# The method of transfer functions to describe GR effects in spectra and polarisation from black-hole accretion disks

## TL;DR

This paper reviews a transfer function approach to efficiently model and analyze the effects of General Relativity on spectra and polarization from black-hole accretion disks, aiding interpretation of upcoming X-ray polarimetry data.

## Contribution

It develops a transfer function method to accelerate GR effect computations in spectra and polarization modeling of black-hole accretion disks, facilitating data fitting and analysis.

## Key findings

- Transfer functions enable faster GR spectrum simulations.
- Method supports modeling of polarization properties.
- Prepared for upcoming X-ray polarimetry missions.

## Abstract

We briefly review a fruitful approach to compute a variety of radiation signatures of General Relativity (GR) originating from accretion disks in strong gravity. A set of transfer functions can be pre-computed and then employed to accelerate the ray-traycing computations, generate a series of model spectra, and to fit the model predictions to actual data sets in X-rays. We have been developing this method to examine spectra and light curves and to model the expected polarimetric properties; in particular, to analyse the properties of the "corona--disk-line" geometry with GR effects taken into account. New impetus to this activity is emerging in the anticipation of upcoming missions equipped with the sensitivity to polarimetric properties in X-rays: IXPE (Imaging X-Ray Polarimetry Explorer) and eXTP (enhanced X-ray Timing and Polarimetry mission).