We perform a study of the structure, density, and distribution of ionized circumstellar gas in the strongly interacting binary SX Cas. We apply our new model codes for electron scattering in circumstellar matter to analyze a previously unpublished, extensive linear polarization data set for SX Cas, collected during four successive observing periods in 1981-84 at the Crimean Astrophysical Observatory. These data are complemented by our polarization observations carried out in 2000 and 2005 with the KVA-60 telescope at La Palma.
We present (UBVRI) multicolor linear polarimetric data for 31 of the brightest stars in the area of the open cluster NGC 5749 considered to study the properties of the interstellar medium (ISM) towards the cluster.
We present polarimetric observations in the UBVRI bands corresponding to 54 stars located in the direction of NGC 5606. Our intention is to analyze the dust characteristics between the Sun and the cluster, as well as to confirm doubtful memberships using polarimetric tools. We also want to determine if a group of 11 B and A stars identified in the past by Vazquez & Feinstein (1991A&AS...87..383V) in front of NGC 5606 has any physical entity. From polarimetric data we have found at least two dust layers along the line of sight to the open cluster.
We present (UBVRI) multicolor linear polarimetric data for 26 of the brightest stars in the area of the open cluster Stock 16 that were considered to study the properties of the ISM (interstellar medium) towards the cluster. Our data yield a mean polarization percentage of P~2.5%, close to the polarization value produced by the ISM with normal efficiency (P_{lambda}_max_~5E_B-V_) undergoing a color excess of E_B-V_=0.51. The mean angle of the polarization vectors, {theta}=74.9deg, agrees quite well with the expected angle produced by dust particles aligned in the direction of the galactic disk (and the magnetic field) in the region. A study of the extinction suffered by the stars in the zone was also performed combining our new data with previous photometric data. In this sense, our analysis indicates that the visual absorption affecting Stock 16 stars is mainly produced in front of the cluster by a dust cloud at approximately 500 pc from the sun. The large polarization value of the non-member star, WR 51, confirms its background star nature.
UBVRI photoelectric sequences for three low-latitude galactic globular clusters. NGC 5286, NGC 5927, and NGC 6541, are presented herein. All include fields suitable for CCD coverage. The number of stars and the range of magnitudes and colors are: * NGC 5286: 8 stars 13.6<V<15.3, 0.6<B-V<1.3 (table2) * NGC 5927: 11 stars 11.3<V<14.9, 0.3<B-V<1.6 (table3) * NGC 6541: 16 stars 12.2<V<15.7, 0.2<B-V<1.6 (table4) The stars were measured an average of seven times on at least five different nights. To the best of our knowledge, none of these stars have UBVRI photoelectric measurements reported by other authors.
The catalog contains UBVRI photoelectric observations of 223 stars, mostly in an approximately 2-degree zone centered on the celestial equator. The catalog is intended to provide a uniform set of new standards, available to various sizes of telescopes in both hemispheres, on an internally consistent, homogeneous system. Most of the stars are in Selected Areas 92-115 and fall in the magnitude range of about 7 to 12.5 in V and color range -0.3 to +2.0 in B-V. The data include equatorial coordinates, photoelectric magnitudes and colors, numbers of observations, and computed internal errors. See the complete description by Wayne H. Warren Jr., either in plain ascii (file adc.doc) or in LaTeX format (file adc.tex)
New broadband UBVRI photoelectric observations on the Johnson-Kron-Cousins photometric system have been made of 202 stars around the sky, and centered at the celestial equator. These stars constitute both an update of and additions to a previously published list of equatorial photometric standard stars. The list is capable of providing, for both celestial hemispheres, an internally consistent homogeneous broadband standard photometric system around the sky. When these new measurements are included with those previously published by Landolt (1992, Cat. II/183), the entire list of standard stars in this paper encompasses the magnitude range 8.90<V<16.30, and the color index range -0.35<(B-V)<+2.30.
UBVRI photoelectric observations have been made of 109 stars around the sky, centered more or less at -50{deg} declination. The majority of the stars fall in the magnitude range 10.4<V<15.5 and in the color index range -0.33<(B-V)<+1.66. These new broadband photometric standard stars average 16.4 measurements each from data taken on 116 different nights over a period of 4yr. Similar data are tabulated for 19 stars of interest that were not observed often enough to make them well-defined standard stars.
High-quality CCD-based UBVRI photometry is presented for ~45000 stars distributed among 60 different fields centered on the celestial equator and at {delta}{approx}-50{deg}. This photometry has been calibrated to the standard Johnson UBV and Kron-Cousins RI systems via observations of the UBVRI standard stars presented in the works of Landolt. The majority of the stars in our photometric catalog fall in the magnitude range 12<~V<~22 and in the color range -0.3<~(B-V)<~1.8. Each star averages 67 measures in each UBVRI filter from data taken on 250 different photometric nights over a period of ~6.5yr from two different telescopes. Our final photometric database effectively extends the UBVRI standard star network defined by Landolt to much fainter magnitudes and increases the number density of stars within pre-existing standard fields. Hence, these new, fainter standards serve as suitable calibrators for investigators who employ either small or large-aperture telescopes for their observational projects.
