Dust-Scattered Ultraviolet Halos around Bright Stars

TL;DR

This study reports the discovery of ultraviolet halos around bright stars caused by dust scattering, providing new insights into interstellar dust properties and their scattering behavior at small angles.

Contribution

It introduces the first observations of UV halos around bright stars and constrains dust scattering parameters, advancing understanding of interstellar dust scattering properties.

Findings

Ultraviolet halos extend up to 5 degrees around bright stars.

Constraints on dust scattering phase function asymmetry factor g.

Limits on dust albedo in FUV and NUV bands.

Abstract

We have discovered ultraviolet halos extending as far as 5{\deg} around four (of six) bright UV stars using data from the GALEX satellite. These halos are due to the scattering of the starlight from nearby thin, foreground dust clouds. We have placed limits of 0.58 $\pm$ 0.12 and 0.72 $\pm$ 0.06 on the phase function asymmetry factor (g) and limits on the albedo of 0.10 $\pm$ 0.05 and 0.26 $\pm$ 0.10 in the FUV (1521 {\AA}) and NUV (2320 {\AA}) bands, respectively. We suggest that these halos are a common feature around bright stars and may be used to explore the scattering function of interstellar grains at small angles.