Bram ACKE : Institute for Astronomy, KU Leuven
A giant planet orbiting the Herbig Be star HD 100546? Unexpected evidence from the [O I] 6300A emission line
The dust disk around the Herbig Be star HD 100546 is one of the oldest circumstellar disks known. Its longevity exceeds 10 Myr. To explain the spectral energy distribution of the source, Bouwman et al. (2003) suggested that the dust disk is not a continuous flared disk, but that a gap is present. They argue that this gap is planet-induced. The presence of the gap was later confirmed by different authors (Liu et al. 2003, Grady et al. 2005). In 2005, we have published a paper concerning the forbidden oxygen lines at 6300 and 6363A in the spectra of a sample of Herbig Ae/Be stars (Acke, van den Ancker & Dullemond 2005). We argue that these features emanate from the surface layers of the flared circumstellar disk. The talk I present here is based on Acke & van den Ancker (A&A accepted). We focus on the [OI] 6300A line in the spectrum of HD 100546. For the first time, the effect of the hypothetical planet orbiting this star on the circumstellar gas is examined. Using the technique of spectro-astrometry, we deduce the spectral and spatial(!) structure of the [OI] emission region from high-resolution UVES spectra. Furthermore, we discuss long-term temporal variations in the spectral profile of the emission line. We conclude that the spectral, spatial land temporal information on HD 100546 evidence the presence of a massive companion. Based on the characteristics of the [OI] line, we estimate its mass and orbital distance to the star to be 20 Jupiter masses and 6.5 AU respectively. If confirmed, these observations could point to the existence of an object straddling the line between giant planet and brown dwarf in a system as young as 10 million years.Last modified: Sun Jul 9 17:21:46 2006