Ultraviolet Photometry and Habitable Zones of Over 2700 Planet-Hosting Stars

TL;DR

This study analyzes UV photometry of over 2700 exoplanet host stars to assess habitability zones and stellar activity, revealing that few planets are in both habitable zones and UV habitable zones, with the Sun showing unique UV emission characteristics.

Contribution

It provides a comprehensive UV photometric catalog for over 2700 host stars and introduces methods to evaluate stellar activity and habitability zones using UV data.

Findings

Fewer than 100 exoplanets are within both habitable and UV habitable zones.

The FUV-NUV color better indicates stellar activity than traditional indices.

The Sun exhibits low FUV and moderate NUV emissions, highlighting its uniqueness.

Abstract

The ongoing discovery of exoplanets has sparked significant interest in finding suitable worlds that could potentially support life. Stellar ultraviolet (UV; 100-3000 \AA) radiation may play a crucial role in determining the habitability of their planets. In this paper, we conducted a detailed analysis of the UV photometry of over 2700 host stars with confirmed planets, using observational data from the GALEX and Swift UVOT missions. We performed aperture photometry on single-exposure images, and provided photometric catalogs that can be used to explore a wide range of scientific questions, such as stellar UV activity and planet habitability. By calculating the circumstellar habitable zone (CHZ) and UV habitable zone (UHZ), we found that fewer than 100 exoplanets fall within both of these zones, with the majority being gas giants. We also examined stellar activity based on their far-UV (FUV) and near-UV (NUV) emissions. We found the FUV$-$NUV color more effectively represents stellar activity compared to the $R^{\prime}_{\rm FUV}$ and $R^{\prime}_{\rm NUV}$ indices. The Sun's low FUV emission and moderate NUV emission highlight its uniqueness among (solar-like) stars.