fixed wrong energy weighting in ISRF

Author: mlietzow

README.md

@@ -7,7 +7,7 @@
 [![bibcode](https://img.shields.io/badge/bibcode-2016A%26A...593A..87R-1c459b)](https://ui.adsabs.harvard.edu/abs/2016A&A...593A..87R)
 [![doi](https://img.shields.io/badge/doi-10.1051%2F0004--6361%2F201424930-fab70c)](https://doi.org/10.1051/0004-6361/201424930)
 [![License](https://img.shields.io/badge/License-GPLv3-blue)](https://www.gnu.org/licenses/gpl-3.0)
-[![Version](https://img.shields.io/badge/Version-4.13.01-bf0040)](https://img.shields.io/badge/Version-4.13.01-bf0040)
+[![Version](https://img.shields.io/badge/Version-4.13.02-bf0040)](https://img.shields.io/badge/Version-4.13.02-bf0040)
 
 is a 3D Monte Carlo radiative transfer code that
 

src/CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required (VERSION 3.13.4)
 PROJECT (POLARIS
-    VERSION 4.13.01
+    VERSION 4.13.02
     DESCRIPTION "POLARIS: POLArized RadIation Simulator, Copyright (C) 2018 Stefan Reissl"
     HOMEPAGE_URL "https://portia.astrophysik.uni-kiel.de/polaris/"
     LANGUAGES CXX

src/SourceISRF.cpp

@@ -209,7 +209,7 @@ void CSourceISRF::createNextRay(photon_package * pp, CRandomGenerator * rand_gen
     pp->updateCoordSystem(phi_direction, theta_direction);
 
     // weight photon energy accordingly
-    double exp_weight = pow(cos(theta_direction), 1.0 - bias_exp);
+    double exp_weight = 2.0 / (bias_exp + 1.0) * pow(cos(theta_direction), 1.0 - bias_exp);
     pp->setStokesVector(tmp_stokes_vector * exp_weight);
 }