`RELXILL`Model v0.5b

`RELXILL` is a new reflection 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.

v0.5b The xillver model
calculated for the nthcomp primary continuum (called
`xillverCp`) is now also included in the distributed model
code.

v0.5a Major updated now adding the possibility to use a "nthcomp" continuum for the (relativistic) reflection. The new models are named with a "Cp" (see below for a detailed description) and require a new xillver table to be downloaded. Additionally the possibility to re-normalize the relxill models (any type) was added, which eases the burden on the fit algorithm, as normally a change in height, e.g., also changes the normalization. It can be activated by setting the environment variable "RELXILL_RENORM=1".

### 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 component will be returned (similar to the pexrav model definition). The detailed definition of the reflection fraction can be found here: Dauser+2016, A&A, 590, A76. 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. The
"table_nthcomp.tgz" is optional, but necessary if you want to use the
reflection models with a `nthcomp` input continuum.

last changes | in version | |

relxill_code.tgz | 2017-02-22 | v0.5b |

tables.fits.tgz (warning: 938MB) | 2016-12-21 | v0.4e |

table_nthcomp.tgz (warning: 906MB) | 2017-02-17 | v0.5a |

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.

The environment variable RELXILL_NUM_BINS can be used to set the
internal number of bins on which `RELXILL` is
calculated. This will speed up the calculation by a large amount but
might produce incorrect results if set to low (see model description
below for more information on how to use it).

The `relxill` models in the lamp post geometry are using the
physically predicted normalization assuming a constant primary source
flux. Due to gravitational redshift effects this might change for the
observer and therefore the normalization of the model strongly depends
on the height if the primary source. However, this behavior might
create problems for fit algorithm. A re-normalization can therefore be
forced by setting the environment variable "RELLINE_RENORM=1".

### A Comparison between `RELXILL` and the angle averaged approach

`RELXILL`(standard parameters: logxi=2, gamma=2, index=3, spin=0.99). Middle: Ratio between relxill and the conventional relconv*xillver. Right: Relative 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.