J/AcA/50/421ivo://CDS.VizieR/J/AcA/50/421doi:10.26093/cds/vizier.120500421CDSWozniak P.R.2025-09-25T20:14:41Z2008-01-20T07:34:39ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgravitational-lensingphotometryWe present an implementation of the difference image photometry based on the Alard and Lupton optimal PSF matching algorithm. The most important feature distinguishing this method from the ones using Fourier divisions is that equations are solved in real space and the knowledge of each PSF is not required for determination of the convolution kernel. We evaluate the method and software on 380G B of OGLE-II bulge microlensing data obtained in 1997-1999 observing seasons. The error distribution is Gaussian to better than 99% with the amplitude only 17% above the photon noise limit for faint stars. Over the entire range of the observed magnitudes the resulting scatter is improved by a factor of 2-3 compared to DoPhot photometry, currently a standard tool for massive stellar photometry in microlensing searches. For testing purposes the photometry of approx 4600 candidate variable stars and sample difference image data are provided for BUL_SC1 field. In the candidate selection process, very few assumptions have been made about the specific types of flux variations, which makes this data set well suited for general variability studies, including the development of the classification schemes.2000AcA....50..421Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AcA/50/421CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/AcA/51/175 : OGLE-II DIA microlensing events (Wozniak+, 2001)http://astro.Princeton.EDU/~wozniak/dia/bul_sc1 : All datahttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AcA/50/421https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AcA/50/421http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AcA/50/421https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AcA/50/421https://vizier.iucaa.in/viz-bin/votable?-source=J/AcA/50/421http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AcA/50/421GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AcA/50/421/catalog*The Bulge-SC1 catalog of candidate variables detected on difference framesPFluxFlux-profile photometryphot.flux.density;em.optdoubleBackgBackgroundinstr.backgroundfloatSeqStar sequential number (OGLE BUL-SC1 NNNN)meta.recordintprimaryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintXposX template coordinate (1)pixpos.cartesian.x;instr.detfloatYposY template coordinate (1)pixpos.cartesian.y;instr.detfloate_PFluxerror in Flux-profile photometrystat.errorfloatAFluxFlux-aperture photometryphot.flux.density;em.optdoublee_AFluxerror in Flux-aperture photometrystat.errorfloatchi2chi2 per pixel of the PSF fit (usually a bad fit due to local crowding)stat.fit.chi2doubleCorrCorrelation coefficient with the PSFstat.fit.paramfloatbadNumber of bad pixels within the fitting radius (3.0 pix)meta.numberintVarVariability type (2)meta.noteintNfrNumber of frames used in centroid calculationmeta.numberintFlag[0/1] Crowding flag (0 - uncrowded)meta.code.errorintrFluxRough estimate of the reference flux from DIA catalogphot.flux.density;em.optdoubleDistDistance between the variable and the closest DoPhot starpixpos.angDistancefloatmag? DoPhot magnitude of the closest matchmagphot.magfloatnullableArFlux? Accurate reference flux (converted from DoPhot mag)phot.flux.density;em.optdoublenullablemag0Magnitude zero point for that star (same for all variables in each subframe)phot.mag;arith.zpfloat