# Fundamental parameters and infrared excesses of Tycho-Gaia stars

## TL;DR

This study calculates effective temperatures and luminosities for over 1.5 million Tycho-2 and Hipparcos stars using Gaia data, identifies stars with infrared excess, and demonstrates applications in astrophysical research.

## Contribution

It provides a large, homogeneous catalog of stellar parameters and infrared excesses, enhancing understanding of stellar properties and circumstellar environments.

## Key findings

- Infrared excess detected in 4256 stars, including AGB stars and young stellar objects.
- Uncertainties of +/-137 K in temperature and +/-35% in luminosity for Tycho-2 stars.
- Demonstrates applications in studying interstellar extinction, dust production, and stellar population gradients.

## Abstract

Effective temperatures and luminosities are calculated for 1,475,921 Tycho-2 and 107,145 Hipparcos stars, based on distances from Gaia Data Release 1. Parameters are derived by comparing multi-wavelength archival photometry to BT-Settl model atmospheres. The 1-sigma uncertainties for the Tycho-2 and Hipparcos stars are +/-137 K and +/-125 K in temperature and +/-35 per cent and +/-19 per cent in luminosity. The luminosity uncertainty is dominated by that of the Gaia parallax. Evidence for infrared excess between 4.6 and 25 microns is found for 4256 stars, of which 1883 are strong candidates. These include asymptotic giant branch (AGB) stars, Cepheids, Herbig Ae/Be stars, young stellar objects, and other sources. We briefly demonstrate the capabilities of this dataset by exploring local interstellar extinction, the onset of dust production in AGB stars, the age and metallicity gradients of the solar neighbourhood and structure within the Gould Belt. We close by discussing the potential impact of future Gaia data releases.