The X-ray spectrum and variability of the Seyfert 2 galaxy NGC 7172 |
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| Authors: | M Guainazzi G Matt L A Antonelli F Fiore L Piro & S Ueno |
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| Institution: | SAX/SDC, Nuova Telespazio, Via Corcolle 19, I-00131 Roma, Italy,;UnitàGIFCO/CNR, Via Archirafi 36, I-90123 Palermo, Italy,;Dipartimento di Fisica, Universitàdegli Studi 'Roma Tre', Via della Vasca Navale 84, I-00146 Roma, Italy,;Osservatorio Astronomico di Roma, Via dell'Osservatorio, I-00044 Monteporzio-Catone, Italy,;Istituto di Astrofisica Spaziale, CNR, Via Fosso del Cavaliere, I-00133 Roma, Italy,;X-ray Astronomy Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH |
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| Abstract: | We present evidence of flux variability, on both short (hours) and long (months) time-scales, of the Seyfert 2 galaxy NGC 7172. These results are based on the ASCA observation of NGC 7172 performed in 1996 May. The source was detected at a rather low flux level, about 3 times fainter than its usual state (including 1 yr before, when it was also observed by ASCA ). The source also varied by about 30 per cent during the observation, confirming the presence of a type 1 nucleus in its centre. However, its spectrum appears to be flatter than the typical Seyfert 1 spectrum (in agreement with findings on other Seyfert 2s), posing problems for the unification model unless complex absorption is invoked. |
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| Keywords: | galaxies: individual: NGC 7172 galaxies: Seyfert X-rays: galaxies |
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