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- 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)
- 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.
7347. 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.
- ID:
- ivo://CDS.VizieR/J/AJ/140/844
- Title:
- UCAC3 proper motion survey
- Short Name:
- J/AJ/140/844
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents 442 new proper motion stellar systems in the southern sky between declinations -90{deg} and -47{deg} with 0.40"/yr>{mu}>=0.18"/yr. These systems constitute a 25.3% increase in new systems for the same region of the sky covered by previous SuperCOSMOS RECONS (SCR) searches that used Schmidt plates as the primary source of discovery. Among the new systems are 25 multiples, plus an additional 7 new common proper motion (CPM) companions to previously known primaries. All stars have been discovered using the third U.S. Naval Observatory (USNO) CCD Astrograph Catalog (UCAC3). A comparison of the UCAC3 proper motions to those from the Hipparcos, Tycho-2, Southern Proper Motion (SPM4), and SuperCOSMOS efforts is presented and shows that UCAC3 provides similar values and precision to the first three surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/745/118
- Title:
- UCAC3 proper motion survey. II. -47<DEC<0{deg}
- Short Name:
- J/ApJ/745/118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 474 new proper motion stellar systems (500 objects) in the southern sky having no previously known components, with 0.40"/yr>{mu}>=0.18"/yr between declinations -47{deg} and 0{deg}. In this second paper utilizing the U.S. Naval Observatory third CCD Astrograph Catalog (UCAC3) we complete our sweep of the southern sky for objects in the proper motion range targeted by this survey with R magnitudes ranging from 9.80 to 19.61. The new systems contribute a ~16% increase in the number of new stellar systems for the same region of sky reported in previous SuperCOSMOS Research Consortium On Nearby Stars (RECONS) surveys. Among the newly discovered stellar systems are 16 multiples, plus an additional ten components that are new common proper motion companions to previously known objects. A comparison of UCAC3 proper motions to those from Hipparcos, Tycho-2, Southern Proper Motion, and SuperCOSMOS indicates that all proper motions are consistent to ~10mas/yr, with the exception of SuperCOSMOS. Distance estimates are derived for all stellar systems having SuperCOSMOS Sky Survey B_J_, R_59F_, and I_IVN_ plate magnitudes and Two Micron All Sky Survey (2MASS) infrared photometry. We find five new red dwarf systems estimated to be within 25pc. These discoveries support results from previous proper motion surveys suggesting that more nearby stellar systems are to be found, particularly in the fainter, slower moving samples. In this second paper utilizing the UCAC3 we complete our sweep of the southern sky for objects in the proper motion range targeted by this survey with R magnitudes ranging from 9.80 to 19.61.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/86
- Title:
- UCD galaxies in the Coma cluster
- Short Name:
- J/ApJ/737/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have undertaken a spectroscopic search for ultra-compact dwarf galaxies (UCDs) in the dense core of the dynamically evolved, massive Coma cluster as part of the Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) Coma Cluster Treasury Survey. UCD candidates were initially chosen based on color, magnitude, degree of resolution within the ACS images, and the known properties of Fornax and Virgo UCDs. Follow-up spectroscopy with Keck/Low-Resolution Imaging Spectrometer confirmed 27 candidates as members of the Coma cluster, a success rate >60% for targeted objects brighter than M_R_=-12. Another 14 candidates may also prove to be Coma members, but low signal-to-noise spectra prevent definitive conclusions.
