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The Ages of Elliptical Galaxies from Infrared Spectral Energy Distributions
The mean ages of early-type galaxies obtained from the analysis ofoptical spectra give a mean age of 8 Gyr at z=0, with 40% being youngerthan 6 Gyr. Independent age determinations are possible by usinginfrared spectra (5-21 μm), which we have obtained with the InfraredSpectrograph on Spitzer. This age indicator is based on the collectivemass-loss rate of stars, in which mass loss from AGB stars produces asilicate emission feature at 9-12 μm. This feature decreases morerapidly than the shorter wavelength continuum as a stellar populationages, providing an age indicator. From observations of 30 nearbyearly-type galaxies, 29 show a spectral energy distribution dominated bystars, and one has significant emission from the ISM and is excluded.The infrared age indicators for the 29 galaxies show them all to be old,with a mean age of about 10 Gyr and a standard deviation of only a fewGyr. This is consistent with the ages inferred from the values ofM/LB, but is inconsistent with the ages derived from theoptical line indices, which can be much younger. All of these ageindicators are luminosity weighted and should be correlated, even ifmultiple-age components are considered. The inconsistency indicates thatthere is a significant problem with either the infrared and theM/LB ages, which agree, or with the ages inferred from theoptical absorption lines.
| Mid-Infrared Spectroscopy of Carbon Stars in the Small Magellanic Cloud
We have observed a sample of 36 objects in the Small Magellanic Cloud(SMC) with the Infrared Spectrometer on the Spitzer Space Telescope.Nineteen of these sources are carbon stars. An examination of the near-and mid-infrared photometry shows that the carbon-rich and oxygen-richdust sources follow two easily separated sequences. A comparison of thespectra of the 19 carbon stars in the SMC to spectra from the InfraredSpace Observatory (ISO) of carbon stars in the Galaxy revealssignificant differences. The absorption bands at 7.5 and 13.7 μm dueto C2H2 are stronger in the SMC sample, and theSiC dust emission feature at 11.3 μm is weaker. Our measurements ofthe MgS dust emission feature at 26-30 μm are less conclusive, butthis feature appears to be weaker in the SMC sample as well. All ofthese results are consistent with the lower metallicity in the SMC. Thelower abundance of SiC grains in the SMC may result in less efficientcarbon-rich dust production, which could explain the excessC2H2 gas seen in the spectra. The sources in theSMC with the strongest SiC dust emission tend to have redder infraredcolors than the other sources in the sample, which implies moreamorphous carbon, and they also tend to show stronger MgS dust emission.The weakest SiC emission features tend to be shifted to the blue; thesespectra may arise from low-density shells with large SiC grains.
| The Detection of Crystalline Silicates in Ultraluminous Infrared Galaxies
Silicates are an important component of interstellar dust, and thestructure of these grains (amorphous or crystalline) is sensitive to thelocal physical conditions. We have studied the infrared spectra of asample of ultraluminous infrared galaxies (ULIRGs). Here we report thediscovery of weak, narrow absorption features at 11, 16, 19, 23, and 28μm, characteristic of crystalline silicates, superimposed on thebroad absorption bands at 10 and 18 μm due to amorphous silicates ina subset of this sample. These features betray the presence offorsterite (Mg2SiO4), the magnesium-rich endmember of the olivines. Previously, crystalline silicates have only beenobserved in circumstellar environments. The derived fraction offorsterite to amorphous silicates is typically 0.1 in these ULIRGs. Thisis much larger than the upper limit for this ratio in the interstellarmedium of the Milky Way, 0.01. These results suggest that the timescalefor injection of crystalline silicates into the ISM is short in amerger-driven starburst environment (e.g., as compared to the total timeto dissipate the gas), pointing toward massive stars as a prominentsource of crystalline silicates. Furthermore, amorphization due tocosmic rays, which is thought to be of prime importance for the localISM, lags in vigorous starburst environments.
| The Unusual Silicate Dust around HV 2310, an Evolved Star in the Large Magellanic Cloud
The spectrum of HV 2310, an evolved star in the Large Magellanic Cloud,taken with the Infrared Spectrograph (IRS) on the Spitzer SpaceTelescope, reveals the presence of an optically thin shell of silicatedust with unusual spectral structure in the 10 μm feature: anemission peak at 9.7 μm, a saddle at 10.4 μm, and an extendedshoulder to 11.2 μm. This structure is similar to spectra fromcrystalline silicate grains, and of the available optical constants,forsterite provides the best fit. The spectrum also shows structure at14 μm that may arise from an unidentified dust feature.
| Mid-Infrared Spectra of Polycyclic Aromatic Hydrocarbon Emission in Herbig Ae/Be stars
We present spectra of four Herbig Ae/Be stars obtained with the InfraredSpectrograph (IRS) on the Spitzer Space Telescope. All four of thesources show strong emission from polycyclic aromatic hydrocarbons(PAHs), with the 6.2 μm emission feature shifted to 6.3 μm and thestrongest CC skeletal-mode feature occurring at 7.9 μm instead of at7.7 μm, as is often seen. Remarkably, none of the four stars hassilicate emission. The strength of the 7.9 μm feature varies withrespect to the 11.3 μm feature among the sources, indicating that wehave observed PAHs with a range of ionization fractions. The ionizationfraction is higher for systems with hotter and brighter central stars.Two sources, HD 34282 and HD 169142, show emission features fromaliphatic hydrocarbons at 6.85 and 7.25 μm. The spectrum of HD 141569shows a previously undetected emission feature at 12.4 μm that may berelated to the 12.7 μm PAH feature. The spectrum of HD 135344, thecoolest star in our sample, shows an unusual profile in the 7-9 μmregion, with the peak emission to the red of 8.0 μm and no 8.6 μmPAH feature.
| R CrB Candidates in the Small Magellanic Cloud: Observations of Cold, Featureless Dust with the Spitzer Infrared Spectrograph
We observed 36 evolved stars in the Small Magellanic Cloud (SMC) usingthe low-resolution mode of the Infrared Spectrograph (IRS) on theSpitzer Space Telescope. Two of these stars, MSX SMC 014 and 155, havenearly featureless spectral energy distributions over the IRS wavelengthrange (5.2-35 μm) and Fν peaking at ~8-9 μm. Thedata can be fit by sets of amorphous carbon shells or by single 600-700K blackbodies. The most similar spectra found in extant spectraldatabases are of R CrB, although the spectral structure seen in R CrBand similar stars is much weaker or absent in the SMC sources. Both SMCstars show variability in the near-infrared. Ground-based visual spectraconfirm that MSX SMC 155 is carbon-rich, as expected for R CrB (RCB)stars, and coincides with an object previously identified as an RCBcandidate. The temperature of the underlying star is lower for MSX SMC155 than for typical RCB stars. The strength of the C2 Swanbands and the low temperature suggest that it may be a rare DY Per-typestar, only the fifth such identified. MSX SMC 014 represents a new RCBcandidate in the SMC, bringing the number of RCB candidates in the SMCto six. It is the first RCB candidate discovered with Spitzer and thefirst identified by its infrared spectral characteristics rather thanits visual variability.
| The Detection of Silicate Emission from Quasars at 10 and 18 Microns
We report the spectroscopic detection of silicate emission at 10 and 18μm in five PG quasars, the first detection of these two features ingalaxies outside the Local Group. This finding is consistent with theunification model for active galactic nuclei (AGNs), which predicts thatan AGN torus seen pole-on should show a silicate emission feature in themid-infrared. The strengths of the detected silicate emission featuresrange from 0.12 to 1.25 times the continuum at 10 μm and from 0.20 to0.79 times the continuum at 18 μm. The silicate grain temperaturesinferred from the ratio of 18 μm to 10 μm silicate features underthe assumption of optically thin emission range from 140 to 220 K.
| Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
The availability of the Hipparcos Catalogue has triggered many kinematicand dynamical studies of the solar neighbourhood. Nevertheless, thosestudies generally lacked the third component of the space velocities,i.e., the radial velocities. This work presents the kinematic analysisof 5952 K and 739 M giants in the solar neighbourhood which includes forthe first time radial velocity data from a large survey performed withthe CORAVEL spectrovelocimeter. It also uses proper motions from theTycho-2 catalogue, which are expected to be more accurate than theHipparcos ones. An important by-product of this study is the observedfraction of only 5.7% of spectroscopic binaries among M giants ascompared to 13.7% for K giants. After excluding the binaries for whichno center-of-mass velocity could be estimated, 5311 K and 719 M giantsremain in the final sample. The UV-plane constructed from these datafor the stars with precise parallaxes (σπ/π≤20%) reveals a rich small-scale structure, with several clumpscorresponding to the Hercules stream, the Sirius moving group, and theHyades and Pleiades superclusters. A maximum-likelihood method, based ona Bayesian approach, has been applied to the data, in order to make fulluse of all the available stars (not only those with precise parallaxes)and to derive the kinematic properties of these subgroups. Isochrones inthe Hertzsprung-Russell diagram reveal a very wide range of ages forstars belonging to these groups. These groups are most probably relatedto the dynamical perturbation by transient spiral waves (as recentlymodelled by De Simone et al. \cite{Simone2004}) rather than to clusterremnants. A possible explanation for the presence of younggroup/clusters in the same area of the UV-plane is that they have beenput there by the spiral wave associated with their formation, while thekinematics of the older stars of our sample has also been disturbed bythe same wave. The emerging picture is thus one of dynamical streamspervading the solar neighbourhood and travelling in the Galaxy withsimilar space velocities. The term dynamical stream is more appropriatethan the traditional term supercluster since it involves stars ofdifferent ages, not born at the same place nor at the same time. Theposition of those streams in the UV-plane is responsible for the vertexdeviation of 16.2o ± 5.6o for the wholesample. Our study suggests that the vertex deviation for youngerpopulations could have the same dynamical origin. The underlyingvelocity ellipsoid, extracted by the maximum-likelihood method afterremoval of the streams, is not centered on the value commonly acceptedfor the radial antisolar motion: it is centered on < U > =-2.78±1.07 km s-1. However, the full data set(including the various streams) does yield the usual value for theradial solar motion, when properly accounting for the biases inherent tothis kind of analysis (namely, < U > = -10.25±0.15 kms-1). This discrepancy clearly raises the essential questionof how to derive the solar motion in the presence of dynamicalperturbations altering the kinematics of the solar neighbourhood: doesthere exist in the solar neighbourhood a subset of stars having no netradial motion which can be used as a reference against which to measurethe solar motion?Based on observations performed at the Swiss 1m-telescope at OHP,France, and on data from the ESA Hipparcos astrometry satellite.Full Table \ref{taba1} is only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/430/165}
| Fire and Ice: Spitzer Infrared Spectrograph (IRS) Mid-Infrared Spectroscopy of IRAS F00183-7111
We report the detection of strong absorption and weak emission featuresin the 4-27 μm Spitzer Infrared Spectrograph (IRS) spectrum of thedistant ultraluminous infrared galaxy IRAS F00183-7111 (z=0.327). Theabsorption features of CO2 and CO gas, water ice,hydrocarbons, and silicates are indicative of a strongly obscured(A9.6>=5.4 AV>=90) and complex line of sightthrough both the hot diffuse interstellar medium and shielded coldmolecular clouds toward the nuclear power source. From the profile ofthe 4.67 μm CO fundamental vibration mode, we deduce that theabsorbing gas is dense (n~106 cm-3) and warm (720K) and has a CO column density of ~1019.5 cm-2,equivalent to NH~1023.5 cm-2. The hightemperature and density, as well as the small inferred size (<0.03pc), locates this absorbing gas close to the power source of thisregion. Weak emission features of molecular hydrogen, polycyclicaromatic hydrocarbons (PAHs), and Ne+, likely associated withstar formation, are detected against the 9.7 μm silicate feature,indicating an origin away from the absorbing region. Based on the 11.2μm PAH flux, we estimate the star formation component to beresponsible for up to 30% of the IR luminosity of the system. While ourmid-infrared spectrum shows no telltale signs of active galactic nucleus(AGN) activity, the similarities to the mid-infrared spectra of deeplyobscured sources (e.g., NGC 4418) and AGN hot dust (e.g., NGC 1068), aswell as evidence from other wavelength regions, suggest that the powersource hiding behind the optically thick dust screen may well be aburied AGN.
| The Serendipitous Discovery of a Debris Disk around the A Dwarf HD 46190
The Infrared Spectrograph on the Spitzer Space Telescope has observedseveral A dwarfs as potential standards and cross-calibrators, and oneof these stars, HD 46190, shows the spectroscopic signature of a debrisdisk. The disk produces a spectral excess that can be fitted with a coolblackbody of ~81 K. If the emitting particles are spherical blackbodies,they would lie at a distance of ~82 AU from the central star. Thespectrum from the disk can also be fitted with a spectrum risingproportionally with wavelength, and this spectral behavior is consistentwith material falling into the inner disk as a result ofPoynting-Robertson drag.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable 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/qcar?J/A+A/367/521
| A catalog of rotational and radial velocities for evolved stars
Rotational and radial velocities have been measured for about 2000evolved stars of luminosity classes IV, III, II and Ib covering thespectral region F, G and K. The survey was carried out with the CORAVELspectrometer. The precision for the radial velocities is better than0.30 km s-1, whereas for the rotational velocity measurementsthe uncertainties are typically 1.0 km s-1 for subgiants andgiants and 2.0 km s-1 for class II giants and Ib supergiants.These data will add constraints to studies of the rotational behaviourof evolved stars as well as solid informations concerning the presenceof external rotational brakes, tidal interactions in evolved binarysystems and on the link between rotation, chemical abundance and stellaractivity. In this paper we present the rotational velocity v sin i andthe mean radial velocity for the stars of luminosity classes IV, III andII. Based on observations collected at the Haute--Provence Observatory,Saint--Michel, France and at the European Southern Observatory, LaSilla, Chile. Table \ref{tab5} also available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Evolution of X-ray activity and rotation on G-K giants
The recent availability of stellar parallaxes provided by the Hipparcosstar catalogue (ESA 1997) enables an accurate determination of thepositions of single field giants in a theoretical H-R diagram and areliable estimate of their masses. The present study combines these newastrometric data with previously published X-ray fluxes and rotationalvelocities. The results confirm the existence of a sharp decrease ofX-ray emission at spectral type K1 for 2.5 M_sun < M < 5 M_sungiants. The study shows that the rotational velocity of these starsreaches a minimum at the same location in the H-R diagram. However, notight relationship between X-ray luminosities and projected equatorialvelocities was found among the sample stars. I suggest that theseresults could reflect the importance of differential rotation indetermining the level of coronal emission among >= 2.5Msun G and K giants. The restoration of rigid rotation at thebottom of the red giant branch could prevent the maintenance of largescale magnetic fields, thus explaining the sharp decrease of coronalX-ray emission at spectral type K1.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Einstein Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars
Results are presented of an extensive X-ray survey of 380 giant andsupergiant stars of spectral types from F to M, carried out with theEinstein Observatory. It was found that the observed F giants orsubgiants (slightly evolved stars with a mass M less than about 2 solarmasses) are X-ray emitters at the same level of main-sequence stars ofsimilar spectral type. The G giants show a range of emissions more than3 orders of magnitude wide; some single G giants exist with X-rayluminosities comparable to RS CVn systems, while some nearby large Ggiants have upper limits on the X-ray emission below typical solarvalues. The K giants have an observed X-ray emission level significantlylower than F and F giants. None of the 29 M giants were detected, exceptfor one spectroscopic binary.
| The binary nature of the barium stars. II - Velocities, binary frequency, and preliminary orbits
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983ApJ...268..264M&db_key=AST
| Radial velocities of a random sample of K giant stars and implications concerning multiplicity among giant stars in clusters
Radial velocities, with precisions better than 0.40 km/sec have beenobtained for a random sample of 40 K giant stars. The frequency osspectroscopic binaries detected in this sample from observations over a3 year time span is 15% to 20%, and more are probably long-periodbinaries. A comparison is made between this sample and others includingthe sample of giants measured by Gunn and Griffin (1979) in the globularcluster M3. The comparison with M3 indicates that, when allowance ismade for the sizes and masses of the stars, there is no evidence frompublished velocity data that M3 is deficient in binaries.
| A magnitude limited stellar X-ray survey and the F star X-ray luminosity function
An X-ray survey has been conducted of stars brighter than visualmagnitude 8.5 that have serendipitously fallen into the fields of viewof the Imaging Proportional Counter of the Einstein Observatory. Thesurvey includes 227 separate 1 x 1 deg fields, containing 274 stars witha visual magnitude of no more than 8.5 and covering a wide range ofspectral types and luminosity classes. X-ray emission was detected from33 stars, and upper limits have been determined for the remainder of thesample. F type stars dominate the detected sample, and most of these areshown to be dwarfs. An X-ray luminosity function for dF stars has beendeduced, and reveals that the average 0.2-4.0 keV luminosity of thesestars is around 10 to the 29th erg/sec. Constraints have been placed onthe high luminosity tails and medians of the X-ray luminosity functionsfor other types of stars.
| The binary nature of the barium stars
Radial-velocity spectrometer observations are presented that indicatethat Ba II stars are binary systems. The secondary stars of thesesystems have low masses, consistent with their being degenerate objectswhich have lost mass onto their primaries in a previous stage ofevolution. It is suggested that the Population II equivalents, the CHstars, may also be binary systems. This may be related to the fact thatthey are found only in globular clusters of the lowest centralconcentration.
| Photoelectric Observations of Vw-Draconis in 1977
Not Available
| Final catalogue of 229 photometric standards in UBV system near the selected areas 1-115
Not Available
| The corrected magnitudes and colours of 278 stars near S.A. 1-139 in the UBV system
Not Available
| The Application of an Oscilloscopic Microphotometer to the Spectral Classification of Late-Type Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954ApJ...119..613H&db_key=AST
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| Csillagkép: | Sárkány |
| Rektaszcenzió: | 17h01m16.70s |
| Deklináció: | +60°38'57.0" |
| Vizuális fényesség: | 6.13 |
| Távolság: | 108.225 parszek |
| RA sajátmozgás: | -43 |
| Dec sajátmozgás: | 39 |
| B-T magnitude: | 7.44 |
| V-T magnitude: | 6.256 |
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