Astronomy and Astrophysics – Astronomy
Scientific paper
May 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998aas...192.1005j&link_type=abstract
American Astronomical Society, 192nd AAS Meeting, #10.05; Bulletin of the American Astronomical Society, Vol. 30, p.828
Astronomy and Astrophysics
Astronomy
Scientific paper
We report both ROSAT observations and ground-based 10.8 μm imaging of the wide binary HR 4796, which consists of a main sequence A-type star with a large amount of circumstellar dust, HR 4796A, and, at a separation of 7{\farcs}7, a pre-main sequence M-type companion, HR 4796B. From the ROSAT data, we find that the X-ray emission is centered on HR 4796B, with LX/LBol {~} 3 x 10(-4) . The 10.8 μm flux, which arises from HR 4796A, displays an excess over the photospheric emission of 0.08 {+/-} 0.02 Jy, a result consistent with the previous characterization of the emission from the circumstellar dust in the wavelength range 12 μm {<=} λ {<=} 100 μm as a 110 K black body. The {em Hipparcos} data can be used to argue that the three main sequence A type stars in the Bright Star Catalog with LIR/LBol > 10(-3) (HR 4796A, β Pic and 49 Cet) all have low luminosities for their colors. We suggest that very approximately 20% of all A-type stars pass through an early phase where they possess an amount of circumstellar dust comparable to that found around HR 4796A or β Pic. In order to explain the result that the grain emission can be approximated by a 110 K black body, we propose that the circumstellar grains are largely composed of ice particles with a typical radius near 100 μm and that they sublimate rapidly when they are closer than { ~ }35 AU to HR 4769A. This swarm of ice particles may be a proto-cometary cloud.
Jura Michael
Malkan Matthew
Pina Robert
Scott Fisher Robert
Telesco Charles
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