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Discovery of Close Companions to the Nearby Young Stars HD 199143 and HD 358623
Young stellar systems in the solar neighborhood provide valuablelaboratories for detailed studies of star and planet formation. Thebright F8 V star HD 199143 and the Li-rich late-type emission-line starHD 358623 are among the nearest young stars identified to date and maybe members of a young association in Capricornus. We presenthigh-resolution near-infrared images of these two sources, obtainedusing the adaptive optics system on the 3.6 m telescope at the EuropeanSouthern Observatory in La Silla, Chile. Our observations reveal thatboth are, in fact, close binary systems. The newly discovered companionat a separation of ~1" may account for the unusual characteristics of HD199143-rapid rotation, emission lines, ultraviolet variability, andexcess infrared emission-recently discussed by van den Ancker andcoworkers. HD 199143 may be a rare example of a close binary with only acircumsecondary disk. With the detection of a ~2" companion, HD 358623is now possibly one of the closest known T Tauri binaries. Both binarysystems are prime targets for follow-up spectroscopic and astrometricobservations. Based on observations collected at the European SouthernObservatory, Chile.
| Photoelectric observations of lunar occultations. XIII
Occultation observations made with the 0.76 m reflector at McDonaldObservatory are presented, for 319 events occurring between Jan. 15,1981 and Feb. 7, 1982. One table reports timings, and a second recordsobservations of 16 double stars, in particular, Nu Gem observationsreveal that the two close components are similar in color. This allowsan estimation of individual visible magnitudes (near 4.60 and 5.32)suggesting that the secondary is a late B-type main-sequence star. SAO158929 observations reveal systematic differences in angular diametervalues. Of the 16 observed double stars, 9 appear to be new discoveries,including SAO 93067, SAO 94595, and SAO 98770. A third table gives fullydarkened angular diameters for the stars SAO 158929, SAO 77516 Y Tau,and SAO 119035 Nu Vir.
| Estimation of spectral classifications for bright southern stars with interesting Stromgren indices
This paper investigates the degree of success with which uvby photometrycan be applied to predict spectral classifications for 947 A, F, and Gstars brighter than an apparent magnitude of 8.3 and with four-colorindices indicating some kind of interesting, unusual, or peculiarspectrum. One or several possible spectral classifications are estimatedfor each star from photometry alone, double stars are distinguished, andthe estimates are compared with published classifications. The resultsshow that the framework provided by uvby photometry can be extended toinclude most G and K stars, reddened stars, peculiar stars, and certaintypes of double star.
| Observations of occultations of stars by the moon
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...13..395H&db_key=AST
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Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Oglak |
| Sað Açýklýk: | 20h48m13.68s |
| Yükselim: | -19°15'37.0" |
| Görünürdeki Parlaklýk: | 6.807 |
| Uzaklýk: | 85.911 parsek |
| özdevim Sað Açýklýk: | 35.8 |
| özdevim Yükselim: | -22.5 |
| B-T magnitude: | 7.287 |
| V-T magnitude: | 6.847 |
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