Near-infrared photometry of blazars

The rapid variability of blazars in almost all wavelengths is now well esta blished. Two days of observations were conducted at the Palomar Observatory during the nights of 25 and 26February 1997 with the 5-meter Hale telescop e, in order to search for rapid variability in the near-infrared (NIR) band s J, H, K-s for a selection of eight blazars. With the possible exception o f 1156+295 (4C 29.45), no intraday or day-to-day variability was observed d uring these two nights. However, for these eight blazars, we have measured the NIR VFnu luminosities and spectral indices. II has recently been report ed that the gamma-ray emission is better correlated with the near-infrared luminosity than with the X-ray luminosity (Xie et al. 1997). This correlati on is suggested as a general property of blazars because hot dust is the ma in source of soft photons which are scattered off the relativistic jets of electrons to produce the gamma rays by inverse Compton scattering. We thus used this relationship to estimate the gamma-ray luminosity.