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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
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| ASCA Observations of Type 2 Seyfert Galaxies. I. Data Analysis Results
We present ASCA spatial, temporal, and spectral data for a sample of 26observations of 25 type 2 active galactic nuclei (AGNs), composed of 17Seyfert 2 galaxies and eight narrow emission line galaxies (NELGs).Twenty-four of the 25 sources were detected. The ASCA images aregenerally consistent with emission from point sources at energies above~3 keV. We use archival ROSAT data to examine each field at high spatialresolution and to check for the presence of sources that wouldcontaminate the ASCA data. Of the five sources bright enough for 128 stemporal analysis, three are variable at >99% confidence, withcharacteristics consistent with those observed in Seyfert 1 galaxies.Analysis on a timescale of 5760 s reveals six sources variable at>99% confidence, and comparison with previous X-ray results showsmost of the sample to be variable in hard X-ray flux on timescales ofyears. Simple continuum models are fitted to the sample spectra tocharacterize the variety of spectral forms and hence to determine thefundamental nature of the X-ray spectrum of each source. No singlespectral model provides an adequate fit to all the sample sources.Thirty-six percent of the sample cannot be adequately fitted by any ofour test models (all rejected at >95% confidence). Approximately halfof the sample have an iron K alpha line with an equivalent widthconsistent with an origin in the line-of-sight absorber; the remaininglines must be produced in material out of the line of sight. Absorbingcolumns up to 1024 atoms cm-2 are detected, and even larger columns areinferred for some sources. The mean underlying hard X-ray power-lawindex is Gamma ~ 2. Many X-ray emission lines were detected at highlevels of confidence. The iron K-shell regime is dominated by emissionfrom "neutral" material. Many data sets also show evidence forcomplexity in the iron K alpha profile, which may be interpreted asevidence for broad-line profiles, including flux both redward andblueward of the line peak, and/or for the existence of hydrogen-like andhelium-like iron K lines. Hydrogen-like and helium-like lines aredetected from Fe, Ne, Si, S, and Ar in addition to Mg lines. Whilealmost half of the sample have an estimated starburst contribution of>30% in the 0.5-4.5 keV bandpass, the soft X-ray emission lines arenot solely associated with a strong starburst component.
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Osservazione e dati astrometrici
| Costellazione: | Colomba |
| Ascensione retta: | 05h07m06.17s |
| Declinazione: | -37°42'01.6" |
| Magnitudine apparente: | 8.594 |
| Distanza: | 1000 parsec |
| Moto proprio RA: | -0.8 |
| Moto proprio Dec: | 1.8 |
| B-T magnitude: | 10.927 |
| V-T magnitude: | 8.787 |
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