Long-term infrared variation of 3C 279 and 4C 29.45

Abstract

In this paper, the historical infrared (JHK) data compiled from 22 publications are presented for 3C279 and 4C29.45. Relation between color index and magnitude and between color-color indices are discussed. (J-K) is found closely correlated with (J-H) while (J-H) is almost not correlated with (H-K), which is perhaps due to two facts of (1) (J-K) shows wider distribution than (J-H) and (H-K) and (2) the spectrum deviates from the power law. For color-magnitude relation, there is a correlation of color index increasing with magnitude for 3C279 suggesting that the spectrum flattens when the source brightens. But an opposite tendency is also noted between (H-K) and J when I is fainter than 14 magnitude, which suggests that the near-IR spectrum of 3C279 consists of, at least, two components. No similar result is found for 4C29.45. The largest amplitude infrared variation is smaller than but comparable with the largest amplitude variation for the two objects.