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16181. UBVRI CCD photometry of the open cluster NGC 6811
ID:
ivo://CDS.VizieR/J/AJ/145/7
Title:
UBVRI CCD photometry of the open cluster NGC 6811
Short Name:
J/AJ/145/7
Date:
21 Oct 2021
Publisher:
CDS
Description:
NGC 6811 is one of the four open clusters located in the Kepler spacecraft field of view. We obtained UBVRI photometry of the cluster on six nights (four of them photometric) with the 1.08m Hall and 1.83m Perkins telescopes at Lowell Observatory. The mean photometric precision ranges from better than 0.01mag in the V, B-V, V-R, and V-I indices among stars brighter than magnitude 15 to about 0.05mag for U-B at magnitude 18. We followed a Bayesian statistical approach using the Markov Chain Monte Carlo algorithm to determine the cluster reddening, distance, age, and iron content from a maximum-likelihood fit to stellar isochrones. Using the Yale-Yonsei isochrones, we derived E(B-V)=0.066+/-0.025, (m-M)_V_=10.13+/-0.19, age=1.06+/-0.19Gyr, and Z=0.012+/-0.004 ([Fe/H]=-0.18); with the Padova isochrones, we found E(B-V)=0.081+/-0.015, (m-M)_V_=10.31+/-0.11, age=0.94+/-0.08Gyr, and Z=0.012+/-0.002 ([Fe/H]=-0.20). The uncertainties include possible errors in the photometric zero points of +/-0.01mag, but do not include uncertainties in the models. Taking into account the differences between the two sets of models, we find the best estimate for the cluster parameters to be E(B-V)=0.074+/-0.024, (m-M)_V_=10.22+/-0.18, age=1.00+/-0.17Gyr, and Z=0.012+/-0.004 ([Fe/H]=-0.19).
16182. UBVRI CCD sequences for wide-field surveys. I.
ID:
ivo://CDS.VizieR/J/MNRAS/276/33
Title:
UBVRI CCD sequences for wide-field surveys. I.
Short Name:
J/MNRAS/276/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first results of a campaign to secure deep UBVRI CCD photometric calibration in all UK Schmidt equatorial fields with galactic latitudes |b|<~50{deg}. In this paper we provide information on deep BVRI sequences (B<22mag) in 14 UK Schmidt survey fields centred at declination=0{deg}. Deep U sequences have been obtained for 11 of these fields.
16183. UBV(RI)cHalpha photometry in omega Cen
ID:
ivo://CDS.VizieR/J/A+A/493/959
Title:
UBV(RI)cHalpha photometry in omega Cen
Short Name:
J/A+A/493/959
Date:
21 Oct 2021
Publisher:
CDS
Description:
omega Centauri is the most well studied Galactic Globular Cluster because of its numerous puzzling features: significant dispersion in metallicity, multiple populations, triple main-sequence, horizontal branch morphology, He-rich population(s), and extended star-formation history. Intensive spectroscopic follow-up observing campaigns targeting stars at different positions in the color-magnitude diagram promises to clarify some of these peculiarities. To be able to target cluster members reliably during spectroscopic surveys and both spatial and radial distributions in the cluster outskirts without including field stars, a high quality proper-motion catalog of omega Cen and membership probability determination are required. The only available wide field proper-motion catalog of omega Cen is derived from photographic plates, and only for stars brighter than B~16. Using ESO archive data, we create a new, CCD-based, proper-motion catalog for this cluster, extending to B~20. We used high precision astrometric software developed specifically for data acquired by WFI@2.2m telescope and presented in the first paper of this series.
16184. UBVRIcJHKL photometry in Lup
ID:
ivo://CDS.VizieR/J/A+A/320/185
Title:
UBVRIcJHKL photometry in Lup
Short Name:
J/A+A/320/185
Date:
21 Oct 2021
Publisher:
CDS
Description:
In a recent study, some 130 new weak-line T Tauri stars (WTTS) have been discovered in the Lupus star forming region (SFR). Some of these stars are seen projected onto regions of high obscuration, while others are located far from the Lupus dark clouds. In this paper we present photometric observations of a large sample of these WTTS. We estimate effective temperatures and luminosities for the stars observed, and derive masses and ages by comparison with theoretical evolutionary tracks. The photometric observations were performed at the ESO 1 m-Telescope during two observing runs in 1993 (March 10-12) and 1994 (May 1-6) at ESO, La Silla. The typical standard deviations are 0.01mag in V, 0.02mag in B-V, 0.04mag in U-B, 0.01 in V-R and V-I. For a description of the UBV, (RI)c and JHKL photometric systems, see e.g. <GCPD/01>, <GCPD/54> and <GCPD/09>
16185. UBV(RI)cJHK photometry of NGC 2401
ID:
ivo://CDS.VizieR/J/MNRAS/367/1441
Title:
UBV(RI)cJHK photometry of NGC 2401
Short Name:
J/MNRAS/367/1441
Date:
21 Oct 2021
Publisher:
CDS
Description:
Based on a deep optical CCD (UBV(RI)_C) photometric survey and on the Two-Micron All-Sky-Survey (2MASS, <II/246>) data we derived the main parameters of the open cluster NGC 2401. We found this cluster is placed at 6.3+/-0.5kpc (Vo-Mv=14.0+/-0.2) from the Sun and is 25Myr old, what allows us to identify NGC 2401 as a member of the young population belonging to the innermost side of the extension of the Norma-Cygnus spiral-arm in the Third Galactic Quadrant. A spectroscopic study of the emission star LSS 440 that lies in the cluster area revealed it is a B0Ve star; however, we could not confirm it is a cluster member. We also constructed the cluster luminosity function (LF) down to V~22 and the cluster initial mass function (IMF) for all stars with masses above M~1-2M_{sun}_. It was found that the slope of the cluster IMF is x~1.8+/-0.2. The presence of a probable PMS star population associated to the cluster is weakly revealed.
16186. UBV(RI)c light curves of BD+66 1663
ID:
ivo://CDS.VizieR/J/AZh/87/462
Title:
UBV(RI)c light curves of BD+66 1663
Short Name:
J/AZh/87/462
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained the first UBV(RI)C photoelectric light curves of the recently discovered eclipsing binary BD+66 1663 = GSC 4479 412 (P=7.04d, V=10.14). We have derived relative and absolute parameters of the binary, and analyzed the interstellar extinction towards the object. Though the star is located in the field of the young open cluster Be 59, we demonstrate that it is not a member.
16187. UBV(RI)c phot. of omega Cen (NGC5139) subgiants
ID:
ivo://CDS.VizieR/J/ApJ/663/296
Title:
UBV(RI)c phot. of omega Cen (NGC5139) subgiants
Short Name:
J/ApJ/663/296
Date:
21 Oct 2021
Publisher:
CDS
Description:
We combine spectroscopic and photometric data for subgiant stars of {omega} Cen to extract results that neither data set could have provided on its own. GIRAFFE@VLT spectra of 80 stars at R=6400 give metallicities for all of them and abundances of C, N, Ca, Ti, and Ba for a subset of them. The photometric data, which have unusually high accuracy, come from a ~10x10arcmin^2^ mosaic of HST ACS images centered on the cluster center and on multicolor images of a ~34x33arcmin^2^ field, taken with the WFI@ESO2.2m camera. Stars with [Fe/H]<-1.25 have a large magnitude spread on the flat part of the sub-giant branch (SGB). We interpret this as empirical evidence for an age spread, and from theoretical isochrones we derive a relative age for each star.
16188. UBV(RI)c photometry of active stars. IX
ID:
ivo://CDS.VizieR/J/A+A/367/910
Title:
UBV(RI)c photometry of active stars. IX
Short Name:
J/A+A/367/910
Date:
21 Oct 2021
Publisher:
CDS
Description:
As a part of an extensive program focused on the global properties and evolution of active stars, high-precision UBV(RI)_c_ and UBV photometry of 31 selected stars is presented. The UBV(RI)_c_ observations were collected at the European Southern Observatory over the 31 December 1992-18 January 1993 and the 20 November-3 December 1993 intervals. Additional UBV photometry obtained by the ``Phoenix" and by the Catania Astrophysical Observatory Automatic Photoelectric Telescopes from 1990 to 1993 is also presented for some of the program stars. Significant evolution of the light curves, period variations and evidence for long-term variability of the global degree of spottedness are found. Some spectral classifications are revised and the inferred photometric parallaxes are compared, whenever possible, with the values measured by the Hipparcos satellite (Cat. <I/239>). These observations are finalized to the construction of an extended photometric database, which can give important clues on topics such as the stability of spotted areas, differential rotation, solar-like cycles and the correlation between inhomogeneities at different atmospheric levels.
16189. UBV(RI)c photometry of active stars. X.
ID:
ivo://CDS.VizieR/J/A+A/400/659
Title:
UBV(RI)c photometry of active stars. X.
Short Name:
J/A+A/400/659
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of an extensive program focused on the global properties and evolution of active stars, high-precision UBV(RI)c and UBV photometry of 18 selected stars is presented. UBV(RI)c observations were collected at the European Southern Observatory over the intervals 21-28 September 1994 and 25 November - 05 December 1994. Additional UBV photometry obtained late in 1994 by Catania Astrophysical Observatory Automatic Photoelectric Telescope is also presented. Significant evolution of the light curves, period variations and evidence for long-term variability of the global degree of spottedness are found. Some spectral classifications are revised and photometric parallaxes are compared, whenever possible, with the values measured by the Hipparcos satellite. These observations are finalized to the construction of an extended photometric database, which can give important clues on topics such as the stability of spotted areas, differential stellar rotation, solar-like activity cycles and the correlation between inhomogeneities at different atmospheric levels.
16190. UBV(RI)_c_ photometry of HIP red stars
ID:
ivo://CDS.VizieR/J/MNRAS/334/20
Title:
UBV(RI)_c_ photometry of HIP red stars
Short Name:
J/MNRAS/334/20
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present homogeneous and standardized UBV(RI)_c_ photometry for nearly 550 M stars selected from the Hipparcos satellite data base (Cat. <I/239>) using the following selection criteria: lack of obvious variability (no Hipparcos variability flag); {delta}<+10{deg}, (V-I)>1.7; and V magnitude fainter than about 7.6. Comparisons are made between the current photometry, other ground-based data sets and Hipparcos photometry. We use linear discriminant analysis to determine a luminosity segregation criterion for late-type stars, and principal component analysis to study the statistical structure of the colour indices and to calibrate absolute magnitude in terms of (V-I) for the dwarf stars. Various methods are used to determine the mean absolute magnitude of the giant stars. We find 10 dwarf stars, apparently previously unrecognized (prior to Hipparcos) as being within 25pc, including five within 20pc.

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