , Szymański M. K. , Wyrzykowski Ł. , Ulaczyk K. , Poleski R. , Pietrukowicz P. , Kozłowski S. , Skowron D. , Skowron J. , Mróz P. , Rybicki K. , Iwanek P.

|

tom Vol. 68, No. 2

89--109

EN

We present a nearly complete collection of type II Cepheids in the Magellanic System. The sample consists of 338 objects: 285 and 53 variables in the Large and Small Magellanic Clouds, respectively. Based on the pulsation periods and light-curve morphology, we classified 118 of our type II Cepheids as BL Her, 120 as W Vir, 34 as peculiar W Vir, and 66 as RV Tau stars. For all objects, we publish time-series {\it VI} photometry obtained during the OGLE-IV survey, from 2010 to the end of 2017. We present the most interesting individual objects in our collection: 16 type II Cepheids showing additional eclipsing or ellipsoidal variability, two RV Tau variables more than 2.5 mag fainter than other stars of this type in the LMC, an RVb star that drastically decreased the amplitude of the long-period modulation, type II Cepheids exhibiting significant amplitude and period changes, and an RV Tau star which undergoes interchanges of deep and shallow minima. We show that peculiar W Vir stars have markedly different spatial distribution than other subclasses of type II Cepheids, which indicates different evolutionary histories of these objects.

5

The OGLE Collection of Variable Stars. Classical, Type II, and Anomalous Cepheids toward the Galactic Center

88%

Soszyński I. , Udalski A. , Szymański M. K. , Wyrzykowski Ł. , Ulaczyk K. , Poleski R. , Pietrukowicz P. , Kozłowski S. , Skowron D. M. , Skowron J. , Mróz P. , Pawlak M. , Rybicki K. , Jacyszyn-Dobrzeniecka A.

|

tom Vol. 67, No. 4

297--316

EN

We present a collection of classical, typeII, and anomalous Cepheids detected in the OGLE fields toward the Galactic center. The sample contains 87 classical Cepheids pulsating in one, two or three radial modes, 924 type II Cepheids divided into BL Her, W Vir, peculiar W Vir, and RV Tau stars, and 20 anomalous Cepheids - first such objects found in the Galactic bulge. Additionally, we upgrade the OGLE Collection of RR Lyr stars in the Galactic bulge by adding 828 newly identified variables. For all Cepheids and RRLyr stars, we publish time-series VI photometry obtained during the OGLE-IV project, from 2010 through 2017. We discuss basic properties of our classical pulsators: their spatial distribution, light curve morphology, period-luminosity relations, and position in the Petersen diagram. We present the most interesting individual objects in our collection: a typeII Cepheid with additional eclipsing modulation, WVir stars with the period doubling effect and the RVb phenomenon, a mode-switching RR Lyr star, and a triple-mode anomalous RRd star.

6

Final Release of the OGLE Collection of Cepheids and RR Lyrae Stars in the Magellanic System. The Outer Regions

88%

Soszyński I. , Udalski A. , Szymański M. K. , Pietrukowicz P. , Skowron J. , Skowron D. M. , Poleski R. , Kozłowski S. , Mróz P. , Ulaczyk K. , Rybicki K. , Iwanek P. , Wrona M.

|

tom Vol. 69, No. 2

87--99

EN

We present the final release of the OGLE collection of classical pulsators (Cepheids and RR Lyr stars) in the Large and Small Magellanic Clouds. The sky coverage has been increased from 670 to 765 square degrees compared to the previous edition of our collection. We also add some Cepheids and RR Lyr stars found by the Gaia team and reclassify three Cepheids. Ultimately, our collection consists of 9650 classical Cepheids, 343 type II Cepheids, 278 anomalous Cepheids, and 47 828 RR Lyr stars inside and toward the Magellanic System.