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, D. Walton

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

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 × 1025 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 >1026 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.

Original languageEnglish
Article numberA112
Number of pages9
JournalAstronomy and Astrophysics
Volume619
Early online date13 Nov 2018
DOIs
Publication statusPublished - 30 Nov 2018

Fingerprint

occultation
hardness
astrophysics
cosmology
spectral resolution
continuums
gas
Seyfert galaxies
confusion
photons
opacity
active galactic nuclei
x rays
time measurement
bandwidth
cycles
gases

Keywords

  • Galaxies: Active
  • Galaxies: Individual: NGC 3783
  • Galaxies: Seyfert
  • Techniques: Spectroscopic
  • X-Rays: Galaxies

Cite this

Kaastra, J. S., Mehdipour, M., Behar, E., Bianchi, S., Branduardi-Raymont, G., Brenneman, L., ... Walton, D. (2018). Recurring obscuration in NGC 3783. Astronomy and Astrophysics, 619, [A112]. https://doi.org/10.1051/0004-6361/201832629
Kaastra, J. S. ; Mehdipour, M. ; Behar, E. ; Bianchi, S. ; Branduardi-Raymont, G. ; Brenneman, L. ; Cappi, M. ; Costantini, E. ; De Marco, B. ; Di Gesu, L. ; Ebrero, J. ; Kriss, G. A. ; Mao, J. ; Peretz, U. ; Petrucci, P. O. ; Ponti, G. ; Walton, D. / Recurring obscuration in NGC 3783. In: Astronomy and Astrophysics. 2018 ; Vol. 619.
@article{1d609510ccda4a688668fe5adf68d899,
title = "Recurring obscuration in NGC 3783",
abstract = "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 × 1025 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 >1026 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.",
keywords = "Galaxies: Active, Galaxies: Individual: NGC 3783, Galaxies: Seyfert, Techniques: Spectroscopic, X-Rays: Galaxies",
author = "Kaastra, {J. S.} and M. Mehdipour and E. Behar and S. Bianchi and G. Branduardi-Raymont and L. Brenneman and M. Cappi and E. Costantini and {De Marco}, B. and {Di Gesu}, L. and J. Ebrero and Kriss, {G. A.} and J. Mao and U. Peretz and Petrucci, {P. O.} and G. Ponti and D. Walton",
year = "2018",
month = "11",
day = "30",
doi = "10.1051/0004-6361/201832629",
language = "English",
volume = "619",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",

}

Kaastra, JS, Mehdipour, M, Behar, E, Bianchi, S, Branduardi-Raymont, G, Brenneman, L, Cappi, M, Costantini, E, De Marco, B, Di Gesu, L, Ebrero, J, Kriss, GA, Mao, J, Peretz, U, Petrucci, PO, Ponti, G & Walton, D 2018, 'Recurring obscuration in NGC 3783', Astronomy and Astrophysics, vol. 619, A112. https://doi.org/10.1051/0004-6361/201832629

Recurring obscuration in NGC 3783. / Kaastra, J. S.; Mehdipour, M.; Behar, E.; Bianchi, S.; Branduardi-Raymont, G.; Brenneman, L.; Cappi, M.; Costantini, E.; De Marco, B.; Di Gesu, L.; Ebrero, J.; Kriss, G. A.; Mao, J.; Peretz, U.; Petrucci, P. O.; Ponti, G.; Walton, D.

In: Astronomy and Astrophysics, Vol. 619, A112, 30.11.2018.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Recurring obscuration in NGC 3783

AU - Kaastra, J. S.

AU - Mehdipour, M.

AU - Behar, E.

AU - Bianchi, S.

AU - Branduardi-Raymont, G.

AU - Brenneman, L.

AU - Cappi, M.

AU - Costantini, E.

AU - De Marco, B.

AU - Di Gesu, L.

AU - Ebrero, J.

AU - Kriss, G. A.

AU - Mao, J.

AU - Peretz, U.

AU - Petrucci, P. O.

AU - Ponti, G.

AU - Walton, D.

PY - 2018/11/30

Y1 - 2018/11/30

N2 - 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 × 1025 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 >1026 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.

AB - 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 × 1025 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 >1026 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.

KW - Galaxies: Active

KW - Galaxies: Individual: NGC 3783

KW - Galaxies: Seyfert

KW - Techniques: Spectroscopic

KW - X-Rays: Galaxies

U2 - 10.1051/0004-6361/201832629

DO - 10.1051/0004-6361/201832629

M3 - Article

VL - 619

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

M1 - A112

ER -

Kaastra JS, Mehdipour M, Behar E, Bianchi S, Branduardi-Raymont G, Brenneman L et al. Recurring obscuration in NGC 3783. Astronomy and Astrophysics. 2018 Nov 30;619. A112. https://doi.org/10.1051/0004-6361/201832629