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AKARI's infrared view on nearby stars. Using AKARI infrared camera all-sky survey, 2MASS, and Hipparcos catalogs
Context. The AKARI, a Japanese infrared space mission, has performed anAll-Sky Survey in six infrared-bands from 9 to 180 ?m with higherspatial resolutions and better sensitivities than IRAS. Aims: Weinvestigate the mid-infrared (9 and 18 ?m) point source catalog (PSC)obtained with the infrared camera (IRC) onboard AKARI, in order tounderstand the infrared nature of the known objects and to identifypreviously unknown objects. Methods: Color-color diagramsand a color-magnitude diagram were plotted with the AKARI-IRC PSCand other available all-sky survey catalogs. We combined the Hipparcosastrometric catalog and the 2MASS all-sky survey catalog with theAKARI-IRC PSC. We furthermore searched literature and SIMBADastronomical database for object types, spectral types, and luminosityclasses. We identified the locations of representative stars and objectson the color-magnitude and color-color diagram schemes. Theproperties of unclassified sources can be inferred from their locationson these diagrams. Results: We found that the (B-V) vs.(V-S9W) color-color diagram is useful for identifying thestars with infrared excess emerged from circumstellar envelopes ordisks. Be stars with infrared excess are separated well from other typesof stars in this diagram. Whereas (J-L18W) vs. (S9W-L18W)diagram is a powerful tool for classifying several object types.Carbon-rich asymptotic giant branch (AGB) stars and OH/IR stars formdistinct sequences in this color-color diagram. Young stellarobjects (YSOs), pre-main sequence (PMS) stars, post-AGB stars, andplanetary nebulae (PNe) have the largest mid-infrared color excess andcan be identified in the infrared catalog. Finally, we plot the L18W vs.(S9W-L18W) color-magnitude diagram, using the AKARI data togetherwith Hipparcos parallaxes. This diagram can be used to identify low-massYSOs and AGB stars. We found that this diagram is comparable to the [24]vs. ([8.0]-[24]) diagram of Large Magellanic Cloud sources usingthe Spitzer Space Telescope data. Our understanding of Galactic objectswill be used to interpret color-magnitude diagram of stellar populationsin the nearby galaxies that Spitzer Space Telescope observed. Conclusions: Our study of the AKARI color-color andcolor-magnitude diagrams will be used to explore properties ofunknown objects in the future. In addition, our analysis highlights afuture key project to understand stellar evolution with a circumstellarenvelope, once the forthcoming astronometrical data with GAIA areavailable.Catalog (full Tables 3 and 4) are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/514/A2
| Infrared photometry and evolution of mass-losing AGB stars. II. Luminosity and colors of MS and S stars
Context: Asymptotic giant branch (AGB) phases mark the end of theevolution for low- and intermediate-mass stars. Our understanding of themechanisms through which they eject the envelope and our assessment oftheir contribution to the mass return to the interstellar medium and tothe chemical evolution of Galaxies are hampered by poor knowledge oftheir luminosities and mass loss rates, both for C-rich and for O-richsources. Aims: We plan to establish criteria permitting a morequantitative determination of luminosities (and subsequently of massloss rates) for the various types of AGB stars on the basis of infraredfluxes. In this paper, in particular, we concentrate on O-rich ands-element-rich MS, S stars and include a small sample of SC stars. Methods: We reanalyze the absolute bolometric magnitudes and colors ofMS, S, SC stars on the basis of a sample of intrinsic (single) andextrinsic (binary) long period variables. We derive bolometriccorrections as a function of near- and mid-infrared colors, adopting asreferences a group of stars for which the spectral energy distributioncould be reconstructed in detail over a large wavelength range. Wedetermine the absolute HR diagrams, and compare luminosities and colorsof S-type giants with those, previously derived, of C-rich AGB stars.Luminosity estimates are also verified on the basis of existingperiod-luminosity relations valid for O-rich Miras. Results: S starbolometric luminosities are almost indistinguishable from those ofC-rich AGB stars. On the contrary, their circumstellar envelopes arethinner and less opaque. Despite this last property the IR wavelengthsremain dominant, with the bluest stars having their maximum emission inthe H or K(short) bands. Near-to-mid infrared color differences are inany case smaller than for C stars. Based on period-luminosity relationsfor O-rich Miras and on Magnitude-color relations for the same variableswe show how approximate distances (hence intrinsic parameters) forsources of so far unknown parallax can be inferred. We argue that mostof the sources have a rather small mass (<2 Mȯ);dredge-up might then be not effective enough to let the C/O ratio exceedunity.Tables [see full textsee full textsee full textsee full textsee fulltextsee full text]-[see full textsee full textsee full textsee fulltextsee full textsee full text] are only available in electronic form athttp://www.aanda.org Tables 11 and 12 are only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/488/675
| The HIPPARCOS Hertzsprung-Russell diagram of S stars: probing nucleosynthesis and dredge-up
HIPPARCOS trigonometrical parallaxes make it possible to compare thelocation of Tc-rich and Tc-poor S stars in the Hertzsprung-Russell (HR)diagram: Tc-rich S stars are found to be cooler and intrinsicallybrighter than Tc-poor S stars. The comparison with the Genevaevolutionary tracks reveals that the line marking the onset of thermalpulses on the asymptotic giant branch (AGB) matches well the observedlimit between Tc-poor and Tc-rich S stars. Tc-rich S stars are, asexpected, identified with thermally-pulsing AGB stars of low andintermediate masses, whereas Tc-poor S stars comprise mostly low-massstars (with the exception of 57 Peg) located either on the red giantbranch or on the early AGB. Like barium stars, Tc-poor S stars are knownto belong exclusively to binary systems, and their location in the HRdiagram is consistent with the average mass of 1.6+/-0.2 Msb ȯderived from their orbital mass-function distribution (Jorissen et al.1997, A&A, submitted). A comparison with the S stars identified inthe Magellanic Clouds and in the Fornax dwarf elliptical galaxy revealsthat they have luminosities similar to the galactic Tc-rich S stars.However, most of the surveys of S stars in the external systems did notreach the lower luminosities at which galactic Tc-poor S stars arefound. The deep Westerlund survey of carbon stars in the SMC uncovered afamily of faint carbon stars that may be the analogues of thelow-luminosity, galactic Tc-poor S stars. Based on data from theHIPPARCOS astrometry satellite
| A General Catalogue of Galactic S-Stars - ED.2
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| A general catalogue of S stars.
Not Available
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