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Titolo:
BEPPOSAX OBSERVATIONS OF UNPRECEDENTED SYNCHROTRON ACTIVITY IN THE BL-LACERTAE OBJECT MARKARIAN-501
Autore:
PIAN E; VACANTI G; TAGLIAFERRI G; GHISELLINI G; MARASCHI L; TREVES A; URRY CM; FIORE F; GIOMMI P; PALAZZI E; CHIAPPETTI L; SAMBRUNA RM;
Indirizzi:
SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR BALTIMORE MD 21218 CNR,IST TECNOL & STUDIO RADIAZ EXTRATERR I-40129 BOLOGNA ITALY EUROPEAN SPACE AGCY,ESTEC,DEPT SPACE SCI,DIV ASTROPHYS NL-2200 AG NOORDWIJK NETHERLANDS OSSERV ASTRON BRERA I-22055 LECCE ITALY OSSERV ASTRON BRERA I-20121 MILAN ITALY UNIV MILAN,DEPT PHYS I-22100 COMO ITALY SAX SDC I-00131 ROME ITALY CNR,IST FIS COSM I-20133 MILAN ITALY NASA,GODDARD SPACE FLIGHT CTR GREENBELT MD 20771
Titolo Testata:
The Astrophysical journal
fascicolo: 1, volume: 492, anno: 1998,
parte:, 2
pagine: 17 - 20
SICI:
0004-637X(1998)492:1<17:BOOUSA>2.0.ZU;2-P
Fonte:
ISI
Lingua:
ENG
Soggetto:
EXTRAGALACTIC RADIO-SOURCES; X-RAY-SPECTRA; BLAZARS; GALAXIES; QUASARS; FLUX;
Keywords:
BL LACERTAE OBJECTS, INDIVIDUAL (MARKARIAN 501); GALAXIES, ACTIVE; GALAXIES, NUCLEI; RADIATION MECHANISMS, NONTHERMAL; X-RAYS, GALAXIES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
32
Recensione:
Indirizzi per estratti:
Citazione:
E. Pian et al., "BEPPOSAX OBSERVATIONS OF UNPRECEDENTED SYNCHROTRON ACTIVITY IN THE BL-LACERTAE OBJECT MARKARIAN-501", The Astrophysical journal, 492(1), 1998, pp. 17-20

Abstract

The BL Lacertae object Markarian 501, one of only three extragalacticsources (with Mrk 421 and IES 2344+514) so far detected at TeV energies, was observed with the BeppoSAX satellite in 1997 April 7, 11, and 16 during a phase of high activity at TeV energies, as monitored with the Whipple, HEGRA, and CAT Cherenkov telescopes. Over the whale 0.1-200 keV range, the spectrum was exceptionally hard (alpha less than or equal to 1, with F-v proportional to nu(-alpha)), indicating that the X-ray power output peaked at (or above) similar to 100 keV. This represents a shift of at least 2 orders of magnitude with respect to previous observations of Mrk 501, a behavior never seen before in this or any other blazar. The overall X-ray spectrum hardens with increasing intensity, and at each epoch it is softer at larger energies. The correlated variability from soft X-rays to the TeV band points to models in which the same population of relativistic electrons produces the X-ray continuum via synchrotron radiation and the TeV emission by inverse Compton scattering of the synchrotron photons or other seed photons. Forthe first lime in any blazar, the synchrotron power is observed to peak at hard X-ray energies. The large shift of the synchrotron peak frequency with respect to previous observations of Mrk 501 implies that intrinsic changes in the relativistic electron spectrum caused the increase in emitted power. Due to the very high electron energies, the inverse Compton process is limited by the Klein-Nishina regime. This implies a quasi-linear (as opposed to quadratic) relation of the variability amplitude in the TeV and hard X-ray ranges (for the synchrotron self-Compton model) and an increase of the inverse Compton peak frequencysmaller than that of the synchrotron peak frequency.

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Documento generato il 18/11/17 alle ore 03:48:05