A mid-to far-infrared variability study of eight active galactic nuclei.

The authors present a mid- to far-infrared variability study of a heterogeneous sample of active galactic nuclei (AGN) using data from the Infrared Astronomical Satellite (IRAS). The data have been taken from the IRAS Additional Observation archives. The source list comprises eight AGN; one Seyfert type 2 galaxy (NGC 1275), three Seyfert type 1 galaxies (NGC 4151, III Zw 2 and AKN 374), two quasars (PG 1351+64 and 1156+295) and two BL Lacertae objects (OJ 287 and MKN 501). The observations cover a variety of time-scales from days to months. In only one case, that of the BL Lac object OJ 287, was significant evidence found for variability within the IRAS waveband, although the OVV quasar 1156+295 shows evidence for variability by comparison with archival ground-based data.