2012A&A...541A..71K

We analyze the surroundings of HD97300, one of two intermediate-mass stars in the ChamaeleonI star-forming region. The star is known to be surrounded by a conspicuous ring of polycyclic aromatic hydrocarbons (PAHs). We present infrared images taken with Herschel and Spitzer using 11 different broad-band filters between 3.6µm and 500µm. We compare the morphology of the emission using cuts along different position angles. We construct spectral energy distributions, which we compare to different dust models, and calculate dust temperatures. We also derive opacity maps and analyze the density structure of the environment of HD97300. We find that HD97300 has no infrared excess at or below 24µm, confirming its zero-age main-sequence nature. The morphology of the ring is very similar between 3.6µm and 24µm. The emission at these wavelengths is dominated by either PAH features or PAH continuum. At longer wavelengths, only the northwestern part of the ring is visible. A fit to the 100-500µm observations suggests that the emission is due to relatively warm (≃26K) dust. The temperature gradually decreases with increasing distance from the ring. We find a general decrease in the density from north to south, and an approximate 10% density increase in the northeastern part of the ring. Our results are consistent with the theory that the ring around HD97300 is essentially a bubble blown into the surrounding interstellar matter and heated by the star.