48
48
Jul 20, 2013
07/13
by
A. Garcia-Rissmann; A. Rodriguez-Ardila; T. A. A. Sigut; A. K. Pradhan
texts
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In AGN spectra, a series of FeII multiplets form a pseudo-continuum that extends from the ultraviolet to the near-infrared (NIR). This emission is believed to originate in the Broad Line Region (BLR), and it has been known for a long time that pure photoionization fails to reproduce it in the most extreme cases, as does the collisional-excitation alone. The most recent models by Sigut & Pradhan (2003) include details of the FeII ion microphysics and cover a wide range in ionization...
Source: http://arxiv.org/abs/1203.2949v1
82
82
Sep 23, 2013
09/13
by
D. Grupe; S. Komossa; L. C. Gallo; A. L. Longinotti; A. C. Fabian; A. K. Pradhan; M. Gruberbauer; D. Xu
texts
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The Narrow-line Seyfert 1 galaxy (NLS1) Mkn 335 is remarkable because it has repeatedly shown deep, long X-ray low-states which show pronounced spectral structure. It has become one of the prototype AGN in deep minimum X-ray states. Here we report on the continuation of our ongoing monitoring campaign with Swift and the examination of the low state X-ray spectra based on a 200 ks triggered observation with XMM in June 2009. Swift has continuously monitored Mkn 335 since May 2007 typically on a...
Source: http://arxiv.org/abs/1202.4692v2
77
77
Sep 21, 2013
09/13
by
J. Oelgoetz; C. J. Fontes; H. L. Zhang; M. Montenegro; S. N. Nahar; A. K. Pradhan
texts
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It is shown that above the temperature of maximum abundance, recombination rates into the excited states of He-like ions that are calculated using earlier, more approximate methods differ markedly from rates obtained from recent distorted-wave and R-Matrix calculations (unified recombination rate coefficients) for Ca, Fe, and Ni. The present rates lead to G ratios that are greatly lower than those resulting from the more approximate rates in previous works, by up to a factor of six at high...
Source: http://arxiv.org/abs/0709.0740v2
46
46
Sep 18, 2013
09/13
by
C. Mendoza; M. J. Seaton; P. Buerger; A. Bellorin; M. Melendez; J. Gonzalez; L. S. Rodriguez; F. Delahaye; E. Palacios; A. K. Pradhan; C. J. Zeippen
texts
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Codes to compute mean opacities and radiative accelerations for arbitrary chemical mixtures using the Opacity Project recently revised data have been restructured in a client--server architecture and transcribed as a subroutine library. This implementation increases efficiency in stellar modelling where element stratification due to diffusion processes is depth dependent, and thus requires repeated fast opacity reestimates. Three user modes are provided to fit different computing environments,...
Source: http://arxiv.org/abs/0704.1583v1
46
46
Sep 22, 2013
09/13
by
J. Oelgoetz; C. J. Fontes; H. L. Zhang; S. N. Nahar; A. K. Pradhan
texts
eye 46
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New, more detailed calculations of the emission spectra of the He-like K ALPHA complex of calcium, iron and nickel have been carried out using data from both distorted-wave and R-matrix calculations. The value of the GD ratio (an extended definition of the G ratio that accounts for the effect of resolved and unresolved satellite lines) is significantly enhanced at temperatures below the temperature of He-like maximum abundance. Furthermore it is shown that satellite lines are important...
Source: http://arxiv.org/abs/0811.2240v1
54
54
Sep 22, 2013
09/13
by
S. N. Nahar; J. Oelgoetz; A. K. Pradhan
texts
eye 54
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The unified method for total electron-ion recombination is extended to study the dielectronic satellite (DES) lines. These lines, formed from radiative decay of autoionizing states, are highly sensitive temperature diagnostics of astrophysical and laboratory plasma sources. The computation of the unified recombination rates is based on the relativistic Breit-Pauli R-matrix method and close coupling approximation. Extending the theoretical formulation developed earlier we present recombination...
Source: http://arxiv.org/abs/0811.2375v1
78
78
Jul 20, 2013
07/13
by
M. A. Bautista; P. Romano; A. K. Pradhan
texts
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We present ground state photoionization cross sections of atoms and ions averaged over resonance structures for photoionization modeling of astrophysical sources. The detailed cross sections calculated in the close-coupling approximation using the R-matrix method, with resonances delineated at thousands of energies, are taken from the Opacity Project database TOPbase and the Iron Project, including new data for the low ionization stages of iron Fe I--V. The resonance-averaged cross sections are...
Source: http://arxiv.org/abs/astro-ph/9712037v1
4
4.0
Jun 29, 2018
06/18
by
A. O. M. Marinello; A. Rodriguez-Ardila; A. Garcia-Rissmann; T. A. A. Sigut; A. K. Pradhan
texts
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We present a study of FeII emission in the near-infrared region (NIR) for 25 active galactic nuclei (AGNs) to obtain information about the excitation mechanisms that power it and the location where it is formed. We employ a NIR FeII template derived in the literature and found that it successfully reproduces the observed FeII spectrum. The FeII bump at 9200 Angstroms detected in all objects studied confirms that Lyman-alpha fluorescence is always present in AGNs. The The correlation found...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1602.05159
