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Few Skewed Disks Found in First Closure-Phase Survey of Herbig Ae/Be Stars
Using the three-telescope IOTA interferometer on Mount Hopkins, wereport results from the first near-infrared (λ=1.65 μm)closure-phase survey of young stellar objects (YSOs). These closurephases allow us to unambiguously detect departures from centrosymmetry(i.e., skew) in the emission pattern from YSO disks on the scale of ~4mas, expected from generic ``flared disk'' models. Six of 14 targetsshowed small, yet statistically significant nonzero closure phases, withlargest values from the young binary system MWC 361-A and the(pre-main-sequence?) Be star HD 45677. Our observations are quitesensitive to the vertical structure of the inner disk, and we confrontthe predictions of the ``puffed-up inner wall'' models of Dullemond,Dominik, & Natta (DDN). Our data support disk models with curvedinner rims because the expected emission appears symmetricallydistributed around the star over a wide range of inclination angles. Incontrast, our results are incompatible with the models possessingvertical inner walls because they predict extreme skewness (i.e., largeclosure phases) from the near-IR disk emission that is not seen in ourdata. In addition, we also present the discovery of mysterious H-band``halos'' (~5%-10% of light on scales 0.01"-0.50") around a few objects,a preliminary ``parametric imaging'' study for HD 45677, and the firstastrometric orbit for the young binary MWC 361-A.
| On Two 1978 Novae - Nova Sagittarius 1978 = V3876-SAGITTARIUS and Nova Cygni 1978 = V1668-CYGNI
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Observation and Astrometry data
| Constellation: | Sagittarius |
| Right ascension: | 18h34m25.33s |
| Declination: | -19°47'04.8" |
| Apparent magnitude: | 7.18 |
| Distance: | 245.098 parsecs |
| Proper motion RA: | 32.7 |
| Proper motion Dec: | -18.9 |
| B-T magnitude: | 8.974 |
| V-T magnitude: | 7.329 |
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