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The Keck Aperture-masking Experiment: Near-Infrared Sizes of Dusty Wolf-Rayet Stars
We report the results of a high angular resolution near-infrared surveyof dusty Wolf-Rayet stars using the Keck I Telescope, including newmultiwavelength images of the pinwheel nebulae WR 98a, WR 104, and WR112. Angular sizes were measured for an additional eight dustyWolf-Rayet stars using aperture-masking interferometry, allowing us toprobe characteristic sizes down to ~20 mas (~40 AU for typical sources).With angular sizes and specific fluxes, we can directly measure thewavelength-dependent surface brightness and size relations for oursample. We discovered tight correlations of these properties within oursample that could not be explained by simple spherically symmetric dustshells or even the more realistic ``pinwheel nebula''(three-dimensional) radiative transfer model, when using Zubko's opticalconstants. While the tightly correlated surface brightness relations weuncovered offer compelling indirect evidence of a shared and distinctivedust shell geometry among our sample, long-baseline interferometersshould target the marginally resolved objects in our sample in order toconclusively establish the presence or absence of the putativeunderlying colliding-wind binaries thought to produce the dust shellsaround WC Wolf-Rayet stars.
| Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/997
| Classification and Identification of IRAS Sources with Low-Resolution Spectra
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
| Search for stars with intrinsic polarization
Results of polarimetric observations of 55 late-type stars arepresented. Twenty of these stars were found to have appreciablepolarization. The dependence of the degree of polarization on wavelengthis given. It is considered very probable that the polarizations of thestars SAO 141881, 141898, and 160413 are intrinsic.
| The Distribution of the BD M-Type Stars Along the Galactic Equator.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958ApJ...128..510N&db_key=AST
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Observation and Astrometry data
| Constellation: | Aquila |
| Right ascension: | 18h43m37.37s |
| Declination: | -01°33'32.5" |
| Apparent magnitude: | 7.217 |
| Distance: | 265.957 parsecs |
| Proper motion RA: | 6.3 |
| Proper motion Dec: | -2.8 |
| B-T magnitude: | 9.674 |
| V-T magnitude: | 7.42 |
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