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Titolo:
Unveiling the AGN powering the "Composite" Seyfert/Star-forming galaxy NGC7679: BeppoSAX and ASCA results
Autore:
Della Ceca, R; Pellegrini, S; Bassani, L; Beckmann, V; Cappi, M; Palumbo, GGC; Trinchieri, G; Wolter, A;
Indirizzi:
Osserv Astron Brera, I-20121 Milan, Italy Osserv Astron Brera Milan Italy I-20121 tron Brera, I-20121 Milan, Italy Univ Bologna, Dipartimento Astron, I-40127 Bologna, Italy Univ Bologna Bologna Italy I-40127 imento Astron, I-40127 Bologna, Italy CNR, Ist TeSRE, I-40129 Bologna, Italy CNR Bologna Italy I-40129CNR, Ist TeSRE, I-40129 Bologna, Italy INTEGRAL Sci Data Ctr, CH-1290 Geneva, Switzerland INTEGRAL Sci Data Ctr Geneva Switzerland CH-1290 290 Geneva, Switzerland ASI, I-00198 Rome, Italy ASI Rome Italy I-00198ASI, I-00198 Rome, Italy
Titolo Testata:
ASTRONOMY & ASTROPHYSICS
fascicolo: 3, volume: 375, anno: 2001,
pagine: 781 - 790
SICI:
1432-0746(200109)375:3<781:UTAPT">2.0.ZU;2-S
Fonte:
ISI
Lingua:
ENG
Soggetto:
RAY ASTRONOMY SATELLITE; ACTIVE GALACTIC NUCLEI; EMISSION-LINE GALAXIES; STARBURST GALAXIES; ON-BOARD; CLASSIFICATION; REGION; VIEW;
Keywords:
galaxies : active; galaxies : individual : NGC 7679; galaxies : Seyfert; galaxies : starburst; X-rays : galaxies;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
57
Recensione:
Indirizzi per estratti:
Indirizzo: Della Ceca, R Osserv Astron Brera, Via Brera 28, I-20121 Milan, Italy Osserv Astron Brera Via Brera 28 Milan Italy I-20121 Italy
Citazione:
R. Della Ceca et al., "Unveiling the AGN powering the "Composite" Seyfert/Star-forming galaxy NGC7679: BeppoSAX and ASCA results", ASTRON ASTR, 375(3), 2001, pp. 781-790

Abstract

We discuss BeppoSAX observations and archive ASCA data of NGC 7679, a nearby, nearly face-on SB0 galaxy in which starburst and AGN activities coexist. The X-ray observations reveal a bright (L-0.1.50 keV similar to 2.9 x 10(43) erg s(-1)) and variable source having a minimum observed doubling/halving time scale of similar to 10-20 ksec. A simple power law with photon index of Gamma similar to 1.75 and small absorption (N-H < 4 x 10(20) cm(-2)) can reproduce the NGC 7679 spectrum from 0.1 up to 50 keV. These X-ray properties are unambiguous signs of Seyfert 1 activity in the nucleus of NGC 7679. The starburst activity, revealed by the IR emission, optical spectroscopy and H<alpha> imaging, and dominating in the optical and IR bands, is clearly overwhelmed by the AGN in the X-ray band. Although, at first glance, this is similar to what is observed in other starburst-AGN galaxies (e.g. NGC6240, NGC 4945), most strikingly here and at odds with the above examples,the X-ray spectrum of NGC 7679 does not appear to be highly absorbed. The main peculiarity of objects like NGC 7679 is not the strength of their starburst but the apparent optical weakness of the Seyfert 1 nucleus when compared with its X-ray luminosity. To date NGC 7679 is one of the few Seyfert 1/Starburst composites for which the broad-band X-ray properties have been investigated in detail. The results presented here imply that optical and infrared spectroscopy could be highly inefficient in revealing the presence of an AGN in these kinds of objects, which instead is clearly revealed from X-ray spectroscopic and variability investigations.

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Documento generato il 05/12/20 alle ore 13:53:37