Multiband photometry towards the inner Galactic bulge: extinction, atmospheric parameters, and metallicities
Context: .We have obtained BVRI photometry for 21 stellar fields locatedin directions towards the central 3.5^circ of the Galaxy. Each field is10× 10 arcmin in size, and a total of 2 × 105stars were measured. Aims: .Previous analyses based on 2 MicronAll Sky Survey (2MASS) data have shown that these directions have arelatively low extinction (AK ≃ 0.25-0.30). Thecombined optical-infrared sample contains about 3.5 ×104 stars. This large dataset provides a more detailedextinction map within these surveyed areas than previously derived. Thelarge number of colour indexes available also yielded estimates ofeffective temperatures and metallicities for the inner bulge stars. Methods: .Extinction and effective temperature were estimated foreach star based on comparing the observed colours to model predictions.The extinction-corrected colour magnitude diagrams indicate the presenceof a broad red giant branch of inner bulge stars detached from thehelium-burning red clump of both bulge and disc stars. The red giantstars belonging to the bulge form a wide sequence mostly due to variablemetallicity. As previously done by other authors, we derived photometricmetallicities by comparing the position of each bulge red giant to a setof templates based on Galactic globular clusters. Results: .Weconfirm the existence of regions with AK < 0.30 in thesefields, as attested by analysis of the stellar colours. The resultingmetallicity distribution function is peaked at [Fe/H] ≃ -0.25 andextends to supersolar values up to [Fe/H] ≃ 0.3. This distributionis similar among the 4 regions, with relatively small field-to-fieldvariations within the central 1kpc. Our results are also in goodagreement with the metallicity distributions from other authors, bothphotometric and spectroscopic. Put together, this result strongly limitsthe existence of an abundance gradient in the inner bulge.
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VRI Light Curves of SS 433: Photometry and Model
We present the results of VRI CCD photometric observations of SS 433 andVRI light-curve modelings for SS 433. Observations were carried out inthe fall of 1995 using the 51-cm relfector at Osaka Kyoiku University.Three cycles of the binary phase were covered. The mean magnitudes andcolors during the observational periods were V = 14.0, R = 11.1, I =10.5; V - R = 2.88, V - I = 3.50, R - I = 0.62. On October 17 and 18 astrong flare was observed. Theoretical light curves were also calculatedusing a model in which SS 433 consists of a geometrically thick torusaround a compact star and a companion star filling the Roche lobe. Inthe torus picture VRI light curves were first calculated; forappropriate parameters VRI model light curves well reproduce theobservational profiles. In addition, the extinction was first derivedfrom the magnitude difference between the obervation and the model;AV ~ 6--7, AR ~ 3--4, and AI ~ 3. These values are in goodagreement with those of a previous observation.
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Photometry of Stars in the Field of V345 and V553 Aquilae
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Photometry of Stars in the Field of the Mira XY Aquilae
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Photometry of Stars in the Field of AV Cygni and DV Cygni
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V803 Aquilae: A newborn W Ursae Majoris Siamese twin?
A complete photometric analysis of BVRI photometry of the physicallycompact, eclipsing binary V803 Aquilae is presented. Six mean epochs ofminimum light were determined from observations covering three primaryand three secondary eclipses. A period study covering 54 years ofobservation or nearly 77,000 orbital revolutions reveals three distincteras of constant period with two major period jumps of +0.1 s and -0.3s. The light curves shows that the primary and secondary eclipse depthsare identical in V, and are nearly identical in B, R, and I, indicatingthat the components have nearly the same temperatures. Standardmagnitudes were determined and a reddening estimate was made. Asimultaneous solution of the four light curves was computed using theWilson-Devinney synthetic light-curve code. The solution indicates thatthe system consists of twin approximately K4 stars in shallow contactwith a fill-out of approximately 8%. A mass ratio of 1.000 was computedwith a negligible temperature difference of only 6 K. Thus, based on ourpurely photometric solution, V803 Aql is made up of 'Siamese' (contact)twin components. Theory would indicate that the twins have just recentlycome into contact, and the lack of other equal-mass W Ursae Majorissystems would indicate that it is in a very transient or unusual state.
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Photometric investigation of a very short period W UMa-type binary - Does CE Leonis have a large superluminous area?
A complete photometric analysis of BVRI Johnson-Cousins photometry ofthe high northern latitude galactic variable, CE Leo is presented. Theseobservations were taken at Kitt Peak National Observatory on May 31,1989-June 7, 1989. Three new precise epochs of minimum light weredetermined and a linear and a quadratic ephemeris were computed fromthese and previous data covering 28 years of observation. The lightcurves reveal that the system undergoes a brief 20 min totality in theprimary eclipse, indicating that CE Leo is a W UMa W-type binary. Asystemic velocity of about -40 km/s was determined. Standard magnitudeswere found and a simultaneous solution of the B, V, R, I light curveswas computed using the new Wilson-Devinney synthetic light curve codewhich has the capability of automatically adjusting star spots. Thesolution indicates that the system consists of two early K-type dwarfsin marginal contact with a fill-out factor less than 3 percent. Evidencefor the presence of a large (45 deg radius) superluminous area on thecooler component is given.
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UBV(RI)c photometry of equatorial standard stars - A direct comparison between the northern and southern systems
UBV(RI)c photometry of 212 stars from Landolt's list of equatorialstandards is presented. The observations are tied to the system definedby Cousin's E-region standards. A comparison of the present results withLandolt's reveals reasonably good agreement for (V-R)c and (V-I)c, butmarked systematic differences for (B-V) and (U-B). The UBV systems ofCousins and Landolt are evidently not the same and both probably differfrom Johnson's original system.
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Photoelectric observations of classical cepheids.
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Hard X-ray pulse profile and period evolution of AO535 + 26 and GX 1 + 4 as observed by the Franco-Soviet Signe satellite experiments
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986ApJ...310..773R&db_key=AST
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UBV Photometry of Equatorial Stars
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UBVRI photometric standard stars around the celestial equator
It is pointed out that accurate, internally consistent, and readilyaccessible standard star photometric sequences are necessary for thecalibration of the intensity and color data which astronomers obtain atthe telescope. The photometric results provided in connection with thepresent study represent the first part of an effort which is concernedwith the presentation of UBVRI photoelectric photometric standard starsin the magnitude range from 7 to 17 over as broad a range in color aspossible. All of the photometric observations were made with a 31034type photomultiplier used in a pulse counting mode. Some 15 to 25standard stars chosen from Cousins' lists (1973, 1976) in the E-regionswere observed with an 0.4-m telescope each night along with the programstars. UBVRI standard stars were observed periodically throughout thenight. Observations with a 0.9-m telescope were also conducted. TheUBVRI photoelectric observations take into account 223 stars.
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Spectral classifications for Landolt's celestial equatorial standard stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979AJ.....84..783D&db_key=AST
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Equatorial UBVRI photoelectric sequences
From 1335 BVRI observations of 189 stars in selected areas 92-115,Landolt's (1973) network of faint UBV standards has been extended to RI. Of these stars, 173 have four or more observations. The (U-B) valuesof Landolt are adopted, and a well-observed equatorial faint-starnetwork is presented on the Johnson UBVRI photometric system.
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Multicolor photometry of metallic-line stars. III. A photometric catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974RMxAA...1..175M&db_key=AST
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Catalogue et bibliographie des étoiles A à spectre particulier - Deuxième supplément
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Catalogue et bibliographie des étoiles A à spectre particulier
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INHABITED SKY
