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Musca - the heavenly fly.
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| The Extended Mid-Infrared Structure of the Circinus Galaxy
We present subarcsecond resolution mid-IR images of the Circinus galaxyat 8.74 and 18.33 μm. We resolve extended emission at bothwavelengths, extending ~2" from each side of the nucleus in anapproximate east-west direction. These extensions are spatiallycoincident with previously detected compact (~30 pc) V-shaped [O III]emission extending northwest of the nucleus as well as countercone [SiVI] emission, emission at these wavelengths interpreted as delineatingthe interface between inflowing material and the ionization cone. Wedetect no extended mid-IR emission associated with the structureresponsible for collimating the ionizing photons (i.e., obscuring torusor disk of material), limiting the flux density of the obscuringstructure to <=0.27 mJy or a diameter of <=0.20" (<=4 pc).
| 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
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| 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.
| Accurate positions for variable and suspected variable stars south of -67 deg
Improved positions for 950 confirmed variable and 368 suspected variablestars located south of -67 deg have been determined by measuring thefirst-epoch plates of the Yale-San Juan southern proper-motion survey.The new positions, referred to the system of the SRS, have an averagestandard error of 0.7 arcsec in both R.A. and Dec. Some of thedifferences with the coordinates quoted in the GCVS are as large as 1deg.
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