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Normalizing a relativistic model of X-ray reflection: Definition of the reflection fraction and its implementation in relxill

Dauser, T. and García, J. and Walton, D. J. and Eikmann, W. and Kallman, T. and McClintock, J. and Wilms, J. (2016) Normalizing a relativistic model of X-ray reflection: Definition of the reflection fraction and its implementation in relxill. Astronomy and Astrophysics, 590 . Art. No. A76. ISSN 0004-6361. https://resolver.caltech.edu/CaltechAUTHORS:20160715-103832095

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Abstract

Aims. The only relativistic reflection model that implements a parameter relating the intensity incident on an accretion disk to the observed intensity is relxill. The parameter used in earlier versions of this model, referred to as the reflection strength, is unsatisfactory; it has been superseded by a parameter that provides insight into the accretion geometry, namely the reflection fraction. The reflection fraction is defined as the ratio of the coronal intensity illuminating the disk to the coronal intensity that reaches the observer. Methods. The relxill model combines a general relativistic ray-tracing code and a photoionization code to compute the component of radiation reflected from an accretion that is illuminated by an external source. The reflection fraction is a particularly important parameter for relativistic models with well-defined geometry, such as the lamp post model, which is a focus of this paper. Results. Relativistic spectra are compared for three inclinations and for four values of the key parameter of the lamp post model, namely the height above the black hole of the illuminating, on-axis point source. In all cases, the strongest reflection is produced for low source heights and high spin. A low-spin black hole is shown to be incapable of producing enhanced relativistic reflection. Results for the relxill model are compared to those obtained with other models and a Monte Carlo simulation. Conclusions. Fitting data by using the relxill model and the recently implemented reflection fraction, the geometry of a system can be constrained. The reflection fraction is independent of system parameters such as inclination and black hole spin. The reflection-fraction parameter was implemented with the name refl_frac in all flavours of the relxill model, and the non-relativistic reflection model xillver, in v0.4a (18 January 2016).


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1051/0004-6361/201628135DOIArticle
http://arxiv.org/abs/1601.03771arXivDiscussion Paper
ORCID:
AuthorORCID
Dauser, T.0000-0003-4583-9048
García, J.0000-0003-3828-2448
Walton, D. J.0000-0001-5819-3552
Kallman, T.0000-0002-5779-6906
Wilms, J.0000-0003-2065-5410
Additional Information:© 2016 ESO. Received 14 January 2016. Accepted 13 April 2016. Published online 13 May 2016. We thank John E. Davis for the development of the SLxfig module used to prepare the figures in this Research Note and Andrzej Zdziarski for helpful comments. This research has made use of ISIS functions (ISISscripts) provided by ECAP/Remeis observatory and MIT (http://www.sternwarte. uni-erlangen.de/isis/). We also thank the anonymous referee for comments that improved the manuscript.
Group:Space Radiation Laboratory
Subject Keywords:accretion, accretion disks line: profiles galaxies: active X-rays: galaxies
Record Number:CaltechAUTHORS:20160715-103832095
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160715-103832095
Official Citation:Normalizing a relativistic model of X-ray reflection - Definition of the reflection fraction and its implementation in relxill T. Dauser, J. García, D. J. Walton,, W. Eikmann, T. Kallman, J. McClintock and J. Wilms A&A, 590 (2016) A76 DOI: http://dx.doi.org/10.1051/0004-6361/201628135
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69054
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:15 Jul 2016 18:03
Last Modified:17 Dec 2019 23:27

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