Adaptive Optics Observations of Vega: Eight Detected Sources and Upper Limits to Planetary-Mass Companions

Abstract

From adaptive optics observations with the Palomar 5-meter telescope we place upper limits on the masses of any planetary companions located between ~30-230 AU away from Vega, where our data are sensitive to depths ranging from H=12.5 mag to H=19.0 mag fainter than Vega itself. Our observations cover a plus-shaped area with two 25&#34;x57&#34; elements, excluding 7&#34;x7&#34; centered on the star. We have identified 2 double and 4 single point sources. These projected companions are 14.9-18.9 mag fainter than Vega, and if physically associated would have masses ranging from 4 to 35 Mjup and orbital radii 170-260 AU. Recent simulations of dusty rings around Vega predict the presence of a perturbing body with mass <2-3 Mjup and orbital radius ~40-100 AU, though more massive (~10 Mjup) planets cannot be excluded. None of the detected objects are this predicted planet. Based on a color-magnitude, spectroscopic, and proper motion analysis, all objects are consistent with being background sources. Given the glare of Vega, a 2 Mjup object near the expected orbital radii would not have been visible at the 5-sigma level in our data, though any >10 Mjup brown dwarf could have been seen at separation >80 AU.