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Recurring obscuration in NGC 3783

Kaastra, J. S. and Mehdipour, M. and Behar, E. and Bianchi, S. and Branduardi-Raymont, G. and Brenneman, L. and Cappi, M. and Costantini, E. and De Marco, B. and di Gesu, L. and Ebrero, J. and Kriss, G. A. and Mao, J. and Peretz, U. and Petrucci, P.-O. and Ponti, G. and Walton, D. (2018) Recurring obscuration in NGC 3783. Astronomy and Astrophysics, 619 . Art. No. A112. ISSN 0004-6361. doi:10.1051/0004-6361/201832629.

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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 × 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 NGC 3783. Aims. The frequency and duration of these obscuration events is poorly known. Here we study archival data of NGC 3783 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, NGC 3783 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 NGC 3783 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kaastra, J. S.0000-0001-5540-2822
Bianchi, S.0000-0002-4622-4240
Ebrero, J.0000-0001-5924-8818
Mao, J.0000-0001-7557-9713
Ponti, G.0000-0003-0293-3608
Walton, D.0000-0001-5819-3552
Additional Information:© 2018 ESO. Article published by EDP Sciences. Received 12 January 2018; Accepted 25 August 2018; Published online 13 November 2018. SRON is financially supported by NWO, The Netherlands Organization for Scientific Research. The research at the Technion is supported by the I-CORE program of the Planning and Budgeting Committee (grant number 1937/12). EB acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 655324. SB and MC acknowledge financial support from the Italian Space Agency under grant ASI-INAF I/037/12/0, and under the agreement ASI-INAF n.2017-14-H.O. BDM acknowledges support from Polish National Science Centre grant Polonez 2016/21/P/ST9/04025. POP aknowledges support from the CNES and French PNHE. GP acknowledges support by the Bundesministerium für Wirtschaft und Technologie/Deutsches Zentrum für Luftund Raumfahrt (BMWI/DLR, FKZ 50 OR 1604) and the Max Planck Society.
Subject Keywords:X-rays: galaxies – galaxies: active – galaxies: Seyfert – galaxies: individual: NGC3783 – techniques: spectroscopic
Record Number:CaltechAUTHORS:20180510-154544556
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Official Citation:Recurring obscuration in NGC 3783. J. S. Kaastra, M. Mehdipour, E. Behar, S. Bianchi, G. Branduardi-Raymont, L. Brenneman, M. Cappi, E. Costantini, B. De Marco, L. di Gesu, J. Ebrero, G. A. Kriss, J. Mao, U. Peretz, P.-O. Petrucci, G. Ponti and D. Walton. A&A, 619 (2018) A112. DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86358
Deposited By: Joy Painter
Deposited On:10 May 2018 22:59
Last Modified:15 Nov 2021 20:37

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