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Session 19 - Solar & Planetary Systems.
Display session, Monday, January 13
We mapped 60 \mum emission around 5 Vega-type systems. We utilized the PHT-C100 3\times3-pixel far-infrared camera on-board ISO, in the P32 microscanning dedicated mapping mode. The maps are centered on the stars and span 6'15''\times5'45'' (RA\timesDEC), at a spatial resolution of 15''. The maps of 3 sources (\alpha CrB, \sigma Her, and \alpha CenB) do not show any evidence of extended emission when compared to a model point-spread function obtained from a similar map of \alpha Boo. The map of \gamma Oph possibly shows extended emission \sim 30'' from the star, slightly above the background noise (\sim 4 MJy/sr). The map of \alpha PsA shows extended emission features \sim 30--80'' from the star. The extended emission peak brightness in \alpha PsA, after background subtraction, is \sim 13 MJy/sr, or \sim 4\sigma, above the background noise.
The S/N of our mapping observations is not high but as a preliminary result we estimate some physical parameters of the 60 \mum emitting dust around \alpha PsA. The innermost \sim 30'' or \sim 210 AU from the star are relatively dust-depleted. The dust is found between \sim 210 AU and \sim 560 AU from the star, with peak 60 \mum emission located at \sim 320 AU. We take the latter as a characteristic location of the emitting dust. This location, together with a characteristic IRAS temperature of 72 K (Backman amp; Paresce 1993, Protostars and Planets III, ed.\ Levy amp; Lunine, 1253), suggests the observed dust grains are \sim 1.5 \mum in size. The mass of these grains emitting the total extended emission of \sim 11.9 Jy across \sim 3.4 \times 10^3 arcsec^2 is \sim 3 \times 10^-3 M_øplus.
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