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New Debris Disk Candidates Around 49 Nearby Stars
We present 49 new candidate debris disks that were detected aroundnearby stars with the Spitzer Space Telescope using the MultibandImaging Photometer (MIPS) at 24 μm (MIPS24) and 70 μm (MIPS70).The survey sample was composed of stars within 25 pc of the Sun thatwere not previously observed by any other MIPS survey. Only stars with V< 9 were selected, corresponding to spectral types earlier than M0.MIPS24 integration times were chosen to detect the stellar photosphereat 10σ levels or better. MIPS70 observations were designed todetect excess infrared emission from any star in the MIPS70 sample witha disk as luminous at that around epsilon Eridani. The resulting sampleincluded over 436 nearby stars that were observed with both MIPS24 andMIPS70, plus an additional 198 observed only with MIPS24. Debris diskcandidates were defined as targets where excess emission was detected at3σ levels or greater, and the ratio of observed flux density toexpected photosphere emission was three standard deviations or moreabove the mean value for the sample. The detection rate implied by theresulting 29 MIPS24 candidates is 4.6%. A detection rate of 4.8% isimplied by 21 MIPS70 candidates. The distribution of spectral types forstars identified as candidates resembles that of the general sample andyields strong evidence that debris-disk occurrence does not decrease forK dwarfs. Modeling of non-uniform sensitivity in the sample is requiredto interpret quantitative estimates of the overall detection frequencyand will be presented in a future work.
| The main sequence from F to K stars of the solar neighbourhood in SDSS colours
For an understanding of Galactic stellar populations in the SDSS filtersystem well defined stellar samples are needed. The nearby stars providea complete stellar sample representative for the thin disc population.We compare the filter transformations of different authors applied tothe main sequence stars from F to K dwarfs to SDSS filter system anddiscuss the properties of the main sequence. The location of the meanmain sequence in colour-magnitude diagrams is very sensitive tosystematic differences in the filter transformation. A comparison withfiducial sequences of star clusters observed in g', r', and i' show goodagreement. Theoretical isochrones from Padua and from Dartmouth havestill some problems, especially in the (r-i) colours.
| 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.
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| Dwarf K and M stars in the southern hemisphere.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..486U&db_key=AST
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