Calibration of the MACHO Photometry Database
نویسندگان
چکیده
The MACHO Project is a microlensing survey that monitors the brightnesses of ∼60 million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Galactic bulge. Our database presently contains about 80 billion photometric measurements, a significant fraction of all astronomical photometry. We describe the calibration of MACHO two-color photometry and transformation to the standard Kron-Cousins V and R system. Calibrated MACHO photometry may be properly compared with all other observations on the Kron-Cousins standard system, enhancing the astrophysical value of these data. For ∼9 million stars in the LMC bar, independent photometric measurements of ∼20,000 stars with V < ∼ 18 mag in field-overlap regions demonstrate an internal precision σV = 0.021, σR = 0.019, σV −R = 0.028 mag. The accuracy of the zero-point in this calibration is estimated to be ±0.035 mag for stars with colors in the range −0.1 < (V − R) < 1.2 mag. A comparison of calibrated MACHO photometry with published photometric sequences and new Hubble Space Telescope observations shows agreement. The current calibration zero-point uncertainty for the remainder of the MACHO photometry database is estimated to be ±0.10 mag in V or R and ±0.04 mag in (V − R). We describe the first application of calibrated MACHO photometry data: the construction of a color-magnitude diagram used to calculate our experimental sensitivity to detect microlensing in the LMC. Subject headings: astronomical databases: surveys – astronomical methods: data analysis – astronomical techniques: photometric
منابع مشابه
ar X iv : a st ro - p h / 99 09 22 7 v 1 1 4 Se p 19 99 Calibration of the MACHO Photometry Database
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