# The Boundary Layer in compact binaries

## TL;DR

This paper uses 1D hydrodynamical simulations to study the boundary layer in white dwarf binaries, analyzing how parameters affect luminosity and spectrum to interpret observations.

## Contribution

It introduces a 1D slim disk model with radiation transport and energy considerations to predict boundary layer emissions in white dwarf systems.

## Key findings

- BL luminosity depends on system parameters
- Spectral analysis helps distinguish between models with similar luminosities
- Method developed to infer system properties from boundary layer radiation

## Abstract

We perform numerical hydrodynamical simulations in order to calculate the luminosity and the spectrum of the BL and its dependence on parameters like the mass, rotation rate or mass accretion rate of the central white dwarf (WD). Therefore, we treat the problem in the one-dimensional, radial slim disk approximation. We employ a classical $\alpha$-viscosity to account for the turbulence and include cooling from the disk surfaces as well as radial radiation transport. To account for the high temperatures in BLs around WDs, we also consider the radiation energy in a one-temperature approximation. We find that 1D models of the BL are well suited if one is interested in the radiation characteristics of the BL. The BL luminosity directly depends on the varied parameters which makes it possible to draw conclusions about real systems by comparing observations with our synthetic models. Ambiguities concerning different models with identical luminosities can be mitigated by regarding the emitted spectrum. We therefore present a method to gain information about a system by probing the radiation of the BL.