Planetary system around Vega

Abstract

We applied our earlier numerical method to compute the thermal emission from a dusty resonant structure around Vega and compared the new observational evidence for a ring arc at 95 AU near Vega with our modeling. Our high resolution simulations indicate that Vega may have an outerm ost planet at a distance of 90-100 AU with coordinates near 18 35&#39;16.25&#34; (right ascension, B1950) and 38 44&#39;15&#34; (declination). Another symmetrical position, 18 35&#39;14.75&#34; and 38 44&#39;32.5&#34;, of the planet is also possible. Radii of the observed clumps (and planet&#39;s orbital radius) may be smaller, e.g. ~60-75 AU. In this case the planet stays approximately on the line between the two possible positions above. From our modeling we make following conclusions: 1.Dust clumps rotate around Vega exactly wi th the planet orbital speed, 0.6-1.2 deg/year, as function of orbital radius of parent planet. 2. Orbital radius of the planet is approximately the same as the orbital radius of clumps (90-100 AU from observation by Koerner, Sargent & Ostroff, 2001 or 60-75 AU from observation by Wilner, Holman, Ho & Kuchner, 2002). 3. The most dense clump is ahead of the planet in the direction of the orbital motion. 4. The orbit of the planet may be circular or with a small eccentricity. 5. Absence of dust i n the inner part of Vega planetary system is a signature of inner planet(s) with orbital radii <50-60 AU.