Discovery of Reflection Nebulosity around Five Vega-like Stars

Coronagraphic optical observations of six Vega-like stars reveal reflection nebulosities, five of which were previously unknown. The nebulosities illuminated by HD 4881, HD 23362, HD 23680, HD 26676, and HD 49662 resemble that of the Pleiades, indicating an interstellar origin for dust grains. The reflection nebulosity around HD 123160 has a double-arm morphology, but no disklike feature is seen as close as 25 from the star in K-band adaptive optics data. We demonstrate that a uniform density dust cloud surrounding HD 23362, HD 23680, and HD 123160 can account for the observed 12-100 μm spectral energy distributions. For HD 4881, HD 26676, and HD 49662, an additional emission source, such as from a circumstellar disk or nonequilibrium grain heating, is required to fit the 12-25 μm data. These results indicate that in some cases, particularly for Vega-like stars located beyond the Local Bubble (>100 pc), the dust responsible for excess thermal emission may originate from the interstellar medium rather than from a planetary debris system.

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