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Two Micron All Sky Survey, Infrared Astronomical Satellite, and Midcourse Space Experiment Color Properties of Intrinsic and Extrinsic S Stars
We attempt to select new candidate intrinsic and extrinsic S stars inthe General Catalogue of Galactic S Stars (GCGSS) by combining data fromthe Two Micron All Sky Survey, the Infrared Astronomical Satellite, andthe Midcourse Space Experiment. Catalog entries are cross-identified,yielding 528 objects, out of which 29 are known extrinsic S stars and 31are known intrinsic S stars. Their color-color diagrams,(H-[12])-(K-[12]) and (K-[12])-(J-[25]), are drawn and used to identifya new sample of 147 extrinsic and 256 intrinsic S star candidates, whilethe nature of 65 stars remains identified. We infer that about 38%+/-10%of the GCGSS objects are of extrinsic type. Moreover, we think thatcolors such as J-[25] can be used to split off the two categories of Sstars, while single colors are not appropriate. The color-colordiagrams, such as (H-[12])-(K-[12]) and (K-[12])-(J-[25]), are proven tobe powerful tools for distinguishing the two kinds of S stars.
| Near-infrared observations of candidate extrinsic S stars
Photometric observations in the near infrared for 161 S stars, including18 Tc-rich (intrinsic) stars, 19 Tc-deficient (extrinsic) ones and 124candidates for Tc-deficient S stars, are presented in this paper. Basedon some further investigations into the infrared properties of bothTc-rich and Tc-deficient S stars, 104 candidates are identified as verylikely Tc-deficient S stars. The large number of infrared-selectedTc-deficient S stars provides a convenient way to study the physicalproperties and the evolutionary status of this species of S stars.
| A search for Technetium in semiregular variables
We searched for the lines of Tc in the spectra of Semiregular variables(SRVs) in the wavelength region from 4180 to 4300 Å using highresolution spectroscopy. Tc as an s-process element is produced on thethermally pulsing AGB and is therefore a good indicator for theevolutionary status of Semiregular variables. Combining our results withprevious investigations we get a database large enough for a statisticalstudy. Tc is not found in SRVs with periods below 100 days, spectraltypes earlier than M5 and photospheric IRAS colours. These objects are`blue' SRVs in the classification system of Kerschbaum & Hron(\cite{KH94}). Among the `red' SRVs (periods longer than 100 days) thefraction of stars showing Tc in their spectra is about 15 % with aprobably lower fraction among the stars with periods above 150 days.This is significantly lower than for the typical Miras. Taking intoaccount the probable conditions for the occurence of the third dredge-upand the expected behavior of the Tc abundance along an evolutionarytrack on the AGB, our results support an evolutionary scenario from`blue' SRVs (early AGB) to `red' SRVs (early TP-AGB) and on to longperiod Miras. Only the most massive (masses above 2M_ȯ) stars showTc during the SRV stage. The luminosities of the Tc-rich SRVs and Mirasare compatible with theoretical estimates of the minimum core massrequired for the third dredge-up. Based on observations collected at theEuropean Southern Observatory, La Silla, Chile (ESO No.54.E-0350), theGerman Spanish Astronomical Centre, Calar Alto, operated by theMax-Planck-Institute for Astronomy, Heidelberg, jointly with the SpanishNational Commission for Astronomy, and Kitt Peak National Observatory,USA.
| Spectra of Cool Stars in the J Band (1.0-1.3 μm) at Medium Resolution
A spectroscopic survey of 103 cool S-, C-, and M-type stars wasundertaken with the Kitt Peak cryogenic spectrograph on the 1.3 mtelescope to make a detailed search for new molecular bands in the1.0-1.3 μm J-band region. While the spectra have high signal-to-noiseratios and good repeatability, no strong new features were found. Higherresolution spectra of a small sample of representative stars observedwith the 4 m Fourier transform spectrometer were invoked in order toidentify the features in these spectra. With few exceptions, the detailsof these spectra are well understood. Laboratory spectra were obtainedto aid in the identification of some weak features. Spectral featuresfrom dominant lines of Ti, Fe, Al, Si, Mn, Na, and K, and molecularbands due to TiO, TiS, ZrO, ZrS, VO, H_2O, and CN, have been identifiedin the spectra. Several weak unidentified bands are found.
| Infrared study of the two categories of S stars
Photometric observations of 20 Tc-deficient and 24 Tc-rich S stars inthe near infrared are presented in this paper. With the IRAS data,infrared two color diagrams, IRAS low-resolution spectra and energydistributions are discussed to summarize the way to segregate Tc-richstars from Tc-deficient ones.
| 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.
| Proper motions, absolute magnitudes and spatial distribution of zirconium stars.
Not Available
| A catalogue of associations between IRAS sources and S stars.
Cross identifications between the General Catalogue of Galactic S Stars(GCGSS), the IRAS Point Source Catalogue (PSC), and the Guide StarCatalogue (GSC) are presented. The purpose of the present catalogue isi) to provide a clean sample of S stars with far-IR data, and ii) toprovide accurate GSC positions for S stars, superseding those listed inthe GCGSS. The IRAS colour-colour diagram and the galactic distributionof S stars associated with an IRAS source are presented. Several S starshaving extended images in at least one IRAS band have also beenidentified.
| Not Available
Not Available
| Circumstellar Properties of S Stars. I. Dust Features
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...416..769C&db_key=AST
| S stars: infrared colors, technetium, and binarity
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...271..463J&db_key=AST
| On the Infrared Properties of S-Stars with and Without Technetium
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...271..180G&db_key=AST
| Infrared Spectra and Circumstellar Emission of Late-Type Stars. III. S-Type Stars
Near-infrared photometry was carried out at the J, H, K, and L bands for73 S-type stars. The statistical characteristics of the infrared spectraand the circumstellar emission of S-type stars were examined usingnear-infrared photometric data, IRAS photometric data, and thelow-resolution spectra obtained by IRAS. The characteristics of thephotometric spectra of S-type stars were compared with those ofoxygen-rich stars and carbon stars. We found that MS and SC stars haveinfrared spectral characteristics similar to those of both oxygen-richstars and carbon stars, respectively. However, mild S, medium S, andstrong S stars were found to have a variety of spectral characteristicsin the infrared region. Correlations between the 10-mu m spectralfeatures and infrared photometric spectra were examined. It was foundthat S-type stars show a variety of spectral characteristics regardingboth the 10-mu m spectral feature and photometric spectra.
| S stars without technetium - The binary star connection
An exploratory survey of non-Mira MS and S star radial velocities andthe He I 10830 A triplet are used to test the assertion that S starswithout Tc are spectroscopic binaries, probably with white-dwarfcompanions. It is found that the He I 10830 A triplet is a prominentfeature of the spectra of S stars without Tc, but the He I line isundetectable in the spectra of most S stars without Tc. Also, whenradial-velocity variations attributable to orbital motion are detectedfor S stars without Tc, the variations have a higher frequency that thatof S stars with Tc. The results suggest that the S stars without Tc arespectroscopic binaries and are probably related to the G and K giantBarium stars.
| Mass loss from S stars
The mass-loss process in S stars is studied using 65 S stars from thelisting of Wing and Yorka (1977). The role of pulsations in themass-loss process is examined. It is detected that stars with largermass-loss rates have a greater amplitude of pulsations. The dust-to-gasratio for the S stars is estimated as 0.002 and the average mass-lossrate is about 6 x 10 to the -8th solar masses/yr. Some of the propertiesof the S stars, such as scale height, surface density, and lifetime, aremeasured. It is determined that scale height is 200 pc; the totalduration of the S star phase is greater than or equal to 30,000 yr; andthe stars inject 3 x 10 to the -6th solar masses/sq kpc yr into theinterstellar medium.
| Additional late-type stars with technetium
The results of a survey of 279 late-type giants and supergiants for thespectral lines of the radioactive element technetium (Tc I) at 4297,4262, and 4238 A are presented. The following conclusions are reached:(1) the presence of Tc correlates very strongly with the existence oflight variability; (2) evolutionary MS stars show Tc and spectroscopicMS stars do not show Tc; (3) single S stars show Tc; (4) SC stars showTc; (5) about 75 percent of the C stars show Tc; and (6) Ba II stars donot show Tc. The findings are compatible with predictions from stellarevolution theory.
| A General Catalogue of Galactic S-Stars - ED.2
Not Available
| Two newly discovered S stars in a list of faint red objects
A list of 103 faint red stars in a 0.7-square-degree area located nearNGC 6820/23 on the galactic plane in the constellation Vulpecula ispresented. The stars were chosen from Near Infrared Photographic SkySurvey visual and near-IR photographic pairs and were selected for theirvisual faintness as well as their red colors. Positions, approximatemagnitudes, and finding charts for these stars are presented. It isnoted that two members of the list, 1548C858 and 1548C869, have alreadybeen determined to be faint, pure S stars.
| A Search for S-Stars in the IRC and AFGL Catalogues
Seventeen unidentified sources contained in the 2jt JR Catalogue, andAFGL-AFGLS Catalogues have been tentatively indicated as S stars from acomparison with the General Catalogue of S stars. An analysis based onthe I - K and K - [4.2j.~] behavior has been performed for all thesources which have been found to be in common with all the abovementioned catalogues. The results lead to the conclusion that thepresence of circumstellar shells seems to be very unlike for theseobjects in spite of their evolutionary status which is intermediatebetween M and C type stars
| Spectroscopic study of the infrared CA II triplet in S-type Mira variable stars
The Ca II infrared triplet has been observed in 22 S-type Mira stars ofdifferent periods at various phases of the light cycle. The observationswere obtained with a spectrograph equipped with a single-stage imageintensifier tube, electrostatically focused, using an S-20 extended-redphotocathode. The objects were observed in two distinct spectralregions, in the red (5800-7800 A) and near-infrared (6800-8700 A), witha reciprocal linear dispersion of 87 A/mm, and an actual resolution ofabout 5 A. The spectrograms were measured with a Grant machine in itsdensitometer mode and reduced on a computer. The Ca II infrared emissionlines appear around a phase of 0.80, i.e., close to the phase whenhydrogen emission is observed first, and much earlier than the Ca II Hand K emission lines. The differences in the radial velocity of the CaII infrared emission lines with respect to the absorption line spectrumare much smaller than those of the Ca II H and K lines. It is concludedthat the emission originates in a hot layer, created deep in theatmosphere by a shock front, which moves upwards as the phase advances.A shock velocity smaller than 45 km/s is compatible with theobservations and predicts the observed correlation of the strength ofthe Ca II emission lines with the period and spectral type at a maximum.
| A revised spectral classification system in the red for S stars
Low-dispersion observations of S stars in the region 5450-7000 A havebeen used to establish a revised temperature classification scheme forthese objects. Bands of TiO and ZrO and the Na D lines are found to beuseful in placing all S type stars on a common temperature scale.Temperature subtypes for those objects exhibiting both ZrO and TiO bandsare assigned by a modified version of the Keenan 1954 system. For thepure S stars, a new system is introduced utilizing the ZrO bands and theD lines. Comparisons between the revised types and photometric colorsdemonstrate an improvement over Kennan's system, especially for the pureS stars. Further, a new abundance index is proposed based on therelative strength of the bands of YO as compared to ZrO and TiO. Itappears that this index is fundamentally related to the C/O ratio,though it may also be affected somewhat by the general enhancement ofs-process elements.
| The brightest S-type stars in the infrared
Lists of the brightest stars of type S at infrared wavelengths, based onsearches in the IRC and AFCRL catalogs, are presented in the hope ofstimulating further spectroscopic observations of S stars in theinfrared; the importance of such observations is stressed. Anexamination of the K magnitudes of the brightest stars having variousdegrees of S characteristics shows that the marginal MS stars are morecommon than stars with strong S characteristics, although they are alsomore difficult to recognize. It is found that the number ratio of coolcarbon stars to S stars, when selected in the same way according toinfrared magnitude and region of the sky, is about 3:1.
| A general catalogue of S stars.
Not Available
| Classification of 831 two-micron sky survey sources south of +5 degrees.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80.1011H&db_key=AST
| The Distribution of the BD M-Type Stars Along the Galactic Equator.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958ApJ...128..510N&db_key=AST
| Classification of the S-Type Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954ApJ...120..484K&db_key=AST
| A Study of Low-Dispersion Spectra of M Stars in the Red Region.
Not Available
| Temperature classification of the S-type stars.
Not Available
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Pozíciós és asztrometriai adatok
| Csillagkép: | Vízöntő |
| Rektaszcenzió: | 19h03m09.89s |
| Deklináció: | +12°15'08.4" |
| Vizuális fényesség: | 8.39 |
| RA sajátmozgás: | 2.3 |
| Dec sajátmozgás: | -16 |
| B-T magnitude: | 10.821 |
| V-T magnitude: | 8.591 |
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