SIGNIFICANT X-RAY LINE EMISSION IN THE 5-6 keV BAND OF NGC 4051
- Department of Physics, University of Maryland Baltimore County, Baltimore, MD 21250 (United States)
- Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom)
- Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG (United Kingdom)
- Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)
- Institute for Astrophysics and Computational Sciences, Department of Physics, Catholic University of America, Washington, DC 20064 (United States)
- Department of Physics and Astronomy, Georgia State University, Astronomy Offices, One Park Place South SE, Suite 700, Atlanta, GA 30303 (United States)
A Suzaku X-ray observation of NGC 4051 taken during 2005 November reveals line emission at 5.44 keV in the rest frame of the galaxy which does not have an obvious origin in known rest-frame atomic transitions. The improvement to the fit statistic when this line is accounted for establishes its reality at >99.9% confidence: we have also verified that the line is detected in the three X-ray Imaging Spectrometer units independently. Comparison between the data and Monte Carlo simulations shows that the probability of the line being a statistical fluctuation is p < 3.3 x 10{sup -4}. Consideration of three independent line detections in Suzaku data taken at different epochs yields a probability p < 3 x 10{sup -11} and thus conclusively demonstrates that it cannot be a statistical fluctuation in the data. The new line and a strong component of Fe Kalpha emission from neutral material are prominent when the source flux is low, during 2005. Spectra from 2008 show evidence for a line consistent with having the same flux and energy as that observed during 2005, but inconsistent with having a constant equivalent width against the observed continuum. The stability of the line flux and energy suggests that it may not arise in transient hotspots, as has been suggested for similar lines in other sources, but could arise from a special location in the reprocessor, such as the inner edge of the accretion disk. Alternatively, the line energy may be explained by spallation of Fe into Cr, as discussed in a companion paper.
- OSTI ID:
- 21394285
- Journal Information:
- Astrophysical Journal, Vol. 712, Issue 1; Other Information: DOI: 10.1088/0004-637X/712/1/209; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
MONTE CARLO METHOD
PHOTON EMISSION
PROBABILITY
SPALLATION
SPECTRA
SPECTROMETERS
X-RAY GALAXIES
CALCULATION METHODS
COSMIC RAY SOURCES
COSMIC X-RAY SOURCES
EMISSION
EVALUATION
GALAXIES
MEASURING INSTRUMENTS
NUCLEAR REACTIONS
SIMULATION