Of the blazars detected by EGRET in GeV γ rays, 3C 279 is not only the best-observed by EGRET, but also one of the best-monitored at lower frequencies. We have assembled eleven spectra, from GHz radio through GeV γ rays, from the time intervals of EGRET observations. Although some of the data have appeared in previous publications, most are new, including data taken during the high states in early 1999 and early 2000. All of the spectra show substantial γ-ray contribution to the total luminosity of the object; in a high state, the γ-ray luminosity dominates over that at all other frequencies by a factor of more than 10. There is no clear pattern of time correlation; different bands do not always rise and fall together, even in the optical, X-ray, and γ-ray bands.The spectra are modeled using a leptonic jet, with combined synchrotron self-Compton + external Compton γ-ray production. Spectral variability of 3C 279 is consistent with variations of the bulk Lorentz factor of the jet, accompanied by changes in the spectral shape of the electron distribution. Our modeling results are consistent with the UV spectrum of 3C 279 being dominated by accretion disk radiation during times of low γ-ray intensity.Subject headings: quasars: individual (3C 279)

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Abstract. -The Far Infrared (FIR) properties of galaxies which are members of compact groups bear relevant information on the dynamical status and the physical properties of these structures. All studies published so far have been undermined by the poor sensitivity and spatial resolution of the IRAS-PSC and IRAS Sky Survey data. We used the HIRAS software available at the IRAS server at the Laboratory for Space Research in Groningen to fully exploit the redundancy of the IRAS data and to approach the theoretical diffraction limit of IRAS. Among the 97 groups which were observed by IRAS, 62 were detected in at least one band, while reliable upper limits were derived for all the others. Among the detected groups, 49 were fully or partially resolved, i.e. it was possible to discriminate which member or members emit most of the FIR light. At 60 µm, for instance, 87 individual sources were detected in 62 groups. In order to ease the comparison with data obtained at other wavelengths -and in particular in the X and radio domains -we give co-added and HIRAS maps for all the detected groups.

Abstract. Based on film copies of the POSS-II we inspected a wide area of ∼ 6000• in the direction of the nearest cosmic void:As a result we present a list of 78 nearby dwarf galaxy candidates which have angular diameters > ∼ 0. 5 and a mean surface brightness < ∼ 26 mag/ . Of them 22 are in the direction of the Local Void region. To measure their redshifts, a HI survey of these objects is undertaken on the 100 m Effelsberg telescope.

Abstract. We present here results of studies of the properties of galaxies located in very low density environments. We observed 26 blue compact galaxies (BCGs) from the Second Byurakan (SBS) and Case surveys located in voids with the radial velocities V hel . 11 000 km s −1 , two BCGs in the void behind the Virgo cluster and 11 BCGs in denser environments. H i fluxes and profile widths, as well as estimates of total H i masses, are presented for the 27 detected galaxies (of which 6 are in three galaxy pairs and are not resolved by the radiotelescope beam). Preliminary comparisons of void BCGs with similar objects from intermediate density regions -in the general field and the Local Supercluster (sub-samples of BCGs in the SBS zone) and in the dense environment of the Virgo Cluster (a BCD sample) -are performed using the hydrogen-to-blue-luminosity ratio M (H i)/LB. We find that for the same blue luminosity, for MB > −18. m 0, BCGs in lower density environment have on average more H i. The slope β of the M (H i)/LB _ L β for BCGs shows a trend of steepening with decreasing bright galaxy density, being very close to zero for the densest environment considered here and reaching β = −0.4 for voids.