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Title: PATCHY ACCRETION DISKS IN ULTRA-LUMINOUS X-RAY SOURCES

Abstract

The X-ray spectra of the most extreme ultra-luminous X-ray sources—those with L ≥ 10{sup 40} erg s{sup –1}—remain something of a mystery. Spectral roll-over in the 5-10 keV band was originally detected in the deepest XMM-Newton observations of the brightest sources; this is confirmed in subsequent NuSTAR spectra. This emission can be modeled via Comptonization, but with low electron temperatures (kT{sub e} ≅ 2 keV) and high optical depths (τ ≅ 10) that pose numerous difficulties. Moreover, evidence of cooler thermal emission that can be fit with thin disk models persists, even in fits to joint XMM-Newton and NuSTAR observations. Using NGC 1313 X-1 as a test case, we show that a patchy disk with a multiple temperature profile may provide an excellent description of such spectra. In principle, a number of patches within a cool disk might emit over a range of temperatures, but the data only require a two-temperature profile plus standard Comptonization, or three distinct blackbody components. A mechanism such as the photon bubble instability may naturally give rise to a patchy disk profile, and could give rise to super-Eddington luminosities. It is possible, then, that a patchy disk (rather than a disk with a standard single-temperature profile)more » might be a hallmark of accretion disks close to or above the Eddington limit. We discuss further tests of this picture and potential implications for sources such as narrow-line Seyfert-1 galaxies and other low-mass active galactic nuclei.« less

Authors:
 [1]; ; ;  [2]; ; ;  [3]
  1. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States)
  2. Universite de Toulouse, UPS-OMP, IRAP, F- 31100 Toulouse (France)
  3. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22365917
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 785; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; BLACK HOLES; BUBBLES; COSMIC X-RAY SOURCES; ELECTRON TEMPERATURE; GALAXY NUCLEI; KEV RANGE; MASS; POTENTIALS; SEYFERT GALAXIES; STAR CLUSTERS; X RADIATION; X-RAY SPECTRA

Citation Formats

Miller, J. M., Bachetti, M., Barret, D., Webb, N. A., Harrison, F. A., Walton, D. J., Rana, V., and Fabian, A. C., E-mail: jonmm@umich.edu. PATCHY ACCRETION DISKS IN ULTRA-LUMINOUS X-RAY SOURCES. United States: N. p., 2014. Web. doi:10.1088/2041-8205/785/1/L7.
Miller, J. M., Bachetti, M., Barret, D., Webb, N. A., Harrison, F. A., Walton, D. J., Rana, V., & Fabian, A. C., E-mail: jonmm@umich.edu. PATCHY ACCRETION DISKS IN ULTRA-LUMINOUS X-RAY SOURCES. United States. https://doi.org/10.1088/2041-8205/785/1/L7
Miller, J. M., Bachetti, M., Barret, D., Webb, N. A., Harrison, F. A., Walton, D. J., Rana, V., and Fabian, A. C., E-mail: jonmm@umich.edu. 2014. "PATCHY ACCRETION DISKS IN ULTRA-LUMINOUS X-RAY SOURCES". United States. https://doi.org/10.1088/2041-8205/785/1/L7.
@article{osti_22365917,
title = {PATCHY ACCRETION DISKS IN ULTRA-LUMINOUS X-RAY SOURCES},
author = {Miller, J. M. and Bachetti, M. and Barret, D. and Webb, N. A. and Harrison, F. A. and Walton, D. J. and Rana, V. and Fabian, A. C., E-mail: jonmm@umich.edu},
abstractNote = {The X-ray spectra of the most extreme ultra-luminous X-ray sources—those with L ≥ 10{sup 40} erg s{sup –1}—remain something of a mystery. Spectral roll-over in the 5-10 keV band was originally detected in the deepest XMM-Newton observations of the brightest sources; this is confirmed in subsequent NuSTAR spectra. This emission can be modeled via Comptonization, but with low electron temperatures (kT{sub e} ≅ 2 keV) and high optical depths (τ ≅ 10) that pose numerous difficulties. Moreover, evidence of cooler thermal emission that can be fit with thin disk models persists, even in fits to joint XMM-Newton and NuSTAR observations. Using NGC 1313 X-1 as a test case, we show that a patchy disk with a multiple temperature profile may provide an excellent description of such spectra. In principle, a number of patches within a cool disk might emit over a range of temperatures, but the data only require a two-temperature profile plus standard Comptonization, or three distinct blackbody components. A mechanism such as the photon bubble instability may naturally give rise to a patchy disk profile, and could give rise to super-Eddington luminosities. It is possible, then, that a patchy disk (rather than a disk with a standard single-temperature profile) might be a hallmark of accretion disks close to or above the Eddington limit. We discuss further tests of this picture and potential implications for sources such as narrow-line Seyfert-1 galaxies and other low-mass active galactic nuclei.},
doi = {10.1088/2041-8205/785/1/L7},
url = {https://www.osti.gov/biblio/22365917}, journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 1,
volume = 785,
place = {United States},
year = {Thu Apr 10 00:00:00 EDT 2014},
month = {Thu Apr 10 00:00:00 EDT 2014}
}