X-ray reprocessing by a molecular torus in the seyfert 1.9 galaxy NGC 2992

K. A. Weaver, J. Nousek, T. Yaqoob, R. F. Mushotzky, F. Makino, C. Otani

Research output: Contribution to journalArticle

55 Citations (Scopus)

Abstract

We present new X-ray spectral data for the Seyfert 1.9 galaxy NGC 2992 obtained with the Advanced Satellite for Cosmology and Astrophysics (ASCA). These data are combined with archival and published data to outline a 16 year history of flux variability in the X-ray band. We find that, while the 2-10 keV flux has decreased by a factor of ∼ 20 in 16 yr, the flux of the Fe Kα fluorescence line has decreased by only a factor of 2-3, and the inferred amount of Compton reflection is 5 times stronger compared to the continuum than 16 yr ago. From the delay in the response of the Fe K line and inferred Compton reflection to decreases in the continuum flux, we estimate that the reprocessed flux lags the continuum flux by ∼ 10 yr, giving a distance of ∼3.2 pc to the reprocessor. The observed time delay, along with the fact that the Fe K line is narrow (<6600 km s-1 FWHM), essentially rules out reprocessing in an accretion disk. This implies the existence of dense, neutral gas with NH ∼ 1023-1025 cm-2 within the central regions of the galaxy in addition to a disk, as might be expected for a molecular torus. We find that the flux in the ∼ 0.1-4 keV soft X-ray band has decreased by a factor of ∼ 15 in 14 yr, similar to the flux in the 2-10 keV band. In addition, the ASCA data, when combined with prior spectral results, imply the presence of a soft excess that is well modeled with partial covering of the nuclear continuum source. We have searched for and found no significant evidence for extended X-ray emission in the ROSAT HRI image of NGC 2992. This lack of extent, coupled with the observed long-term variability of the soft X-ray flux and spectral results for the soft excess, imply that the soft X-ray emission from NGC 2992 is nuclear in origin and is not due to scattering.

Original languageEnglish (US)
Pages (from-to)160-171
Number of pages12
JournalAstrophysical Journal
Volume458
Issue number1 PART I
DOIs
StatePublished - Jan 1 1996

Fingerprint

Seyfert galaxies
x rays
astrophysics
cosmology
continuums
K lines
time lag
reprocessing
fluorescence
accretion
scattering
neutral gases
accretion disks
coverings
history
gas
histories
galaxies

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Weaver, K. A., Nousek, J., Yaqoob, T., Mushotzky, R. F., Makino, F., & Otani, C. (1996). X-ray reprocessing by a molecular torus in the seyfert 1.9 galaxy NGC 2992. Astrophysical Journal, 458(1 PART I), 160-171. https://doi.org/10.1086/176800
Weaver, K. A. ; Nousek, J. ; Yaqoob, T. ; Mushotzky, R. F. ; Makino, F. ; Otani, C. / X-ray reprocessing by a molecular torus in the seyfert 1.9 galaxy NGC 2992. In: Astrophysical Journal. 1996 ; Vol. 458, No. 1 PART I. pp. 160-171.
@article{f692ea1017c54ce49d097efdaa0541eb,
title = "X-ray reprocessing by a molecular torus in the seyfert 1.9 galaxy NGC 2992",
abstract = "We present new X-ray spectral data for the Seyfert 1.9 galaxy NGC 2992 obtained with the Advanced Satellite for Cosmology and Astrophysics (ASCA). These data are combined with archival and published data to outline a 16 year history of flux variability in the X-ray band. We find that, while the 2-10 keV flux has decreased by a factor of ∼ 20 in 16 yr, the flux of the Fe Kα fluorescence line has decreased by only a factor of 2-3, and the inferred amount of Compton reflection is 5 times stronger compared to the continuum than 16 yr ago. From the delay in the response of the Fe K line and inferred Compton reflection to decreases in the continuum flux, we estimate that the reprocessed flux lags the continuum flux by ∼ 10 yr, giving a distance of ∼3.2 pc to the reprocessor. The observed time delay, along with the fact that the Fe K line is narrow (<6600 km s-1 FWHM), essentially rules out reprocessing in an accretion disk. This implies the existence of dense, neutral gas with NH ∼ 1023-1025 cm-2 within the central regions of the galaxy in addition to a disk, as might be expected for a molecular torus. We find that the flux in the ∼ 0.1-4 keV soft X-ray band has decreased by a factor of ∼ 15 in 14 yr, similar to the flux in the 2-10 keV band. In addition, the ASCA data, when combined with prior spectral results, imply the presence of a soft excess that is well modeled with partial covering of the nuclear continuum source. We have searched for and found no significant evidence for extended X-ray emission in the ROSAT HRI image of NGC 2992. This lack of extent, coupled with the observed long-term variability of the soft X-ray flux and spectral results for the soft excess, imply that the soft X-ray emission from NGC 2992 is nuclear in origin and is not due to scattering.",
author = "Weaver, {K. A.} and J. Nousek and T. Yaqoob and Mushotzky, {R. F.} and F. Makino and C. Otani",
year = "1996",
month = "1",
day = "1",
doi = "10.1086/176800",
language = "English (US)",
volume = "458",
pages = "160--171",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1 PART I",

}

Weaver, KA, Nousek, J, Yaqoob, T, Mushotzky, RF, Makino, F & Otani, C 1996, 'X-ray reprocessing by a molecular torus in the seyfert 1.9 galaxy NGC 2992', Astrophysical Journal, vol. 458, no. 1 PART I, pp. 160-171. https://doi.org/10.1086/176800

X-ray reprocessing by a molecular torus in the seyfert 1.9 galaxy NGC 2992. / Weaver, K. A.; Nousek, J.; Yaqoob, T.; Mushotzky, R. F.; Makino, F.; Otani, C.

In: Astrophysical Journal, Vol. 458, No. 1 PART I, 01.01.1996, p. 160-171.

Research output: Contribution to journalArticle

TY - JOUR

T1 - X-ray reprocessing by a molecular torus in the seyfert 1.9 galaxy NGC 2992

AU - Weaver, K. A.

AU - Nousek, J.

AU - Yaqoob, T.

AU - Mushotzky, R. F.

AU - Makino, F.

AU - Otani, C.

PY - 1996/1/1

Y1 - 1996/1/1

N2 - We present new X-ray spectral data for the Seyfert 1.9 galaxy NGC 2992 obtained with the Advanced Satellite for Cosmology and Astrophysics (ASCA). These data are combined with archival and published data to outline a 16 year history of flux variability in the X-ray band. We find that, while the 2-10 keV flux has decreased by a factor of ∼ 20 in 16 yr, the flux of the Fe Kα fluorescence line has decreased by only a factor of 2-3, and the inferred amount of Compton reflection is 5 times stronger compared to the continuum than 16 yr ago. From the delay in the response of the Fe K line and inferred Compton reflection to decreases in the continuum flux, we estimate that the reprocessed flux lags the continuum flux by ∼ 10 yr, giving a distance of ∼3.2 pc to the reprocessor. The observed time delay, along with the fact that the Fe K line is narrow (<6600 km s-1 FWHM), essentially rules out reprocessing in an accretion disk. This implies the existence of dense, neutral gas with NH ∼ 1023-1025 cm-2 within the central regions of the galaxy in addition to a disk, as might be expected for a molecular torus. We find that the flux in the ∼ 0.1-4 keV soft X-ray band has decreased by a factor of ∼ 15 in 14 yr, similar to the flux in the 2-10 keV band. In addition, the ASCA data, when combined with prior spectral results, imply the presence of a soft excess that is well modeled with partial covering of the nuclear continuum source. We have searched for and found no significant evidence for extended X-ray emission in the ROSAT HRI image of NGC 2992. This lack of extent, coupled with the observed long-term variability of the soft X-ray flux and spectral results for the soft excess, imply that the soft X-ray emission from NGC 2992 is nuclear in origin and is not due to scattering.

AB - We present new X-ray spectral data for the Seyfert 1.9 galaxy NGC 2992 obtained with the Advanced Satellite for Cosmology and Astrophysics (ASCA). These data are combined with archival and published data to outline a 16 year history of flux variability in the X-ray band. We find that, while the 2-10 keV flux has decreased by a factor of ∼ 20 in 16 yr, the flux of the Fe Kα fluorescence line has decreased by only a factor of 2-3, and the inferred amount of Compton reflection is 5 times stronger compared to the continuum than 16 yr ago. From the delay in the response of the Fe K line and inferred Compton reflection to decreases in the continuum flux, we estimate that the reprocessed flux lags the continuum flux by ∼ 10 yr, giving a distance of ∼3.2 pc to the reprocessor. The observed time delay, along with the fact that the Fe K line is narrow (<6600 km s-1 FWHM), essentially rules out reprocessing in an accretion disk. This implies the existence of dense, neutral gas with NH ∼ 1023-1025 cm-2 within the central regions of the galaxy in addition to a disk, as might be expected for a molecular torus. We find that the flux in the ∼ 0.1-4 keV soft X-ray band has decreased by a factor of ∼ 15 in 14 yr, similar to the flux in the 2-10 keV band. In addition, the ASCA data, when combined with prior spectral results, imply the presence of a soft excess that is well modeled with partial covering of the nuclear continuum source. We have searched for and found no significant evidence for extended X-ray emission in the ROSAT HRI image of NGC 2992. This lack of extent, coupled with the observed long-term variability of the soft X-ray flux and spectral results for the soft excess, imply that the soft X-ray emission from NGC 2992 is nuclear in origin and is not due to scattering.

UR - http://www.scopus.com/inward/record.url?scp=21344442577&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=21344442577&partnerID=8YFLogxK

U2 - 10.1086/176800

DO - 10.1086/176800

M3 - Article

AN - SCOPUS:21344442577

VL - 458

SP - 160

EP - 171

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 PART I

ER -

Weaver KA, Nousek J, Yaqoob T, Mushotzky RF, Makino F, Otani C. X-ray reprocessing by a molecular torus in the seyfert 1.9 galaxy NGC 2992. Astrophysical Journal. 1996 Jan 1;458(1 PART I):160-171. https://doi.org/10.1086/176800