Guilt by Association: The 13 Micron Dust Emission Feature and Its Correlation to Other Gas and Dust Features
A study of all full-scan spectra of optically thin oxygen-richcircumstellar dust shells in the database produced by the ShortWavelength Spectrometer on ISO reveals that the strength of severalinfrared spectral features correlates with the strength of the 13 μmdust feature. These correlated features include dust features at 19.8and 28.1 μm and the bands produced by warm carbon dioxide molecules(the strongest of which are at 13.9, 15.0, and 16.2 μm). The databasedoes not provide any evidence for a correlation of the 13 μm featurewith a dust feature at 32 μm, and it is more likely that a weakemission feature at 16.8 μm arises from carbon dioxide gas ratherthan dust. The correlated dust features at 13, 20, and 28 μm tend tobe stronger with respect to the total dust emission in semiregular andirregular variables associated with the asymptotic giant branch than inMira variables or supergiants. This family of dust features also tendsto be stronger in systems with lower infrared excesses and thus lowermass-loss rates. We hypothesize that the dust features arise fromcrystalline forms of alumina (13 μm) and silicates (20 and 28 μm).Based on observations with the ISO, a European Space Agency (ESA)project with instruments funded by ESA member states (especially thePrincipal Investigator countries: France, Germany, the Netherlands, andthe United Kingdom) and with the participation of the Institute of Spaceand Astronautical Science (ISAS) and the National Aeronautics and SpaceAdministration (NASA).
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Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
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The continuum spectrum of V1016 Ori
New photoelectric JHKLM observations were obtained for the star V1016Ori. Infrared variability of the system was detected. UBVRIJHKLMobservations are used to analyze the brightness of V1016 Ori outsideeclipse. Its flux is shown to consist of the following components: (1)the flux from a primary B0 V star, (2) the flux from a secondary A0 Vstar, (3) the flux from an infrared object (an infrared component), and(4) the flux from a dust envelope around the A0 secondary with thetemperature T_d = 1600 K and the equivalent radius R_d = 30 R_solar. Themagnitudes of the B0 and A0 stars corrected for interstellar reddeningare V_1 = (6.03 +/- 0.05) mag and V_2 = (8.4 +/- 0.2) mag, respectively.The effective temperature and bolometric luminosity of the infraredcomponent were estimated to be T ~ 3000 K and L_3 = 150 L_solar. Theinfrared component may be in the Hayashi stage.
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SiO masers in OH/IR stars, proto-planetary and planetary nebulae
We present a search for SiO masers towards a sample of 126 objectsincluding OH/IR stars, proto-planetary and planetary nebulae. Allobjects are classified as oxygen-rich, and most of them are associatedwith OH or H_2O masers. SiO masers were found only in variable objectslike the OH/IR stars and a few objects classified as proto-planetarynebulae, but with variable central stars that may be part of binarysystems. In one object, OH 15.7+0.8, which appears to be varyingirregularly and most likely recently left the AGB, an SiO maser wastentatively detected. Thus, we conclude that variability and SiO maseremission are closely linked, and that SiO masers disappear very soonafter a star has reached the end of the AGB, when pulsation and massloss cease. Tables 1 and 2 are available at the CDS via anonymous ftp130.79.128.5 or via http://cdsweb.u-strasbg.fr/Abstract.html and Fig. 1can be found in the on-line version of A\&AS viahttp://www.ed-phys.fr
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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.
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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.
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Professional-amateur collaboration in variable star research: V. Observations of yellow semi-regular variables
Not Available
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Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
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Characterization and proportion of very cold C-rich circumstellar envelopes
The paper develops a method for identification of very cold C-richcircumstellar envelopes (CSEs) in IR regions colder than region VII(i.e., larger value of IRAS flux ratio S25/S12), by reviewing thedifferent criteria and by identifying C-rich CSEs in a sample of 228bright IRAS sources. By using the results of OH surveys and catalogstogether with the results of additional HCN/CO millimeter observationsperformed on critical classes of objects, a C/O classification isproposed for 94 percent of the sources with a good probability. It isshown that the low-resolution spectra by themselves are a reasonable andeasy way to identify C-rich late AGB CSEs. For post-AGB object with coldCSEs, HCN and OH observations or visible/near IR spectroscopy arenecessary.
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New low-resolution spectrometer spectra for IRAS sources
Low-resolution spectra of 486 IRAS point sources with Fnu(12microns) in the range 20-40 Jy are presented. This is part of an effortto extract and classify spectra that were not included in the Atlas ofLow-Resolution Spectra and represents an extension of the earlier workby Volk and Cohen which covers sources with Fnu(12 microns)greater than 40 Jy. The spectra have been examined by eye and classifiedinto nine groups based on the spectral morphology. This newclassification scheme is compared with the mechanical classification ofthe Atlas, and the differences are noted. Oxygen-rich stars of theasymptotic giant branch make up 33 percent of the sample. Solid statefeatures dominate the spectra of most sources. It is found that thenature of the sources as implied by the present spectral classificationis consistent with the classifications based on broad-band colors of thesources.
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1612 MHz OH survey of IRAS point sources. I - Observations made at Dwingeloo, Effelsberg and Parkes
The data from a large sky survey are presented including a northernpilot study and a detailed southern study in which detections are biasedtoward the most evolved sources and distant sources. Both areinvestigated at the 1612-MHz transition of OH to take advantage of thestrongest line for AGB stars with optically thick dust shells. The IRASsources are chosen by considering their IR colors related to fluxes at12, 25, and 60 microns. Observations are reported for 2703 IRAS pointsources at the 1612-MHz transition, and 738 OH/IR stars are detected.The survey identifies 597 of the sources as previously unidentified, and95 percent of the OH profiles observed have twin-peak masercharacteristics which are related to emission from expandingcircumstellar shells. The other 5 percent of the sources are concludedto be transition objects between OH/IR stars and planetary nebulae.
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Colour excesses and absolute magnitudes for non-Cepheid F-G supergiants from uvbybeta photometry
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990A&A...239..205A&db_key=AST
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The circumstellar silicate dust as seen by IRAS. I - Opacity and temperature
The study deals with objects included in the IRAS low-resolution spectra(LRS) catalog and exhibiting the 10-micron feature. A radiative transfermodel is outlined, and the parameters involved are defined along withthe initial choice of the proposed investigating procedure. Thenumerical models computed with the final choice of the best values ofopacities and grain condensation radii are presented. A principle of thetailoring procedure leading to the final choice is covered with emphasisplaced on the 10-micron feature intensity as a function of the (25/12)color and red supergiants. It is noted that the models agree withtwo-color diagrams and with the observed spectral shapes, and that thedust properties are uniform except for the sparsely populated LRS class6n.
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Mass-losing M supergiants in the solar neighborhood
A list of the 21 mass-losing red supergiants (20 M type, one G type; Lgreater than 100,000 solar luminosities) within 2.5 kpc of the sun iscompiled. These supergiants are highly evolved descendants ofmain-sequence stars with initial masses larger than 20 solar masses. Thesurface density is between about 1 and 2/sq kpc. As found previously,these stars are much less concentrated toward the Galactic center thanW-R stars, which are also highly evolved massive stars. Although withconsiderable uncertainty, it is estimated that the mass return by the Msupergiants is somewhere between 0.00001 and 0.00003 solar mass/sq kpcyr. In the hemisphere facing the Galactic center there is much less massloss from M supergiants than from W-R stars, but, in the anticenterdirection, the M supergiants return more mass than do the W-R stars. Theduration of the M supergiant phase appears to be between 200,000 and400,000 yr. During this phase, a star of initially at least 20 solarmasses returns perhaps 3-10 solar masses into the interstellar medium.
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The probable dust formation episode around Rho Cassiopeiae
By comparing IRAS photometry with previous 10-micron data, it appearsthat dust formed in the circumstellar envelope around the supergiant Gstar, Rho Cas, sometime between 1973 and 1983. This dust formation mayhave been the consequence of the gas outflowing and cooling from theintense mass outburst of 1946. In 1983, the dust was detected at atemperature between 600 and 800 K at a distance between 10 to the 15thcm and 4 x 10 to the 15th cm from the star. While the dust-to-gas ratioin the circumstellar envelope may be as low as 0.00001 and thus muchlower than in other mass-losing stars, the luminosity of Rho Cas issufficiently large that radiation pressure on this dust might bedynamically important in helping to drive mass loss.
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Supergiants and the Galactic metallicity gradient. II - Spectroscopic abundances for 64 distant F- to M-type supergiants
The metallicity gradient in the Galactic disk from in situ stars withvisual magnitude ranging from 6 to 10 is analyzed. Atmosphericparameters and detailed chemical abundances for 64 Population Isupergiants of spectral types F through M and luminosity classes Iathrough II have been determined. The derived Fe/H ratios ranging from-0.5 to + 0.7 show a mean value of +0.13 with an estimated uncertaintyof + or - 0.2. A subset of 25 supergiants fainter than 7th magnitudelying in the direction of the Galactic center shows a Fe/H mean of +0.18+ or - 0.04, while a similar sample of 15 faint supergiants lying in thedirection of the Galactic anticenter shows a lower Fe/H mean of +0.07 +or - 0.06. For a sample of bright supergiants analyzed by Luck andLambert (1985), the mean abundance pattern for all 64 stars showed thefollowing: deficient C and O along with enhancement of N, indicatingmixing of CNO-cycled material to the stellar surfaces; an apparent Srenhancement attributed to departures from LTE; and an essentially solarpattern of other chemical elements.
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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.
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Infrared circumstellar shells - Origins, and clues to the evolution of massive stars
The infrared fluxes, spatial and spectral characteristics for a sampleof 111 supergiant stars of spectral types F0 through M5 are tabulated,and correlations examined with respect to the nature of theircircumstellar envelopes. One-fourth of these objects were spatialyresolved by IRAS at 60 microns and possess extended circumstellar shellmaterial, with implied expansion ages of about 10 to the 5th yr.Inferences about the production of dust, mass loss, and the relation ofthese characteristics of the evolution of massive stars, are discussed.
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Lunar occultations of IRAS point sources, 1991-2000
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989ApJS...69..651C&db_key=AST
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Mass loss from stars : the universal formula for mass loss rate
Not Available
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A unified formula for mass-loss rate of O to M stars
A formula for stellar mass-loss rate has been derived using conservationequations of mass and momentum for coronal and continuumradiation-driven wind. The derived mass-loss rate formula has been foundto be consistent with the observed mass-loss rates for stars from O to Mspectral type. Two constant parameters appearing in the mass-loss rateformula have been found to have values for special group of stars suchas Be-stars, which are different from the majority of stars.
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Mass loss rates in the Hertzsprung-Russell diagram
Mass loss rates have been collected for 271 stars of spectral type Othrough M, primarily of population I. Good agreement is found forresults obtained according to six different methods, and it is shownthat the mass loss rate data can be well represented by one empiricalinterpolation formula as a function of the effective temperature andluminosity. The chemically evolved stars are shown to have mass lossrates which are larger than those of normal stars occupying the samepositions in the Hertzprung-Russell diagram by factors of 160 forWolf-Rayet stars and 11 for C-type stars.
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Far-infrared circumstellar 'debris' shell of red supergiant stars
An examination of IRAS data of red supergiant stars in the field and ingalactic OB star associations indicates the presence of substantialamounts of 60-micron emitting material extending several arcminutesaround many such sources. The characteristics of these large shells arediscussed in terms of remnants of ongoing mass loss, and a simple modeldeveloped for the case of Alpha Orionis, in particular.
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IRAS observations of the cool galactic hypergiants
Not Available
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The MK classification and its calibration
The system of spectral classification is described as it has developedfrom the original Yerkes Atlas (Morgan, Keenan, Kelman 1943) untiltoday. The word 'developed' is used because any system that is to remainuseful must be flexible enough to adapt not only to improved techniquesof measurement but also to new theoretical insights into the variablesthat actually determine the energy spectrum of a star in all itsfascinating but sometimes frustrating detail. The discussion does notconsider the criteria of classification but is confined to the resultingset of temperature types and luminosity classes. Chemical composition isexamined as a third variable. Tabulated and plotted informationincludes: MK temperature subclasses; lists of MK types of fainter stars;published calibrations of luminosity classes for early-type stars;calibration of MK luminosity classes for types later than F8; thedistribution among groups of the 426 stars in the author's current listof best types; and the effects of metal deficiencies on spectra of KOIII stars. The revised MK classification can be applied to all but a fewpercent of the stars later in type than GO. For the two-thirds of thesethat have approximately solar composition no abundance index is needed;for most of the remainder one abundance index suffices.
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Nineteen new spectroscopic binaries and the rate of binary stars among F-M supergiants
Nineteen spectroscopic binaries (SBs) have been discovered in radialvelocity measurements made with the CORAVEL spectrophotometer on 181northern F-M supergiants. The rate of detected SBs among northern F-Msupergiants is 21 percent, without any dependence on spectral orluminosity class. The study of the binary F-M supergiants with knownorbital elements indicates that all the systems with a period smallerthan the critical value P(circ) have a nearly circular orbit. The valueof P(circ) depends on the luminosity class, being 400-600 d for class Iband 2000-7000 d for class Ia. This circularization of the orbits may bedue to the transfer of angular momentum during the phase of binary massexchange.
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Revised MK Spectral Standard Stars Later than G0
Not Available
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The circumstellar envelopes of F- and G-type supergiants in the Large Magellanic Cloud
The outer atmospheres of four F- and G-type supergiants in the LMC arecompared with those of their Milky Way counterparts by means of 2.5 and5.1 A/mm high dispersion Echelle spectra. Na I D line doubling indicatesextensive circumstellar envelopes, mass loss rates greater than 0.00001solar masses/year, and outflow velocities of 10-60 km/sec. The Ca II Hand K lines yield new data on extragalactic star chromospheres.
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High-dispersion spectroscopy of the most luminous F- and G-type supergiants in the Large Magellanic Cloud and the Milky Way
High-resolution spectroscopic observations of the most luminous F- andG-type supergiant stars in the Large Magellanic Cloud and in the Galaxyare compared. High-dispersion echelle spectrograms, at dispersions of2.5 and 5.1 A/mm, were obtained together with optical and infraredphotometry for the four brightest LMC supergiants and seven Galacticsupergiants of comparable spectral types and luminosities. The LMCsupergiants are all observed to exhibit line doubling in the Na I Dlines, while no evidence for circumstellar line cores or line doublingis seen in either Ca I 4226 A or Sr II 4077 A. The galactic yellowsupergiants also show evidence for broad diffuse or doubled lines. TheCa II H and K core emission profiles along with the doubled linesindicate extensive circumstellar envelopes, and lead to estimates ofmass-loss rates in excess of 0.0001 solar mass/year. It is suggestedthat this mass loss rate may be explained by an outer atmosphericstructure consisting of an inner shell in which material circulatesbetween an extended atmosphere and the photosphere, and an outer shellfrom which matter outflow takes place.
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Some aspects of the spectroscopic behavior of the stars of highest luminosity in the region of the Hertzsprung gap
Abstract image available at:http://adsabs.harvard.edu/abs/1981ApJ...243..894M
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