- ID:
- ivo://CDS.VizieR/J/A+AS/128/265
- Title:
- ubvy-beta photometry of CP2 stars
- Short Name:
- J/A+AS/128/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this work is to study the capacity of the uvby H_{beta}_ system for detecting the chemically peculiar (CP) stars based on the effect that peculiar features in the flux distribution have on all the Stroemgren-Crawford indices. Our study focuses on the classical magnetic peculiar stars (CP2), though Am star s (CP1) are also included for comparison with cool CP2 stars. Satisfactory results were obtained for hot CP2 stars: the definition of a new index p, which is a linear combination of uvby H_{beta}_ colours, allowed us to separate a high percentage of hot CP2 stars from normal stars. According to this new index, 60 new CP2 candidates are proposed. The working sample was extracted from The General Catalogue of Ap and Am stars by Renson et al. (1991, Cat. <III/162>). Photometric observations to enlarge the sample of CP2 stars with complete uvby H_{beta}_ photometry were carried out. These observations are also reported in the present paper. The new index p is also used to correct the reddening of early CP2 stars computed as if they were normal stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/372/477
- Title:
- ubvy{beta} photometry of h & chi Persei
- Short Name:
- J/A+A/372/477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present uvby{beta} CCD photometry of the central region of the double cluster h&{chi} Persei. We identify =~350 stars, of which 214 were not included in Oosterhof's catalogue. Our magnitude limit V=16.5 allows us to reach early F spectral type and obtain very accurate fits to the ZAMS. We derive reddening values of E(b-y)=0.44+/-0.02 for h Persei and E(b-y)=0.39+/-0.05 for {chi} Persei. From the ZAMS fitting, we derive distance moduli V_0_-M_V_=11.66+/-0.20 and V_0_-M_V_=11.56+/-0.20 for h and {chi} Persei respectively. These values are perfectly compatible with both clusters being placed at the same distance and having identical reddenings. The shift in the main-sequence turnoff and isochrone fitting, however, show that there is a significant age difference between both clusters, with the bulk of stars in h Persei being older than {chi} Persei. There is, however, a significant population of stars in h Persei which are younger than {chi} Persei. All this argues for at least three different epochs of star formation, corresponding approximately to logt=7.0, 7.15 and 7.3.
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/44.111
- Title:
- ubvy{beta} photometry of NGC 6882/5 stars
- Short Name:
- J/other/RMxAA/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Unpublished uvby-{beta} photoelectric photometry of the open cluster NGC 6882/5 is presented. Utilizing already tested distance determinations through photometric techniques, it is found that there are at least two distinct star accumulations in the direction of the open cluster NGC 6882/5. A brief discussion is made of the nature of the previously found short period variables.
- ID:
- ivo://CDS.VizieR/J/AcA/59/69
- Title:
- ubvy{beta} photometry of stars in NGC 7062
- Short Name:
- J/AcA/59/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results of spectroscopic and photometric observations of ten delta Sct stars and one eclipsing binary in the open cluster NGC 1817, and of ten delta Sct stars and two other variables in the open cluster NGC 7062. For all targets in NGC 1817 and for three targets in NGC 7062 the radial velocity and projected rotational velocity are determined. For all stars the effective temperature and surface gravity is measured.
- ID:
- ivo://CDS.VizieR/J/A+A/426/827
- Title:
- ubvyH{beta} photometry in NGC 1817 / 1807
- Short Name:
- J/A+A/426/827
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalogue of accurate uvby-H{beta} and J2000 coordinates for 7842 stars in an area of 65'x40' around NGC 1817. We mark the selection of probable members of NGC 1817, combining this photometric study with the previous astrometric analysis (Balaguer-Nunez et al. 2004, Cat. <J/A+A/426/819>). Also given is the cross-identification of stars in common with the astrometry (Balaguer-Nunez et al. 2004, Cat. <J/A+A/426/819>), WEBDA (http://obswww.unige.ch/WEBDA), Hipparcos (ESA, 1997, Cat. <I/239>), Tycho-2 (Hog et al., 2000, Cat. <I/250>) and USNO-A2 (Monet et al., 1998, Cat. <I/252>) catalogues.
- 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.
- 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.
- 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/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.
5470. UCAC4 nearby star survey
- ID:
- ivo://CDS.VizieR/J/AJ/148/119
- Title:
- UCAC4 nearby star survey
- Short Name:
- J/AJ/148/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use data from the U.S. Naval Observatory fourth CCD Astrograph Catalog (UCAC4) in combination with photometry from the AAVSO Photometric All-Sky Survey and Two Micron All-Sky Survey to identify stars within 25pc of the Sun. A sample of nearby stars with accurate trigonometric parallaxes from the Research Consortium On Nearby Stars is used to generate a set of 16 new photometric color-M_K_ relations that provide distance estimates with uncertainties of 15%. This work expands the available suites of well-calibrated photometric distance relations that can be used to identify nearby stellar systems. The distance relations are used with quality cuts to extract an initial sample of stars from the UCAC4 estimated to be within 25pc. Color, proper motion, and existing literature sources are then used to obtain a clean sample of red dwarfs, while limiting the amount of contamination from background giants, resulting in a sample of 1761 candidate nearby stars within 25pc. Of these, 339 are new discoveries with no previously known published parallax or distance estimate, primarily with proper motions less than 0.2arcsec/yr. Five stars are estimated to be within 10pc, with the nearest, TYC 3980 1081 1, with V=10.50 estimated to be at 5.9pc. That several hundred new stars have been revealed so close to the Sun illustrates once again that there is considerable work yet to be done to map the solar neighborhood and that additional nearby stars are likely still to be discovered.
