We present a solution to the problem of performing approximate pattern matching on compressed text. The format we choose is the Ziv-Lempel family, speciically the LZ78 and LZW variants. Given a text of length u compressed into length n, and a pattern of length m, we report all the R occurrences of the pattern in the text allowing up to k insertions, deletions and substitutions, in O(mkn + R) ti...

We discuss the results of modelling the TeV γ-ray spectra of two AGNs, Mkn 501 and Mkn 421 that have almost the same redshifts: z = 0.031 and z = 0.034, respectively. The effect of intergalactic γ-ray absorption is treated as an uncertainty in the measurement of the intrinsic spectrum. Although the objects differ, we obtain satisfactory fits for both of them in a synchrotron self-Compton scenar...

Mkn 421 was observed by Chandra twice, on November 5, 1999 as part of the Chandra calibration program, with the ACIS-HETG configuration, and on May 29, 2000 following our Target Of Opportunity request aimed to catch the source in an ultra-high state, with both the ACIS-HETG and the HRC-LETG configurations. In this contribution we present and compare the two Chandra-MEG observations of Mkn 421, ...

We present a solution to the problem of performing approximate pattern matching on compressed text. The format we choose is the Ziv-Lempel family, speciically the LZ78 and LZW variants. Given a text of length u compressed into length n, and a pattern of length m, we report all the R occurrences of the pattern in the text allowing up to k insertions, deletions and substitutions, in O(mkn + R) ti...

In this work we present the observation of the Mkn 463 field performed with the MECS instrument on– board BeppoSAX in the 1.8–10.5 keV band. The Mkn 463 field is an example of an extragalactic field crowded with absorbed X–ray sources: apart from the Seyfert 2 galaxy Mkn 463 and the well known QSO PG 1352+183 (the only object showing no absorption), two other objects are detected with a column ...

The CAT (Cerenkov Array at Thémis) γ-ray detector 1 operates above 250 GeV since Autumn 1996. Its observation program has been largely devoted to the study of blazars. These objects are radio-loud active galactic nuclei (AGN’s) with a relativistic jet which is pointed directly to the observer. The jet emission dominates that of the accretion disk (and of the host galaxy) over a large energy dom...