New Model: RELXILL v0.4a
2016-01-18

RELXILL is a brand new model, joining forces of the XILLVER reflection code (link; Garcia et al., 2010, 2011, 2013) and the RELLINE code (Dauser et al., 2010, 2013). The striking new feature is that for each point on the disk the proper xillver-reflection spectrum is chosen for each relativistically calculated emission angle. The implications of this improvement and more details regarding the model are provided in Garcia & Dauser et al. (2014, ApJ, 782, 76) and Dauser & Garcia et al. (2014, MNRAS, 444, L100). See also this pdf for a short information on all models and their parameters. A full list of changes of previous versions can be found here.

v0.4a: A bug was found in the reflection fraction in v0.3a. Any reflection fraction obtained with v0.3a can therefore unfortunately not be trusted and has to be re-computed with new version . We would like to stress that this does not affect the spectral shape, but only the value of the reflection fraction obtained from the fit. The only exception is if the reflected and primary spectrum was fixed using fixReflFrac=1 and therefore also the complete spectral shape was affected by this bug.
Along with the fix of the reflection fraction, the normalization of relxill was also revised. It is now consistently set to follow the xillver normalization, but including all relativistic effects. Additionally the angleon parameter was removed from the parameter list (setting it to angleon=1).
Due to several misunderstandings, the definition of the reflection fraction was revised. In order to provide a concise and detailed overview, this was done as a research note (submitted to A&A). It can be found here: http://arxiv.org/abs/1601.03771.

angle_image.png

Figure of an accretion disk, showing the predicted emission angle from GR ray tracing (upper panel: inclination 40°; lower panel: 80°; Garcia & Dauser, 2014, accepted by ApJ). It is evident that the emission angle at the inner parts, where most of the radiation is expected, does differ largely from the inclination angle. Therefore a proper relativstic treatment is necessary to take the angular effects into account.

General Information

By installing the new RELXILL model, all previous implementations of the relline-like and relconv-like models are automatically installed, too. These models are completely identical to the ones from the RELLINE installation (hence, no additional installation of relline is necessary to get the previous functionalities).

Usage and Parameters

The RELXILL model now includes by default the irradiating power law source. It's strength can be set by the parameter refl_frac. This reflection fraction is defined as the ratio of photons that hit the disk to those that reach infinity. Due to strong light bending effects, this value can easily be larger than 1. More details can be found in Dauser+2014. Note, that for a negative value of refl_frac, only the reflection compontent will be returned (similar to the pexrav model definition). The detailed definition of the reflection fraction can be found here (Research Note accepted for publication in A&A): http://arxiv.org/abs/1601.03771. All information about the parameters of all relxill flavor models can also be found in this pdf: download

norm: defined as the normalization of xillver, including relativistic effects
refl_frac: reflection fraction: see RN for details (differences in the exact definition between relxill and relxilllp, as it depends on the geometry)
Ecut: cutoff energy in keV (the same for the power law and the reflection spectrum)
1: take angles properly into account
fixReflFrac: 0: free reflection fraction (determined by the refl_frac parameter)
1: fix reflection fraction to the lamp post value (i.e., the parameter refl_frac has NO meaning in this case)
2: free, (same as 1:), but now the reflection fraction is displayed on the screen

The meaning of the parameters is the same as for the separate models (see relline description). Moreover, as the angular effects are properly treated, no "guess" regarding a limb brightening or darkening law is needed anymore.

Download

To install, please download the following files:

last changes in version
relxill_code.tgz 2016-01-18 v0.4a
tables.fits.tgz (warning: 849MB) 2016-01-18 v0.4a

The installation is similar to the relline model (look here). Note that you can use the environment variable RELLINE_TABLES to point to the complete set of provided tables, including the xillver table.

A Comparison between RELXILL and the angle averaged approach

relxill_spectrum

Relativistically smeared spectra using RELXILL (standard parameters: logxi=2, gamma=2, index=3, spin=0.99). Middle: Ratio between relxill and the conventional relconv*xillver. Right: Relativ distribution of flux for different emission angles. Note the angle averaged approach, which is commonly used, assumes a flat distribution here.

The code here is still in BETA-test! Please contact me if you find bugs or encounter problems with the model.