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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
| Bispectrum speckle interferometry of the Red Rectangle: Diffraction-limited near-infrared images reconstructed from Keck telescope speckle data
We present new near-infrared (2.1-3.3 mu m) images of the RedRectangle with unprecedented diffraction-limited angularresolutions of 46-68 mas; 4 times higher than that of the Hubble spacetelescope and almost a factor of two improvement over the previous 6 mSAO telecope speckle images presented by Men'shchikov et al.(\cite{Men'shchikov_etal1998}). The new images, which were reconstructedfrom Keck telescope speckle data using the bispectrum speckleinterferometry method, clearly show two bright lobes above and below theoptically thick dark lane obscuring the central binary. X-shaped spikes,thought to trace the surface of a biconical flow, change the intensitydistribution of the bright lobes, making them appear broadened or withan east-west double-peak in images with the highest resolution. Thestriking biconical appearance of the Red Rectangle ispreserved on scales from 50 mas to 1 arcmin and from the visible (red)to at least 10 mu m, implying that large grains of at least severalmicrons in size dominate scattering. The new images supplement previous76 mas resolution speckle reconstructions at shorter wavelengths of0.6-0.8 mu m (Osterbart et al. \cite{Osterbart_etal1997}) and 0.7-2.2 mum (Men'shchikov et al. \cite{Men'shchikov_etal1998}), allowing a moredetailed analysis of the famous bipolar nebula. The intensitydistribution of the images is inconsistent with a flat disk geometryfrequently used to model the bipolar nebulae. Instead, a geometricallythick torus-like density distribution with bipolar conical cavities ispreferred. The extent of the bright lobes indicates that the dense torushas a diameter of >~ 100 AU, for an assumed distance of 330 pc. Thistorus may be the outer reaches of a flared thick disk tapering inwardsto the central star, however such a density enhancement on the midplaneis not strictly required to explain the narrow dark lane obscuring thecentral stars.
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