INFRARED APERTURE PHOTOMETRY AT ESO (1983-1994) AND ITS FUTURE USE

We describe the infrared (IR) photometric system for the single channe l photometers at ESO, which have been used from 1983 until 1994. In ad dition to the broadband near infrared (NIR, 1-5 mu m) photometric syst em presented in 1991 by Bouchet et al. and Bersanelli et al., we descr ibe a narrow-band NIR photometric system and a mid infrared (MIR, 7-20 mu m) photometric system. We also extend the set of NIR standard star s by Bouchet et al. towards fainter objects (K similar or equal to 9). The photometric data of the standard stars in these systems were extr acted from the complete IR photometric data archive of ESO, covering 1 0 years. The zeropoints of the NIR photometry are set by assuming that HR 3314 has a V-magnitude of 3.89, and that V-K=-0.05, J-K=-0.01, H-K =-0.01, K-L'=0.00, K-M=0.00. The zeropoints of the MIR photometry are set by assuming that the colours of beta Hyi (HR 0098) and alpha CenA (HR 5459) are equal to the colours of the Sun. We adopt the absolute c alibration of Megessier (1995) for the NIR and we argue that this cali bration can be extrapolated to 20 mu m, using the MIR calibrations by Rieke et al. (1985) and Cohen et al. (1992). The definition of the zer opoints is consistent with the absolute calibration. We obtained accur ate (sigma similar or equal to 0.02 mag.) NIR photometry of about 240 standard stars and MIR photometry of about 40 standard stars (sigma si milar or equal to 0.04 mag). Comparison of our NIR photometric system with other well established systems shows that there are some small co lour dependencies and zeropoint offsets which are always smaller than about 0.02 mag. except for the L' band.