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A 10 μm spectroscopic survey of Herbig Ae star disks: Grain growth and crystallization
We present spectroscopic observations of a large sample of Herbig Aestars in the 10 μm spectral region. We perform compositional fits ofthe spectra based on properties of homogeneous as well as inhomogeneousspherical particles, and derive the mineralogy and typical grain sizesof the dust responsible for the 10 μm emission. Several trends arereported that can constrain theoretical models of dust processing inthese systems: i) none of the sources consists of fully pristine dustcomparable to that found in the interstellar medium; ii) all sourceswith a high fraction of crystalline silicates are dominated by largegrains; iii) the disks around more massive stars (M 2.5{M}ȯ, L 60 {L}ȯ) have a higherfraction of crystalline silicates than those around lower mass stars,iv) in the subset of lower mass stars (M 2.5 {M}ȯ)there is no correlation between stellar parameters and the derivedcrystallinity of the dust. The correlation between the shape andstrength of the 10 micron silicate feature reported by van Boekel et al.(2003) is reconfirmed with this larger sample. The evidence presented inthis paper is combined with that of other studies to present a likelyscenario of dust processing in Herbig Ae systems. We conclude that thepresent data favour a scenario in which the crystalline silicates areproduced in the innermost regions of the disk, close to the star, andtransported outward to the regions where they can be detected by meansof 10 micron spectroscopy. Additionally, we conclude that the finalcrystallinity of these disks is reached very soon after active accretionhas stopped.
| 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.
| 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.
| Improved Mean Positions and Proper Motions for the 995 FK4 Sup Stars not Included in the FK5 Extension
Not Available
| Asymptotic giant branch stars near the sun
Available red and near-infrared photometry and apparent motions of M, S,and C asymptotic giant branch (AGB) stars in the Bright Star Catalogueare tabulated and discussed. It is shown that the red and near infraredindices normally used for late-type stars are interchangeable except forcarbon stars. The M-type giants are variable with visual amplitudegreater than 0.05 mag. The reddening-free parameter m2 from Genevaphotometry is essentially a temperature parameter for M giants, whilethe reddening-free parameter d is a sensitive detector of blue stellarcompanions. The space density of AGB stars near the sun decreases by afactor of 35 in a temperature range 3800 to 3400 K. Two of the S starsnear the sun were found to have nearly equal space motions and may becomembers of the Arcturus group.
| Third list of corrections to the identifications of IRAS sources in Astron. & Astrophys Suppl. 65, 607 and Astron. J. 98, 931
Not Available
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| The Perkins catalog of revised MK types for the cooler stars
A catalog is presented listing the spectral types of the G, K, M, and Sstars that have been classified at the Perkins Observatory in therevised MK system. Extensive comparisons have been made to ensureconsistency between the MK spectral types of stars in the Northern andSouthern Hemispheres. Different classification spectrograms have beengradually improved in spite of some inherent limitations. In thecatalog, the full subclasses used are the following: G0, G5, G8, K0, K1,K2, K3, K4, K5, M0, M1, M2, M3, M4, M5, M6, M7, and M8. Theirregularities are the price paid for keeping the general scheme of theoriginal Henry Draper classification.
| IRAS catalogues and atlases - Atlas of low-resolution spectra
Plots of all 5425 spectra in the IRAS catalogue of low-resolutionspectra are presented. The catalogue contains the average spectra ofmost IRAS poiont sources with 12 micron flux densities above 10 Jy.
| Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL. III - 790 late-type bright stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...59...15A&db_key=AST
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הכנס מאמר חדש
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הכנס לינק חדש
משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | שדרית |
| התרוממות ימנית: | 11h17m19.00s |
| סירוב: | -67°49'25.0" |
| גודל גלוי: | 6.06 |
| מרחק: | 520.833 פארסק |
| תנועה נכונה: | 13.5 |
| תנועה נכונה: | -5.8 |
| B-T magnitude: | 8.361 |
| V-T magnitude: | 6.272 |
קטלוגים וכינוים:
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