Observation of light echoes around very young stars

J. L. ORTIZ, B. E. K. SUGERMAN, I. DE LA CUEVA, P. SANTOS-SANZ, R. DUFFARD, R. GIL-HUTTON, M. MELITA AND N. MORALES

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2010 vol. 519 p. 7 - 14

0004-6361

Aims. The goal of the paper is to present new results on light echoes from young stellar objects.Methods. Broad band CCD images were obtained over three months at one-to-two week intervals for the field of NGC 6726, usingthe large field-of-view remotely-operated telescope on top of Cerro Burek.Results. We detected scattered light echoes around two young, low-amplitude, irregular variable stars. Observations revealed notjust one, but multiple light echoes from brightness pulses of the T Tauri star S CrA and the Herbig Ae/Be star R CrA. Analysis ofS CrA’s recurring echoes suggests that the star is located 138 ± 16 pc from Earth, making these the closest echoes ever detected. Theenvironment that scatters the stellar light from S CrA is compatible with an incomplete dust shell or an inclined torus some 10 000 AUin radius and containing ∼2 × 10−3 M of dust. The cause of such concentration at ∼10 000 AU from the star is unknown. It could bethe remnant of the envelope from which the star formed, but the distance of the cloud is remarkably similar to the nominal distanceof the Oort cloud to the Sun, leading us to also speculate that the dust (or ice) seen around S CrA might have the same origin as theSolar System Oort cloud.