Abstract

The VLT Spectrometer and Imager for the Mid-Infrared (VISIR) is a Paranal instrument dedicated to observations through the two mid-infrared (MIR) atmospheric windows: N band (8-13 ?m) and Q band (16.5-24.5 ?m). As part of standard operations, VISIR has been continuously observing MIR standard stars for more than a year. The derived conversion factors, sensitivities, etc. have been systematically collected in the database, allowing for statistical analysis of their temporal behavior. We analyzed long time variations of the conversion factor of selected VISIR standard stars and found that they show variability of less than 10% in the N band and less than 20% in the Q band. © 2008 Springer-Verlag Berlin Heidelberg.