blacklamp -- lamppost geometry

Intensity Profile of Accretion Disk in Lamppost Coronal Geometry

This C++ code calculates the intensity profile of the irradiation of the accretion disk by a point-like source located on the rotational axis of the black hole in the lamppost geometry. The generated data files can be used to tabulate and structure them into the file in .fits format using another script. The created .fits file can be used in the model relxilllp_nk, a relativistic reflection model in the lamppost geometry.

Cite the code:

When using blacklamp for your work, we also request to please cite the following papers:

• Public Release of RELXILL_NK: A Relativistic Reflection Model for Testing Einstein’s Gravity; A. B. Abdikamalov, D. Ayzenberg, C. Bambi, T. Dauser, J. A. Garcia et al.; Astrophys.J. 878 (2019) 2, 91
• Reflection Spectra of Accretion Disks Illuminated by Disk-like Coronae; S. Riaz, A. B. Abdikamalov, D. Ayzenberg, C. Bambi, H. Wang et al., Astrophys.J. 925 (2022) 1, 51

How to download

    git clone https://github.com/ABHModels/blacklamp.git --branch lamppost --single-branch

How to Run

In the standard from, the main.cpp file takes three input arguments:

    ./main a height mdot

where:

a is the spin parameter
height is the height of the source
mdot is the accretion rate of the black hole

The input parameters can be changed according to the medium setup.

Output

The code generates a data file in the data directory with the name lp_a_height_mdot.dat, where a, height, and mdot are the input parameters. The file contains the following columns:

rDisk: radial coordinate of the photons hitting the accretion disk
III: Intensity at the given radial points on the accretion disk

The output file can have more columns which are currently commented in the code:
ED: emission angle of the photons at the emission point on the source
HD: incident angle of the photons when they hit the accretion disk

Dependencies

The code depends on the following header files:

eqjohannsen.h and johannsen.h: header file for calculating the metric and other functions in Johannsen spacetime
rk45.h: header file for implementing the Runge-Kutta method for the differential equations

Notes

• The code uses the RK45 method to integrate the differential equations, and it requires the definition of the cache function in the johannsen.h header file. The cache function is used to store the metric and its derivatives for each point in the trajectory of the photon.

• The code is capable of performing the calculation in non-Kerr spacetime as well. The user can make the changes in the value of the deformation paramters within the code. The deformation paramter can also be very easily be set as an input paramter.

• The output file can be used to construct a .fits file using the generatefits.py script. The .fits file can then be used in the relxilllp_nk model for relativistic reflection in the lamppost geometry.

• Support contact: relxill_nk@fudan.edu.cn