# The Influences of Forming Companions on the Spectral Energy Distributions of Stars with Circumstellar Discs

## TL;DR

This study explores how brown dwarf companions embedded in protoplanetary discs influence their spectral energy distributions, revealing potential signatures for detection and insights into disc-companion interactions.

## Contribution

It presents a novel simulation approach linking gap features in SEDs to brown dwarf companions within protoplanetary discs, enabling detection of smaller companions at closer distances.

## Key findings

- Presence of a gap causes an additional minimum in the SED at 10-100 μm.
- Detectable signatures of companions as small as 3 M_J within 10 AU.
- Disc parameters significantly affect the SED differences caused by companions.

## Abstract

We study a possibility to detect signatures of brown dwarf companions in a circumstellar disc based on spectral energy distributions (SED). We present the results of SED simulations for a system with a 0.8 $M_{\odot}$ central object and a companion with a mass of 30 $M_J$ embedded in a typical protoplanetary disc. We use a solution to the one-dimensional radiative transfer equation to calculate the protoplanetary disc flux density and assume, that the companion moves along a circular orbit and clears a gap. The width of the gap is assumed to be the diameter of the brown dwarf Hill sphere. Our modelling shows that the presence of such a gap can initiate an additional minimum in the SED profile of a protoplanetary disc at $\lambda = 10 - 100$ $\mu$m. We show that the depth of this minimum and the wavelength of the maximum difference between the SEDs of the system with and without a companion are related to the companion mass and its proximity to the star. We found that it is possible to detect signatures of the companion when it is located within 10 AU, even when it is as small as 3 $M_J$. We also analyse how the disc parameters (the inner radius and the temperature profile) change the maximum difference between the SEDs for the same systems with and without a companion. The SED of a protostellar disc with a massive fragment might have a similar double peaked profile to the SED of a more evolved disc that contains a gap. However, in this case, it will be caused by the presence of an additional maximum at shorter wavelengths and will be similar only when the massive fragment is relatively cold ($\sim$400 K).