- ID:
- ivo://CDS.VizieR/J/AcA/60/295
- Title:
- VI photometry of Galactic disk field stars
- Short Name:
- J/AcA/60/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present OGLE-III Photometric Maps of the Galactic disk fields observed during the OGLE-III campaigns for low luminosity transiting objects that led to the discovery of the first transiting exoplanets. The maps contain precise, calibrated VI photometry of about 9 million stars from 21 OGLE-III fields in the Galactic disk observed in the years 2002-2009 and covering more than 7 square degrees in the sky. Precise astrometry of these objects is also provided. We discuss quality of the data and present a few color-magnitude diagrams of the observed fields.
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- ID:
- ivo://CDS.VizieR/J/AcA/53/27
- Title:
- VI photometry of MM1 and MM7 OGLE fields
- Short Name:
- J/AcA/53/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a result of the reanalysis of the OGLE-I observations by means of the image subtraction method, we present the first part of a catalog, consisting of data for variable stars in four Galactic fields observed by OGLE-I, viz. MM1-A, MM1-B, MM7-A, and MM7-B. In total, 2016 variable stars have been found. This increased the number of known variable stars in these fields more than twofold. We comment on the detectability of the variable stars in previous studies.
- ID:
- ivo://CDS.VizieR/J/ApJ/523/540
- Title:
- VI photometry of new Cepheids in NGC 3319
- Short Name:
- J/ApJ/523/540
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distance to NGC 3319 has been determined from Cepheid variable stars as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Thirteen and four epochs of observations, using filters F555W (V) and F814W (I), respectively, were made with the Wide Field Planetary Camera 2. Thirty-three Cepheid variables between periods of 8 and 47 days were discovered. Adopting a Large Magellanic Cloud distance modulus of 18.50{+/-}0.10 mag and extinction of E(V-I)=0.13 mag, a true reddening-corrected distance modulus (based on an analysis employing the ALLFRAME software package) of 30.78 {+/-}0.14 (random) {+/-}0.10 (systematic) mag and the extinction of E(V-I)=0.06 mag were determined for NGC 3319. This galaxy is the last galaxy observed for the HST H_o_ Key Project.
- ID:
- ivo://CDS.VizieR/J/ApJ/514/614
- Title:
- VI photometry of new Cepheids in NGC 3198
- Short Name:
- J/ApJ/514/614
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of Cepheid variable stars and a new distance to the Sc spiral NGC 3198. NGC 3198 is one of 25 galaxies that have been observed with the WFPC2 of the Hubble Space Telescope (HST) for the purpose of measuring Cepheid distances. Eighteen of these galaxies were targeted by the HST Key Project on the Extragalactic Distance Scale, whose objective is to calibrate a variety of secondary distant indicators and determine the Hubble constant to an accuracy of 10%. NGC 3198 was selected as part of this sample because its type and orientation make it very suitable as a Tully-Fisher calibrator. The WFPC2 data are comprised of 13 epochs in F555W ({~}V) and five epochs in F814W ({~}I). Two different crowded-field photometry packages (DAOPHOT/ALLFRAME and DoPHOT) were used. The magnitudes derived from these two packages agree to within a few percent. We identified 78 Cepheid candidates in the period range from eight to >50 days, of which 52 were selected for establishing the distance modulus. Period-luminosity relations were constructed in Johnson V and Kron-Cousins I by transforming the F555W and F814W to the standard system. We adopted a distance modulus of {mu}_o_=18.50{+/-}0.10 mag and mean reddening of E(B-V)=0.10 mag to the Large Magellanic Cloud Cepheids and found a true distance modulus to NGC 3198 of {mu}_o_=30.80{+/-}0.16 (random) {+/-}0.12 (systematic) mag. This modulus corresponds to a distance of 14.5 Mpc, with random and systematic errors of {+/-}1.2 and {+/-}0.9 Mpc, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/507/655
- Title:
- VI photometry of new Cepheids in NGC 2541
- Short Name:
- J/ApJ/507/655
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of Cepheids and a new distance to the spiral galaxy NGC 2541, based on data obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST). A total of 25 exposures (divided into 13 epochs) were obtained using the F555W filter (transformed to Johnson V), and nine exposures were obtained (divided into five epochs) using the F814W filter (transformed to Cousins I). Photometric reduction of the data is performed using two independent packages, DoPHOT and DAOPHOT II/ALLFRAME, which give very good agreement in the measured magnitudes. A total of 34 bona fide Cepheids, with periods ranging from 12 to over 60 days, are identified based on both sets of photometry. By fitting V and I period-luminosity relations, apparent distance moduli are derived assuming a Large Magellanic Cloud distance modulus and mean color excess of {mu}_LMC_=18.50+/-0.10mag and E(B-V)=0.10mag, respectively. Adopting A(V)/E(V-I)=2.45, we obtain a true distance modulus to NGC 2541 of {mu}_0_=30.47+/-0.11 (random) +/-0.12 (systematic) mag (D=12.4+/-0.6 [random] +/-0.7 [systematic] Mpc), and a total (Galactic plus internal) mean color excess E(B-V)=0.08+/-0.05 (internal error) mag.
- ID:
- ivo://CDS.VizieR/J/ApJ/512/48
- Title:
- VI photometry of new Cepheids in NGC 4725
- Short Name:
- J/ApJ/512/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distance to NGC 4725 has been derived from Cepheid variables as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Thirteen F555W (V) and four F814W (I) epochs of cosmic-ray-split Wide Field and Planetary Camera 2 observations were obtained. Twenty Cepheids were discovered, with periods ranging from 12 to 49 days. Adopting a Large Magellanic Cloud distance modulus and extinction of 18.50{+/-}0.10 mag and E(V-I)=0.13 mag, respectively, a true reddening-corrected distance modulus (based on an analysis employing the ALLFRAME software package) of 30.50{+/-}0.16 (random) {+/-}0.17 (systematic) mag was determined for NGC 4725. The corresponding of distance of 12.6{+/-}1.0 (random) {+/-}1.0 (systematic) Mpc is in excellent agreement with that found with an independent analysis based upon the DoPHOT photometry package. With a foreground reddening of only E(V-I)=0.02, the inferred intrinsic reddening of this field in NGC 4725, E(V-I)=0.19, makes it one of the most highly reddened fields encountered by the HST Key Project to date.
- ID:
- ivo://CDS.VizieR/J/A+A/507/803
- Title:
- VI photometry of new M53 variables
- Short Name:
- J/A+A/507/803
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the variable star content of the globular cluster M53 to compute the physical parameters of the constituting stars and the distance of the cluster. Covering two adjacent seasons in 2007 and 2008, new photometric data are gathered for 3048 objects in the field of M53. By using the OIS (optimal image subtraction) method and subsequently TFA (trend filtering algorithm), we search for variables in the full sample by using discrete Fourier transformation and box-fitting least squares method. We select variables based on the statistics related to these methods combined with visual inspection. We identified 12 new variables (2 RR Lyrae stars, 7 short periodic stars - 3 of them are SX Phe stars - and 3 long-period variables). No eclipsing binaries were found in the present sample. Except for the 3 (hitherto unknown) Blazhko RR Lyrae (two RRab and an RRc) stars, no multiperiodic variables were found. We showed that after proper period shift, the PLC (period-luminosity-color) relation for the first overtone RR Lyrae sample tightly follows the one spanned by the fundamental stars. Furthermore, the slope is in agreement with that derived from other clusters. Based on the earlier Baade-Wesselink calibration of the PLC relations, the derived reddening-free distance modulus of M53 is 16.31+/-0.04mag, corresponding to a distance modulus of 18.5mag for the Large Magellanic Cloud. From the Fourier parameters of the RRab stars we obtained an average iron abundance of -1.58+/-0.03 (error of the mean). This is ~0.5dex higher than the overall abundance of the giants as given in the literature and derived in this paper from the three-color photometry of giants. We suspect that the source of this discrepancy (observable also in other, low-metallicity clusters) is the lack of a sufficient number of low-metallicity objects in the calibrating sample of the Fourier method.
- ID:
- ivo://CDS.VizieR/J/AJ/125/1261
- Title:
- VI photometry of Sextans A Cepheids
- Short Name:
- J/AJ/125/1261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 82 short-period variable stars in Sextans A from deep Wide Field Planetary Camera 2 observations. All the periodic variables appear to be short-period Cepheids, with periods as small as 0.8 days for fundamental mode Cepheids and 0.5 days for first-overtone Cepheids. These objects have been used, along with measurements of the red giant branch (RGB) tip and red clump, to measure a true distance modulus to Sextans A of {mu}0=25.61+/-0.07, corresponding to a distance of d=1.32+/-0.04Mpc. Comparing distances calculated by these techniques, we find that short-period Cepheids (P<2-days) are accurate distance indicators for objects at or below the metallicity of the Small Magellanic Cloud. As these objects are quite numerous in low-metallicity star-forming galaxies, they have the potential for providing extremely precise distances throughout the Local Group. We have also compared the relative distances produced by other distance indicators. We conclude that calibrations of RR Lyrae stars, the RGB tip, and the red clump are self-consistent, but that there appears to be a small dependence of long-period Cepheid distances on metallicity. Finally, we present relative distances of Sextans A, Leo A, IC 1613, and the Magellanic Clouds.
- ID:
- ivo://CDS.VizieR/J/A+AS/118/303
- Title:
- VI Photometry of variables in NGC 2243
- Short Name:
- J/A+AS/118/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tables 3-13 contain V and I band light curves for 6 variables reported in the paper. Tables 14 and 15 contain VI photometry presented in Figs. 5 and 9, respectively.
- ID:
- ivo://CDS.VizieR/J/AJ/123/840
- Title:
- VI photometry of variable stars in Fornax
- Short Name:
- J/AJ/123/840
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a search for variable stars in the Fornax dwarf galaxy covering an area of half a square degree. We have ~30 epochs of VI data. We found and determined periods for more than 500 RR Lyrae, 17 anomalous Cepheids, and six Population II Cepheids. In addition we have 85 candidate long-period variables, the majority of which were previously unknown. We estimate that the average metal abundance of RR Lyrae stars is [Fe/H]~=-1.6dex.
