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E. Massaro

Publications and source records attributed to E. Massaro.

75 records · Page 5Linked to original sources

Reprocessing and Variable Cold Absorption in the Broad-Line Radio Galaxy 3C390.3

A BeppoSAX observation of the BLRG 3C390.3 is reported. For the first time, both the 6.4 keV iron line and a strong reflection hump, produced by the illumination of the primary X-ray emission on cold matter, are detected in this source. The 0.1-100 keV continuum is modeled by an absorbed power law (Γ~ 1.8) reflected at high energies by material with a fairly large covering factor (Ω/2π~1). The iron line is intrinsically narrow ($σ=73(+207,-73) eV) and has an equivalent width of ~140$ eV. We discuss the results in the context of current models for AGNs and suggest that the primary X-ray power law continuum is probably produced by a hot inner flow, while the reprocessed radiation comes from an outer cold thin disk, and/or from a thick torus at even larger radii. Further observations with BeppoSAX could distinguish between the latter two cases. Beamed radiation associated to the radio jet is unlikely to contribute significantly to the X-ray emission. Finally, an historical study of the column density NH, also reported here, shows that the absorption along the line of sight changes in time. The NH time variability, which is not correlated with that of the primary continuum, seems to imply variations of the geometry of the absorber rather than variations in the ionization state of the gas.

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BeppoSAX observations of PKS 0528+134

We report on the BeppoSAX observations of the gamma-ray blazar PKS 0528+134 performed in Feb and Mar 1997, during a multiwavelength campaign involving EGRET and ground based telescopes. The source was in a faint and hard state, with energy spectral index alpha=0.48+-0.04 between 0.1 and 10 keV, and [2-10] keV flux of 2.7E-12 erg/cm2/s. No significant variability was observed. The source was detected in the 20-120 keV band by the PDS, with a flux lying slightly above the extrapolation from lower X-ray energies. Comparing this low state with previous higher states of the source, there is an indication that the X-ray spectrum hardens and the gamma-ray spectrum steepens when the source is fainter.

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Optical-IUE observations of the gamma-ray loud BL Lacertae object S5 0716+714: data and interpretation

We monitored the BL Lac object S5 0716+714 in the optical band during the period November 1994-April 1995, which includes the time of a gamma-ray observation by the Energetic Gamma Ray Experiment Telescope (EGRET) on February 14--28, 1995. The light curves in the R and B bands show fast fluctuations superimposed on longer timescale variations. The color index correlates with intensity during the rapid flares (the spectrum is flatter when the flux is higher), but it is rather insensitive to the long term trends. Over the 5 month observational period the light curve shows an overall brightening of about 1 mag followed by a fast decline. The EGRET pointing covers part of the very bright phase (V about 13.2) and the initial decline. An ultraviolet spectrum was also obtained with the International Ultraviolet Explorer (IUE) (1200-3000 A) during the EGRET observations. The variability of the optical emission of S5 0716+714 by itself sets important constraints on the magnetic field strength and on the physical processes responsible for it. Interpreting the whole electromagnetic spectrum with synchrotron self Compton models leads to the prediction of a bright gamma-ray state during the EGRET pointing. We discuss how the gamma-ray data could be used as a diagnostic of the proposed models.

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