Search

Performing a systematic search in the BeppoSAX archive for high energy (15–100 keV) serendipitous sources at high galactic latitudes (|b| ⩾ 13°), we defined a sample of 12 regions in which the PDS/MECS cross-calibration constant, resulting from the fit of the target source with a simple power law, is substantially higher than the nominal value of 0.75–0.95 estimated from instrument intercalibration. This is probably due to the presence of a serendipitous source in the PDS field of view which is contaminating the PDS spectrum of the pointed source. This approach allowed us to find new six hard X-ray emitting sources (PKS 2356-611, 2MASX J14585116-1652223, NGC 1566, NGC 7319, PKS 0101-649 and ESO 025-G002), which are the object of this work. In two fields, the likely candidate contaminating sources are present in the MECS field of view; for these sources we have performed a broad band (1.5–100 keV) spectral analysis. In the remaining four cases, the identification of the source likely to provide the emission detected by the PDS is based on the search in high energy catalogs.

The Seyfert 1 galaxy MCG-6-30-15 (z≃0.008, L B ∼4×10 44 erg/s) was observed by XMM-Newton on 2000 June 11-12, for a total of 95 ks. The source shows high flux and spectral variability down to timescales of t ∼300 s. This work presents the results of the time-resolved spectral analysis of the brightest flare (a factor of 2 variation in ∼1000 s) which occurred during the observation. The analysis of such flare indicates: 1) a softening of the X-ray spectrum in phase with the flux, and 2) a soft-to-hard time lag of about ∼ 600 s. A strong and complex Fe-Kαemission feature is detected ∼ 3000 s after the flare. The same feature was not present before and during the flare. This may indicate that the Fe line was produced as a consequence of the flare. The present analysis allows the formulation of a different hypothesis for the physical mechanisms responsible for the X-ray emission.