Hot circumstellar material resolved around beta Pic with VLTI/PIONIER

D. Defrère , J. Lebreton (1) , J. -B. Le Bouquin (1) , A. -M. Lagrange (1) , O. Absil (2) , J. -C. Augereau (1) , J. -P. Berger (3) , E. Di Folco (4) , S. Ertel , J. Kluska (1) , G. Montagnier (3) , R. Millan-Gabet (5) , W. Traub (6) , G. Zins (1)

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
2 Université de Liège
3 ESO - European Southern Observatory
4 AMOR 2012
5 NExScI - NASA ExoPlanet Science Institute
6 JPL - Jet Propulsion Laboratory

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.

Domaines: Astrophysique stellaire et solaire [astro-ph.SR]; Astrophysique stellaire et solaire [astro-ph.SR]; Planétologie et astrophysique de la terre [astro-ph.EP]; Planétologie et astrophysique de la terre [astro-ph.EP]

D. Defrère, J. Lebreton, J. -B. Le Bouquin, A. -M. Lagrange, O. Absil, et al.. Hot circumstellar material resolved around beta Pic with VLTI/PIONIER. Astronomy and Astrophysics - A&A, 2012, 546, pp.id.L9. ⟨10.1051/0004-6361/201220287⟩. ⟨hal-00832266⟩