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Title: X-ray Luminosity and Absorption Column Fluctuations in the H2O Maser Galaxy NGC 4258 from Weeks to Years

Abstract

The authors report monitoring of the 0.3-10 keV spectrum of NGC 4258 with the XMM-Newton observatory at five epochs over 1.5 years. They also report reprocessing of an overlapping four epoch series of archival Chandra observations (0.5-10 keV). By including earlier ASCA and Beppo-SAX observations, they present a new, nine year time-series of models fit to the X-ray spectrum of NGC 4258. They model the Chandra and XMM-Newton data self-consistently with partially absorbed, hard power-law, soft thermal plasma, and soft power-law components. Over the nine years, the photo-electric absorbing column ({approx} 10{sup 23} cm{sup -2}) did not vary detectably, except for a {approx} 40% drop between two ASCA epochs separated by 3 years (in 1993 and 1996) and a {approx} 60% rise between two XMM-Newton epochs separated by just 5 months (in 2001 and 2002). In contrast, factor of 2-3 changes are seen in absorbed flux on the timescale of years. These are uncorrelated with changes in absorbing column and indicative of central engine variability. The most rapid change in luminosity (5-10 keV) that the authors detect (with XMM-Newton and Chandra) is on the order of 30% over 19 days. The warped disk that is a known source of H{submore » 2}O maser emission in NGC 4258 is believed to cross the line of sight to the central engine. They propose that the variations in absorbing column arise from inhomogeneities in the rotating disk, as they sweep across the line of sight. They estimate that the inhomogeneities are {approx} 10{sup 15} cm in size.« less

Authors:
Publication Date:
Research Org.:
Stanford Linear Accelerator Center, Menlo Park, CA (US)
Sponsoring Org.:
USDOE Office of Science (US)
OSTI Identifier:
829725
Report Number(s):
SLAC-PUB-10572
TRN: US0405828
DOE Contract Number:
AC03-76SF00515
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 30 Jul 2004
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; ABSORPTION; ENGINES; FLUCTUATIONS; LUMINOSITY; MASERS; MONITORING; PLASMA; REPROCESSING

Citation Formats

Argon, A. X-ray Luminosity and Absorption Column Fluctuations in the H2O Maser Galaxy NGC 4258 from Weeks to Years. United States: N. p., 2004. Web. doi:10.2172/829725.
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Argon, A. X-ray Luminosity and Absorption Column Fluctuations in the H2O Maser Galaxy NGC 4258 from Weeks to Years. United States. doi:10.2172/829725.
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Argon, A. Fri . "X-ray Luminosity and Absorption Column Fluctuations in the H2O Maser Galaxy NGC 4258 from Weeks to Years". United States. doi:10.2172/829725. https://www.osti.gov/servlets/purl/829725.
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@article{osti_829725,
title = {X-ray Luminosity and Absorption Column Fluctuations in the H2O Maser Galaxy NGC 4258 from Weeks to Years},
author = {Argon, A.},
abstractNote = {The authors report monitoring of the 0.3-10 keV spectrum of NGC 4258 with the XMM-Newton observatory at five epochs over 1.5 years. They also report reprocessing of an overlapping four epoch series of archival Chandra observations (0.5-10 keV). By including earlier ASCA and Beppo-SAX observations, they present a new, nine year time-series of models fit to the X-ray spectrum of NGC 4258. They model the Chandra and XMM-Newton data self-consistently with partially absorbed, hard power-law, soft thermal plasma, and soft power-law components. Over the nine years, the photo-electric absorbing column ({approx} 10{sup 23} cm{sup -2}) did not vary detectably, except for a {approx} 40% drop between two ASCA epochs separated by 3 years (in 1993 and 1996) and a {approx} 60% rise between two XMM-Newton epochs separated by just 5 months (in 2001 and 2002). In contrast, factor of 2-3 changes are seen in absorbed flux on the timescale of years. These are uncorrelated with changes in absorbing column and indicative of central engine variability. The most rapid change in luminosity (5-10 keV) that the authors detect (with XMM-Newton and Chandra) is on the order of 30% over 19 days. The warped disk that is a known source of H{sub 2}O maser emission in NGC 4258 is believed to cross the line of sight to the central engine. They propose that the variations in absorbing column arise from inhomogeneities in the rotating disk, as they sweep across the line of sight. They estimate that the inhomogeneities are {approx} 10{sup 15} cm in size.},
doi = {10.2172/829725},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jul 30 00:00:00 EDT 2004},
month = {Fri Jul 30 00:00:00 EDT 2004}
}
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DOI:  10.2172/829725
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