Calibration of the UBVRI high-speed photometer of Laboratorio Nacionale de Astrofisica, Brazil

Abstract

We describe the characteristics and performance of a high-speed multicolor photometer, FOTRAP, which has been used since 1988 at LNA, Laboratorio Nacional de Astrofisica/CNPq, Brazil. The optomechanical concepts, electronics, and software are outlined. We discuss the quality and consistency of the transformations from the natural system to the UBVRI standard system. We give particular attention to the problem of transforming to the standard system observations of objects with blue spectra, like cataclysmic variables. We compare the results of our UBVRI measurements for a few spectrophotometric standards with the values published in the literature.

Photometric variability of southern T Tauri stars

“…Photoelectric differential photometry in UBV (RI) C were also taken with the same telescopes using the FOTRAP (Jablonski et al 1994). This sample includes recently identified TTS sorted by their IRAS colors and conspicuous Li lines (Pico dos Dias Survey -henceforth PDS; Gregorio-Hetem et al 1992, henceforth GHETAL92).…”

Identification of DQ Serpentis and DT Serpentis as symbiotic stars

“…7 to 11) take into account the errors due to photon noise in the measurements and errors associated with the transformation to the standard system. A more complete description of the procedures of reduction, as well of the FOTRAP photometer and the photometric system, can be found in Jablonski et al (1994).…”

Southern and equatorial irregular variables

“…For a few nights in which we did not have calibration sequences we used transformation coefficients determined in the same mission being, in most cases, calibrations from previous or subsequent nights. The procedures that we used for the reduction of the data are those described in Jablonski et al (1994). This reference also contain a detailed description of the FOTRAP photometer and the photometric system.…”