Variability of Seyfert galaxies in the near-infrared — II. The unusual starburst Seyfert NGC 7469

The bright Seyfert 1 and starburst galaxy NGC 7469 has been monitored at JHKL for 13 yr. Its variations have been small, amounting to less than 0.3 mag, except for an event in 1989 when the flux from its active nucleus declined to about one quarter of its normal level.   Using the technique of flux variation gradients (FVGs), the variations have been analysed, taking into account the known JHK fluxes from the star-forming ring surrounding the nucleus. By comparing the FVGs of NGC 7469 with those of other Seyfert galaxies, the nucleus of NGC 7469 is found to suffer very little reddening.   The active nucleus normally contributes more than 50 per cent of the flux measured in the K and L bands through an aperture of 12 arcsec diameter.   Infrared excesses (above the fluxes expected from stars) are observed from the circumnuclear ring at both K and L and it is suggested that they arise from warm, small particles that also emit the aromatic hydrocarbon features seen in this galaxy.