Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993aas...183.4110b&link_type=abstract
American Astronomical Society, 183rd AAS Meeting, #41.10; Bulletin of the American Astronomical Society, Vol. 25, p.1353
Astronomy and Astrophysics
Astronomy
Scientific paper
To investigate the properties of a probable proto-planetary system, HD 45677, we acquired FUV spectra from the ASTRO-1 and IUE space missions of two Herbig Be stars: HD 45677 and HD 200775 -- young B2 Ve and B3 Ve stars with circumstellar disks. HD 45677 is viewed edge-on through the disk, while the HD 200775 sight-line apparently avoids the disk. After correcting for interstellar extinction and absorption toward both stars, we use HD 200775 as a comparison to HD 45677 in order to derive the HD 45677 disk absorption and to place an upper limit on the molecular hydrogen [N(H2) < 10(19) cm(-2) ] through the HD 45677 disk. We also measure N(HI) = 2.5 times 10(21) cm(-2) through the HD 45677 disk. Since the HD 45677 spectrum was taken during moderate disk extinction (AV ~ 0.7) between optical minimum and maximum of this variably-obscured star, the FUV dust absorption and gas densities characterize the general disk properties. Like the dense clumps observed by Sitko et al. (1993), the general disk dust absorption is almost flat up to about 1400 Angstroms, implying that the disk grains (RV ~ 6.2) are larger than those in molecular clouds (RV < 5.6). Moreover, the inferred fraction (f < 7.9 times 10(-3) ) of H-atoms in molecules compared to the total H-atoms is much less in the HD 45677 disk than in molecular clouds (f ~ 0.5). Because the disk FUV absorption rises from about 1400--1000 Angstroms with the same shape as that of hydrocarbon molecules, such as PAHs, there are large molecules in the disk. These hydrocarbons produce more absorption than predicted by the RV = 6.2 and can shield the outer parts of the proto-planetary disk from FUV radiation, though not enough to prevent the photodissociation of H2. Thus, both the disk gas and dust have evolved since the formation of HD 45677 out of the Galactic medium, becoming more atomic and larger in the general disk around HD 45677.
Bjorkman Karen
Brown Tim
Buss Richard H. Jr.
Grady Carol
Schulte-Ladbeck Regina
No associations
LandOfFree
The Growth of Solids and Radiation Shielding in the Young Stellar Disk of HD 45677 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Growth of Solids and Radiation Shielding in the Young Stellar Disk of HD 45677, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Growth of Solids and Radiation Shielding in the Young Stellar Disk of HD 45677 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-778651