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Subaru Near-Infrared Imaging of Herbig Ae Stars
We report results of H-band (? = 1.65?m) imaging observationsof young intermediate-mass stars using the Subaru 8.2-m Telescope withthe adaptive optics AO36 and the infrared coronagraph CIAO. The targetsconsist of 16 Herbig Ae/Be stars (15 Herbig Ae stars and one Herbig Bestar) and four additional main-sequence stars with infrared excesses.Five protoplanetary disks have been spatially resolved around the HerbigAe stars with ages of 2-8 Myr. The resolved disks have outer radii ofseveral 100 AU, and their surface brightnesses range from 10 magarcsec-2 to 18 mag arcsec-2. The images revealvarious morphologies in optically thick disks: spiral arms around ABAur, a banana-split structure with an outer arm for HD 142527, a compactcircumprimary disk of HD 150193, a faint discontinuous ring around HD163296, and an unstructured face-on disk of HD 169142. The detection ofan optically thick disk in scattered light implies that it is verticallyflared, and intercepts stellar light at least in the outer region wherethose images were obtained. However, the surface brightnessdistribution, the resolved structure, and other observationalcharacteristics suggest that the disks are unlikely to be continuouslyflared young disks with small grains well mixed with gas. The detectionrate and the disk brightness do not correlate with the stellar age andthe disk mass, but there is a tendency that the brightest disks arestill surrounded by long-lived envelopes (AB Aur, HD 100546, HD 142527).The significant diversity of the disk structure can be attributed to themultiplicity and the initial condition of the local star-formingenvironments. The detections of companion candidates around our targetedstars are also reported.
| Far-ultraviolet stellar photometry: A field in Orion
Far-ultraviolet photometry for 625 objects in Orion is presented. Thesedata were extracted from electrographic camera images obtained duringsounding rocket flights in 1975 and 1982. The 1975 images were centeredclose to the belt of Orion while the 1982 images were centeredapproximately 9 deg further north. One hundred and fifty stars fell inthe overlapping region and were observed with both cameras. Sixty-eightpercent of the objects were tentatively identified with known starsusing the SIMBAD database while another 24% are blends of objects tooclose together to separate with our resolution. As in previous studies,the majority of the identified ultraviolet sources are early-type stars.However, there are a significant number for which no such identificationwas possible, and we suggest that these are interesting objects whichshould be further investigated. Seven stars were found which were brightin the ultraviolet but faint in the visible. We suggest that some ofthese are nearby white dwarfs.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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