Hot circumstellar material resolved around beta Pic with VLTI/PIONIER

TL;DR

This study used VLTI/PIONIER interferometry to resolve and analyze the near-infrared circumstellar environment of beta Pic, detecting a stable excess likely caused by hot dust or scattering, and accurately measuring the star's angular diameter.

Contribution

First high-precision interferometric detection of near-infrared excess around beta Pic, revealing circumstellar dust or scattering and providing an accurate stellar diameter measurement.

Findings

Detected 1.37% near-infrared excess around beta Pic.

Measured stellar angular diameter as 0.736 mas with high accuracy.

Found the excess to be stable over one year and weakly variable across H band.

Abstract

We aim at resolving the circumstellar environment around beta Pic in the near-infrared in order to study the inner planetary system (< 200 mas, i.e., ~4 AU). Precise interferometric fringe visibility measurements were obtained over seven spectral channels dispersed across the H band with the four-telescope VLTI/PIONIER interferometer. Thorough analysis of interferometric data was performed to measure the stellar angular diameter and to search for circumstellar material. We detected near-infrared circumstellar emission around beta Pic that accounts for 1.37% +/- 0.16% of the near-infrared stellar flux and that is located within the field-of-view of PIONIER (i.e., ~200 mas in radius). The flux ratio between this excess and the photosphere emission is shown to be stable over a period of 1 year and to vary only weakly across the H band, suggesting that the source is either very hot (> 1500 K) or dominated by the scattering of the stellar flux. In addition, we derived the limb-darkened angular diameter of beta Pic with an unprecedented accuracy (theta_LD= 0.736 +/- 0.019 mas). The presence of a small H-band excess originating in the vicinity of beta Pic is revealed for the first time thanks to the high-precision visibilities enabled by VLTI/PIONIER. This excess emission is likely due to the scattering of stellar light by circumstellar dust and/or the thermal emission from a yet unknown population of hot dust, although hot gas emitting in the continuum cannot be firmly excluded.