No abstract

The blazar 3C 279, one of the brightest identified extragalactic objects in the γ-ray sky, underwent a large (factor of ∼10 in amplitude) flare in γ-rays towards the end of a 3-week pointing by CGRO, in 1996 January-February. The flare peak represents the highest γ-ray intensity ever recorded for this object. During the high state, extremely rapid γ-ray variability was seen, including an increase of a factor of 2.6 in ∼8 hr, which strengthens the case for relativistic beaming. Coordinated multifrequency observations were carried out with RXTE, ASCA, ROSAT and IUE and from many ground-based observatories, covering most accessible wavelengths. The well-sampled, simultaneous RXTE light curve shows an outburst of lower amplitude (factor of ≃3) well correlated with the γ-ray flare without any lag larger than the temporal resolution of ∼1 day. The optical-UV light curves, which are not well sampled during the high energy flare, exhibit more modest variations (factor of ∼2) and a lower degree of correlation. The flux at millimetric wavelengths was near an historical maximum during the γ-ray flare peak and there is a suggestion of a correlated decay. We present simultaneous spectral energy distributions of 3C 279 prior to and near to the flare peak. The γ-rays vary by more than the square of the observed IR-optical Stanford, CA 94305

BL Lacertae was detected by the EGRET instrument on the Compton Gamma Ray Observatory at the 10.2 j level with an average flux of photons cm Ϫ2 s Ϫ1 , at energies greater than 100 MeV, during Ϫ8(171 ‫ע‬ 42) # 10 the optical outburst of 1997 July. This flux is more than 4 times the previously highest level. Within the July 15-22 observation there was a dramatic factor of 2.5 increase in the gamma-ray flux on July 18.75-19.08, apparently preceding, by several hours, a brief optical flare. The gamma-ray flux decreased to its previous level within 8 hr, and the optical flux decreased to its prior level in less than 2 hr. The gamma-ray photon spectral index of indicates that the spectrum during the 7 day observation was harder than the previous 1.68 ‫ע‬ 0.12 detection.

No abstract

The long-term optical light curves of many active galactic nuclei (AGN) display smooth, cyclic changes in level on time scales of years. Earlier work by Smith et al. (AJ, 105, 437, 1993) estimated the time scales of this previously undiscussed phenomenon for a sample of 60 classical radio-loud quasars. The present study extends the analysis to three additional groups of AGN: the BL Lacertids, the compact galaxies, and the radio-quiet quasars. The average time scale of the BL Lacertids is approximately equal to that of the classical quasars, lending credence to unified models of these objects. The long-term fluctuations of the compact galaxies and the radio-quiet quasars are slower. Our analysis tends to support the division of the BL Lacertids into two populations.