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UBVRI Photometric Standard Stars Around the Celestial Equator: Updates and Additions
New broadband UBVRI photoelectric observations on theJohnson-Kron-Cousins photometric system have been made of 202 starsaround the sky, and centered at the celestial equator. These starsconstitute both an update of and additions to a previously publishedlist of equatorial photometric standard stars. The list is capable ofproviding, for both celestial hemispheres, an internally consistenthomogeneous broadband standard photometric system around the sky. Whenthese new measurements are included with those previously published byLandolt (1992), the entire list of standard stars in this paperencompasses the magnitude range 8.90 < V < 16.30, and the colorindex range -0.35 < (B - V) < +2.30.
| The Calibration of the Swift UVOT Optical Observations: A Recipe for Photometry
The Ultraviolet/Optical Telescope (UVOT) on board Swift has thecapability to provide critical insight into the physics of the earlyafterglows of gamma-ray bursts (GRBs). But without precise calibrationof the UVOT to standard photometric systems, it is impossible toleverage late-time, ground-based follow-up data to the early-time UVOTobservations. In this paper, we present a calibration of the Swift UVOTphotometry to the standard Johnson UBV system for the UVOT U, B, and Vfilters, and a step-by-step photometry recipe for analyzing these data.We base our analysis on aperture photometry performed on theground-based and UVOT observations of the local standard stars in thefields of supernovae (SNe) 2005am and 2005cf and a number of Landoltstandard stars. We find that the optimal photometry aperture radius forUVOT data is small (2.5" for unbinned data, 3.0" for 2×2 binneddata), and we show that the coincidence-loss (C-loss) correction isimportant even for relatively faint magnitudes (16-19 mag). Based on atheoretically motivated model, we fit the C-loss correction with twoparameters, the photometric zero point (ZP) and the saturation magnitude(m&infy;), and derive tight constraints for both parameters[σ(ZP)=0.01 mag and σ(m&infy;)=0.02 mag)]. Wefind that the color-term correction is not necessary for the UVOT B andV filters but that it is necessary for the U filter for blue objects[(U-V)<0.4 mag]. We analyze the UVOT UBV photometry of SN 2005am andfind that the UVOT photometry is generally consistent with theground-based observations but that a difference of up to 0.5 mag isfound when the SN became faint. We also apply our calibration results tothe UVOT observations of GRB 050603. There is a scatter of ~0.04-0.08mag in our final UVOT photometry, the cause of which is unclear, but itmay be partly due to the spatial variation in the pixel sensitivity ofthe UVOT detector.
| Absolute magnitudes for late-type dwarf stars for Sloan photometry
We present a new formula for absolute magnitude determination forlate-type dwarf stars as a function of (g-r) and (r-i) for Sloanphotometry. The absolute magnitudes estimated by this approach arebrighter than those estimated by colour-magnitude diagrams, and theyreduce the luminosity function rather close to the luminosity functionof Hipparcos.
| 15 colour photometry of the Landolt SA95 standard star field
In this paper, we present a set of photometric observations in 15 colorsof stars in the Landolt SA95 field with the BATC system. The wavelengthscovered by the system range from 300 nm to 1000 nm. Visual magnitudes ofthe stars studied in the field are from the 10th to 20th mag. Theobservational methodology and the data reduction procedures aredescribed. The relationships between the BATC intermediate-band systemand the Landolt UBVRI broad band system are obtained. A catalogue of thephotometry has been produced which contains the SEDs of 3613 stars. Thework is partly supported by Chinese National Sciences Foundation underthe contract No. 19833020 and No. 19503003. The catalogue is onlyavailable at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/361
| Photometric catalog of nearby globular clusters. I. A large homogeneous (V,I) color-magnitude diagram data-base
We present the first part of the first large and homogeneous CCDcolor-magnitude diagram (CMD) data base, comprising 52 nearby Galacticglobular clusters (GGC) imaged in the V and I bands using only twotelescopes (one for each hemisphere). The observed clusters represent75% of the known Galactic globulars with (m-M)_V<= 16.15 mag, covermost of the globular cluster metallicity range (-2.2 <= [Fe/H]<=-0.4), and span Galactocentric distances from ~ 1.2 to ~ 18.5 kpc. Inthis paper, the CMDs for the 39 GGCs observed in the southern hemisphereare presented. The remaining 13 northern hemisphere clusters of thecatalog are presented in a companion paper. For four clusters (NGC 4833,NGC 5986, NGC 6543, and NGC 6638) we present for the first time a CMDfrom CCD data. The typical CMD span from the 22nd V magnitudeto the tip of the red giant branch. Based on a large number of standardstars, the absolute photometric calibration is reliable to the ~ 0.02mag level in both filters. This catalog, because of its homogeneity, isexpected to represent a useful data base for the measurement of the mainabsolute and relative parameters characterizing the CMD of GGCs. Basedon data collected at the European Southern Observatory, La Silla, Chile.
| 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.
| Photoelectric UBV photometry of stars in ten Selected Areas
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973MNRAS.164..121P&db_key=AST
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