- ID:
- ivo://CDS.VizieR/J/A+A/525/A16
- Title:
- ubvy light curves of CP stars in open clusters
- Short Name:
- J/A+A/525/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric variability of chemically peculiar (CP) stars of the upper main sequence is closely connected to their local stellar magnetic field and their rotational period. Long term investigations, as presented here, help us to identify possible stellar cycles (as in the Sun). Photoelectric Stroemgren uvby time series for 27 CP stars within the boundaries of open clusters are presented. Our observations cover a time period of about six years (1986 to 1992) with typically fifteen measurements for each objects. These observations help us to determine the rotational periods of these objects. We established, for the first time, variability for fourteen CP stars. For additional two stars, a merging of already published data sets, resulted in more precise periods, whereas for six objects, the published periods could be confirmed. Last, but not least, no significant variations were found for five stars. Apart from six stars, all targets seem to be members of their host open clusters.
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- ID:
- ivo://CDS.VizieR/J/A+A/364/205
- Title:
- UBVy photometry of cool stars
- Short Name:
- J/A+A/364/205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-precision photometry, high- and medium-resolution spectroscopy for a sample of 32 stars likely to be the optical counterparts of X-ray sources serendipitously detected by the EXOSAT satellite. Using also recent results from the Hipparcos satellite, we infer spectral types, compute X-ray luminosities and Li abundances and investigate the single or binary nature of the sample stars. We found eleven new variable stars, whose photometric periods fall in the 1.2-27.5 day range, for most of which the optical variability is consistent with the presence of photospheric cool spots. For our sample of X-ray selected stars we confirm the existence of a strong correlation between the stellar rotation rate and the level of activity, and also between the X-ray and bolometric luminosities. Two stars in our sample are likely to be pre-main sequence objects, one is likely to be a previously unknown M-type star within 25pc.
21623. ubvy photometry of CR Cas
- ID:
- ivo://CDS.VizieR/J/A+AS/128/139
- Title:
- ubvy photometry of CR Cas
- Short Name:
- J/A+AS/128/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The table contains the differential magnitudes of CR Cas respect to comparison star SAO35044 indicating the time (Julian Date) a nd magnitudes in Stroemgren filters u, v, b, y
- ID:
- ivo://CDS.VizieR/J/A+A/364/455
- Title:
- ubvy photometry of LMC/SMC B stars
- Short Name:
- J/A+A/364/455
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The individual reddenings for B stars in two fields in the Small Magellanic Cloud (SMC) and two fields in the Large Magellanic Cloud (LMC) are determined by means of Stroemgren uvby CCD photometry. In both LMC fields we find a foreground reddening of E(B-V)=0.085+/-0.02, and for the SMC fields we find E(B-V)=0.070+/-0.02. In addition to the foreground reddening we find contributions from reddening intrinsically in the Clouds up to E(B-V)~0.21. The intrinsic contribution is not correlated with position within our ~6'x4.5' CCD fields but varies in an essentially random way. Unless the reddening is measured for a particular object, it will be uncertain by +/-0.035 (best case, far from the central bars) to more than +/-0.10 (close to the central bars). The Stroemgren uvby photometry has been used to derive metallicities for GK giant stars in the observed fields. Adopting average reddenings we obtain mean metallicities which are consistent with those found from spectroscopic studies of F and G supergiants (Westerlund, 1997, The Magellanic Clouds, Cambridge University Press), but with a considerable scatter in the derived metallicities, from [Fe/H]=~-2.0 to [Fe/H]>0. A significant fraction of the scatter is, however, due to reddening variations rather than being intrinsic. The possible existence of high metallicity stars should be investigated further using spectroscopic methods.
- ID:
- ivo://CDS.VizieR/J/A+A/435/1099
- Title:
- ubvy photometry of 4 magnetic CP stars
- Short Name:
- J/A+A/435/1099
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Differential Stroemgren uvby observations from the Four College Automated Photoelectric Telescope are presented for the magnetic Chemically Peculiar (mCP) stars HD 32633, Aur, 49 Cam, and 3 Hya. We find for over 30 years, these four stars with stable optical region light curves have had constant periods of 6.4300, 3.61868, 4.28679, and 11.305 days, respectively.
- ID:
- ivo://CDS.VizieR/J/A+AS/103/1
- Title:
- ubvy Photometry of magnetic CP stars
- Short Name:
- J/A+AS/103/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Differential Stroemgren uvby photometric observations from the Four College Automated Photoelectric Telescope of four magnetic Chemically Peculiar stars are presented. We refined the period of 63 And to 4.1890 days. The period of the sharp-lined Si star HD 192913 is 16.840 days, a value close to, but slightly different from published values. HR 8240, a sharp-lined Si star, is found not to be a photometric variable. Comparison of four color photometry of 108 Aqr by Morrison and Wolff and from the Four College APT indicates that subtle changes in the shapes of the light curves, especially that for u, have occurred suggesting that this star may be precessing.
- ID:
- ivo://CDS.VizieR/J/A+A/357/548
- Title:
- ubvy Photometry of magnetic CP stars
- Short Name:
- J/A+A/357/548
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Differential Stroemgren uvby photometric observations from the Four College Automated Photoelectric Telescope (FCAPT) are presented for the magnetic CP stars HD 36668, 36 Lyn, HD 86592, and HR 8861. Using the FCAPT values, North's period for HD 36668 is refined to 2.11884 days. The 3.834 day period of Shore et al. (1990ApJ...348..242S) for 36 Lyn, which was found from magnetic field measurements, is confirmed by photometry. The FCAPT observations also support the 2.8867 day period of Babel & North (1997A&A...325..195B) for HD 86592, demonstrate that this star is a large amplitude variable in v (0.13 mag), and show that y varies crudely out of phase from u, v, and b which are in phase with one another. The variability of HR 8861 appears to be correlated with the meridional passages of regions of Si over- and underabundance as found by Piskunov et al. (1994A&A...291..910P)
21628. ubvy photometry of NGC2419
- ID:
- ivo://CDS.VizieR/J/A+A/581/A72
- Title:
- ubvy photometry of NGC2419
- Short Name:
- J/A+A/581/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 2419 is a peculiar Galactic globular cluster offset from the others in the size-luminosity diagram, and showing several chemical abundance anomalies. Here, we present Stromgren uvby photometry of the cluster. Using the gravity- and metallicity-sensitive c1 and m1 indices, we identify a sample of likely cluster members extending well beyond the formal tidal radius. The estimated contamination by cluster non-members is only one per cent, making our catalogue ideally suited for spectroscopic follow-up. We derive photometric [Fe/H] of red giants, and depending on which metallicity calibration from the literature we use, we find reasonable to excellent agreement with spectroscopic [Fe/H], both for the cluster mean metallicity and for individual stars. We demonstrate explicitly that the photometric uncertainties are not Gaussian and this must be accounted for in any analysis of the metallicity distribution function.
21629. UCAC5 Catalogue
- ID:
- ivo://CDS.VizieR/I/340
- Title:
- UCAC5 Catalogue
- Short Name:
- I/340
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New astrometric reductions of the US Naval Observatory CCD Astrograph Catalog (UCAC) all-sky observations were performed from first principles using the TGAS stars in the 8 to 11 magnitude range as reference star catalog. Significant improvements in the astrometric solutions were obtained and the UCAC5 catalog of mean positions at a mean epoch near 2001 was generated. By combining UCAC5 with Gaia DR1 data new proper motions on the Gaia coordinate system for over 107 million stars were obtained with typical accuracies of 1 to 2mas/yr (R=11 to 15mag), and about 5mas/yr at 16th mag. Proper motions of most TGAS stars are improved over their Gaia data and the precision level of TGAS proper motions is extended to many millions more, fainter stars. External comparisons were made using stellar cluster fields and extragalactic sources. The TGAS data allow us to derive the limiting precision of the UCAC x, y data, which is significantly better than 1/100 pixel.
21630. UCAC2 Catalogue
- ID:
- ivo://CDS.VizieR/I/289
- Title:
- UCAC2 Catalogue
- Short Name:
- I/289
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UCAC2 is the second release of the ongoing UCAC project, designed to observe the entire sky for R magnitudes of about 7.5 to 16. The observed positional errors are about 20 mas for the stars in the 10-14 magnitude range, and about 70 mas at the limiting magnitude of R~16. For up-to-date information on the project, see the UCAC web page at http://ad.usno.navy.mil/ucac/ . This web page will also serve as the location that the UCAC team will post addenda to the UCAC2 catalog. The UCAC2 is a high density, highly accurate, astrometric catalog of 48,330,571 stars covering the sky from -90 to +40 degrees in declination and going up to +52 degrees in some areas. The northern limit is a function of right ascension. Proper motions and photometry are provided for all stars. Positions and proper motions are on the ICRS (International Celestial Reference System) and given at the epoch J2000.0. The UCAC2 has a number of major differences with respect to UCAC1. These differences include: - much larger sky coverage - reduced systematic errors of CCD observations - positions given at a standard epoch (J2000.0) - the addition of several new catalogs for improved proper motions - photometry in the J, H, and K_s bands from the 2MASS project Additional details of the data are found in Sections 3, 4, and 5 of the "readme.txt" file. UCAC2 is the last intermediate data release before the final, all sky catalog will be constructed. Observations will end around mid 2004; the final catalog is expected out in 2005. The UCAC project, observations, and first data release are described in detail in the paper Zacharias et al. AJ 120, 2131 (2000). Versions of that and other related papers are placed on the UCAC Web page (http://ad.usno.navy.mil/ucac/). The paper describing UCAC2 is in preparation (AJ, 2003); some further details can be found in the "readme.txt" file.
