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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2004 UBVR Photometry of the Eclipsing Binary KR Cyg
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A test of arm-induced star formation in spiral galaxies from near-infrared and Hα imaging
We have imaged a sample of 20 spiral galaxies in Hα and in thenear-infrared K band (2.2 μm), in order to determine the location andstrength of star formation in these objects with respect toperturbations in the old stellar population. We have found that starformation rates are significantly enhanced in the vicinity of K-bandarms. We have also found that this enhancement in star formation rate inarm regions correlates well with a quantity that measures the relativestrengths of shocks in arms. Assuming that the K-band light is dominatedby emission from the old stellar population, this shows that densitywaves trigger star formation in the vicinity of spiral arms.
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The Distance to the Large Magellanic Cloud via the Eclipsing Binary HV 2274
We present UBV photometry of the eclipsing binary Harvard Variable 2274in the Large Magellanic Cloud (LMC). The stellar parameters of thisbinary system were recently calculated by Guinan et al., who gave both areddening toward HV 2274 of E(B-V)=0.083+/-0.006 and a distance modulusto the LMC of μLMC=18.42+/-0.07. The reddening of thissystem was also determined by Udalski et al., who foundE(B-V)=0.149+/-0.015. With Udalski et al. B and V photometry, Guinan etal. obtained E(B-V)=0.12+/-0.009 and μLMC=18.30+/-0.07.Using our UBV photometry, we derive a reddening of E(B-V)=0.088+/-0.023,consistent with the original value of Guinan et al. and supporting alonger distance modulus to the LMC of aboutμLMC=18.40+/-0.07. We stress the uncertainties inherent inground-based UBV photometry and the concomitant uncertainties indetermining distances based upon such photometry.
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GSC 2137:3085 - A Suspected New Variable
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The photometric transformation of CCD camera on the BAO 2.16m telescope.
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UBVRI photometric standard stars in the magnitude range 11.5-16.0 around the celestial equator
UBVRI photoelectric observations have been made on theJohnson-Kron-Cousins photometric system of 526 stars centered on thecelestial equator. The program stars within a 298 number subset havesufficient measures so that they are capable of providing, fortelescopes of intermediate and large size in both hemispheres, aninternally consistent homogeneous broadband standard photometric systemaround the sky. The stars average 29 measures each on 19 nights. Themajority of the stars in this paper fall in the magnitude range11.5-16.0, and in the color range -0.3 to +2.3.
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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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The 77-81 intermediate-band photometric system
The 77-81 intermediate-band photometric color system for the study oflate-type stars is defined. The passbands are centered on a region ofTiO absorption at 7750 A (77) and on a region of CN absorption at 8100 A(81). Good agreement is found between measurements made on the 77-81system with different detectors. The 77-81 color is well correlated withM type and reasonably correlated with carbon-richness class. The 77-81,V-I color-color diagram clearly distinguishes M and C types from otherstars. It is also shown that the 77-81 color may be used to measure TiOband strength.
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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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Distances to eclipsing binaries. III - Masses, radii, and absolute magnitudes of 96 stars
Distances to, and absolute magnitudes of, 96 components of eclipsingbinaries with well-determined absolute dimensions have been computedusing V-R photometry. The calculations take into account interstellarreddening, which is estimated from existing UBV and uvby-betaphotometry, as well as photometric proximity effects. The resultingabsolute magnitudes, dimensions, and masses are compared with zero-agemain sequences predicted by theory. Theory is in good agreement with theobserved data for stars more massive than the sun if a composition (X,Y, Z) = (0.66 + or - 0.03, 0.303 + or - 0.03, 0.037 + or - 0.005) ischosen. The corresponding helium-to-hydrogen number ratio is 0.115 + or- 0.02, in agreement with previous estimates.
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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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