Recurring obscuration in NGC 3783

被引：22

作者：

Kaastra, J. S. ^{[1
,2
]}

Mehdipour, M. ^{[1
]}

Behar, E. ^{[3
]}

Bianchi, S. ^{[4
]}

Branduardi-Raymont, G. ^{[5
]}

Brenneman, L. ^{[6
]}

Cappi, M. ^{[7
]}

Costantini, E. ^{[1
]}

De Marco, B. ^{[8
]}

di Gesu, L. ^{[9
]}

Ebrero, J. ^{[10
]}

Kriss, G. A. ^{[11
]}

Mao, J. ^{[1
,2
]}

Peretz, U. ^{[3
]}

Petrucci, P-O ^{[12
]}

Ponti, G. ^{[13
]}

Walton, D. ^{[14
]}

机构：

[1] SRON Netherlands Inst Space Res, Sorbonnelaan 2, NL-3584 CA Utrecht, Netherlands

[2] Leiden Univ, Leiden Observ, POB 9513, NL-2300 RA Leiden, Netherlands

[3] Technion Israel Inst Technol, Dept Phys, IL-32000 Haifa, Israel

[4] Univ Roma Tre, Dipartimento Matemat & Fis, Via Vasca Navale 84, I-00146 Rome, Italy

[5] Univ Coll London, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England

[6] Smithsonian Astrophys Observ, Cambridge, MA USA

[7] INAF IASF Bologna, Via Gobetti 101, I-40129 Bologna, Italy

[8] Polish Acad Sci, Nicolaus Copernicus Astron Ctr, Bartycka 18, PL-00716 Warsaw, Poland

[9] Univ Geneva, Dept Astron, 16 Ch Ec, CH-1290 Versoix, Switzerland

[10] European Space Astron Ctr, POB 78, Madrid 28691, Spain

[11] Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA

[12] Univ Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France

[13] Max Planck Inst Extraterr Phys, D-85748 Garching, Germany

[14] Inst Astron, Madingley Rd, Cambridge CB3 0HA, England

来源：

ASTRONOMY & ASTROPHYSICS | 2018年 / 619卷

基金：

欧盟地平线“2020”;

关键词：

X-rays: galaxies; galaxies: active; galaxies: Seyfert; galaxies: individual: NGC3783; techniques: spectroscopic; RAY; REGION; AGN;

D O I：

10.1051/0004-6361/201832629

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Context. Obscuration of the continuum emission from active galactic nuclei by streams of gas with relatively high velocity (> 1000 km s(-1)) and column density (> 3 x 10(25) m(-2)) has been seen in a few Seyfert galaxies. This obscuration has a transient nature. In December 2016 we witnessed such an event in NGC3783. Aims. The frequency and duration of these obscuration events is poorly known. Here we study archival data of NGC3783 in order to constrain this duty cycle. Methods. We use archival Chandra/NuSTAR spectra taken in August 2016. We also study the hardness ratio of all Swift XRT spectra taken between 2008 and 2017. Results. In August 2016, NGC3783 also showed evidence of obscuration. While the column density of the obscuring material is ten times lower than in December 2016, the opacity is still sufficient to block a significant fraction of the ionising X-ray and extreme ultraviolet photons. From the Swift hardness ratio behaviour we find several other epochs with obscuration. Obscuration with columns > 10(26) m(-2) may take place about half of the time. Also, in archival X-ray data taken by the Advanced Satellite for Cosmology and Astrophysics (ASCA) in 1993 and 1996 we find evidence of obscuration. Conclusions. Obscuration of the ionising photons in NGC3783 occurs more frequently than previously thought. This may not always have been recognised due to low-spectral-resolution observations, overly limited spectral bandwidth or confusion with underlying continuum variations.

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