Contents
Images
Upload your image
DSS Images Other Images
Related articles
Near-infrared spectroscopy of AGB star candidates in Fornax, Sculptor, and NGC 6822
Context: The asymptotic giant branch (AGB) phase is characterised bysubstantial mass loss that is accompanied by the formation of dust. Inextreme cases this will make the star no longer visible in the optical.For a better understanding of AGB evolution it is important to identifyand characterise these very red AGB stars. Aims: The first aim ofthis article is to improve the census of red AGB stars in three LocalGroup galaxies, based on near-IR spectroscopic observations of newcandidates with red 2MASS (J-K) colours. The opportunity is taken tocompare the near-IR spectra with those of Milky Way stars. Methods: We used ISAAC on the ESO VLT to take J and H-band spectra of36 targets in Fornax, Sculptor and NGC 6822. Results: Twelve newC-stars are found in Fornax, and one is confirmed in Sculptor. AllC-stars have (J-K) > 1.6, and are brighter than -3.55 in bolometricmagnitude. Ten new oxygen-rich late-type giant stars are identified inFornax, but none is extremely red or very luminous. Five luminous O-richAGB stars are identified in NGC 6822, of which 3 show water absorption,indicative of spectral type M. Again, none is as red as Milky Way OH/IRstars, but in this galaxy the list of candidate AGB stars is biasedagainst very red objects. In some C-stars with (J-K)>2 an extremelystrong 1.53 μm absorption band is found. These stars are probably allMira variables and the feature is related to the low temperature, highdensity chemistry that is a first step towards dust formation and massloss.Based on observations collected at the European Southern Observatory,Paranal, Chile (ESO programme 75.D-0152).Figure 6 is only available in electronic form via http://www.aanda.org
| The low-mass YSO CB230-A: investigating the protostar and its jet with NIR spectroscopy and Spitzer observations
Context: To investigate the earliest phases of star formation and studyhow newly-born stars interact with the surrounding medium, we performeda line and continuum survey at NIR and mm-wavelengths of a sample ofrelatively isolated Bok globules. Aims: We present a follow-upobservational program of a star-forming site in the globuleCB230. From narrow-band continuum observations ofthis site, we had discovered a bright [FeII] jet, which originates inthe low-mass YSO CB230-A. We aim to investigate thephysical properties of the region from where the jet is launched. Methods: Our analysis was carried out using low-resolution NIR spectraacquired with the camera NICS at the TNG telescope, with JH and HKgrisms and a 1 arcsec-wide slit. These observational data werecomplemented with infrared photometric data from the Spitzer spacetelescope archive. Results: The relevant physical properties ofCB230-A were constrained by SED fitting of fluxesfrom the NIR to the mm. The YSO spectrum exhibits a significant numberof atomic and molecular emission lines and absorption features. Thecharacteristics of this spectrum suggest that we are observing a regionin the close vicinity of CB230-A, i.e. itsphotosphere and/or an active accretion disk. The spectra of the knots inthe jet contain a large number of emission lines, including a rich setof [FeII] lines. Emission due to H2 and [FeII] are not spatiallycorrelated, confirming that [FeII] and H2 are excited by differentmechanisms, in agreement with the models where [FeII] tracesdissociative J-shocks and molecular hydrogen traces slower C-shocks. Byusing intensity ratios involving density-sensitive [FeII] lines, weestimated the electron densities along the jet to be 6 × 10^3-1× 104 cm-3. This indicates either highdensity post-shock regions of ionised gas or regions with a high degreeof ionisation. Conclusions: By combining the present data withpreviously obtained maps at NIR- and mm-wavelengths, the emergingscenario is that CB230-A is a Class 0/I YSO drivingan atomic jet that is observed to be almost monopolar probably due toits inclination to the plane of the sky and the resulting higherextinction of its red side. This primary jet appears to be sufficientlyenergetic to open the cavity visible in the NIR images and drive thelarge-scale molecular outflow observed at mm-wavelengths.CB230-A was revealed to be a good location to testthe innermost structure of accreting low-mass protostars.Appendices A and B are only available in electronic form athttp://www.aanda.org
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Near-IR spectroscopy of OH/IR stars in the Galactic centre
Context.Based on the expansion velocities of their circumstellar shells,Galactic centre (GC) OH/IR stars can be divided into two groups that arekinematically different and therefore believed to have evolved fromdifferent stellar populations.Aims.We studied the metallicitydistribution of the OH/IR stars population in the GC on the basis of atheoretical relation between EW(Na), EW(Ca), and EW(CO) and themetallicity.Methods.For 70 OH/IR stars in the GC, we obtainednear-IR spectra. The equivalent line-widths of Na I, Ca I,12CO(2, 0), and the curvature of the spectrum around 1.6μm due to water absorption were determined.Results.The near-IRspectrum of OH/IR stars is influenced by several physical processes.OH/IR stars are variable stars suffering high mass-loss rates. The dustthat is formed around the stars strongly influences the near-IR spectraand reduces the equivalent line-widths of Na I and Ca I. A similareffect is caused by the water content in the outer atmosphere of theOH/IR star. Because of these effects, it is not possible to determinethe metallicities of these stars with our low-resolution near-infraredspectroscopy.
| Reprocessing the Hipparcos data of evolved stars. III. Revised Hipparcos period-luminosity relationship for galactic long-period variable stars
We analyze the K band luminosities of a sample of galactic long-periodvariables using parallaxes measured by the Hipparcos mission. Theparallaxes are in most cases re-computed from the Hipparcos IntermediateAstrometric Data using improved astrometric fits and chromaticitycorrections. The K band magnitudes are taken from the literature andfrom measurements by COBE, and are corrected for interstellar andcircumstellar extinction. The sample contains stars of several spectraltypes: M, S and C, and of several variability classes: Mira, semiregularSRa, and SRb. We find that the distribution of stars in theperiod-luminosity plane is independent of circumstellar chemistry, butthat the different variability types have different P-L distributions.Both the Mira variables and the SRb variables have reasonablywell-defined period-luminosity relationships, but with very differentslopes. The SRa variables are distributed between the two classes,suggesting that they are a mixture of Miras and SRb, rather than aseparate class of stars. New period-luminosity relationships are derivedbased on our revised Hipparcos parallaxes. The Miras show a similarperiod-luminosity relationship to that found for Large Magellanic CloudMiras by Feast et al. (\cite{Feast-1989:a}). The maximum absolute Kmagnitude of the sample is about -8.2 for both Miras and semi-regularstars, only slightly fainter than the expected AGB limit. We show thatthe stars with the longest periods (P>400 d) have high mass lossrates and are almost all Mira variables.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA \cite{Hipparcos}).Table \ref{Tab:data1} 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/403/993
| 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 modelling of intermediate-age stellar populations. II. Average spectra for upper AGB stars, and their use
The upper Asymptotic Giant Branch (AGB) is populated with oxygen richand carbon rich Long Period Variables (LPVs). These stars are essentialcontributors to the near-IR light of intermediate age stellarpopulations. Individual observed spectra of LPVs are so diverse thatthey cannot be used directly in the synthesis of galaxy spectra. In thispaper, the library of individual spectra of Lançon & Wood(\cite{LM00_fluct}) is used to construct averages that can beincorporated conveniently in population synthesis work. The connectionbetween such spectra and stellar evolution tracks is discussed. In orderto select a sorting criterion and to define averaging bins for the LPVspectra, correlations between their spectrophotometric properties arereexamined. While optical properties and broad baseline colours such as(I-K) are well correlated, a large dispersion is observed when theseindices are plotted against near-IR ones. This is partly due to theintrinsic width of the upper AGB, which is illustrated by locating eachof the multiple observations of individual LPVs on the HR diagram. It isargued that broad baseline colour-temperatures are the most sensiblesorting criteria. The properties of the resulting sequence of averagespectra indeed vary regularly. We further address: (i) the bolometriccorrections and temperature scales needed to associate a spectrum with agiven point on a theoretical stellar evolution track (or isochrone),(ii) the simplifying assumptions that will be implicitely made whenusing the average spectra, (iii) potential biases in the sample ofLançon & Wood and their effects, (iv) the small contributionof LPVs to the interstellar hydrogen emission lines in galaxies. It isemphasized that an a posteriori calibration of the effective temperaturescale remains necessary, until consistent models for the evolution, thepulsation and the spectral appearance of LPVs become available. Wesuggest a recipe for the use of the average spectra at variousmetallicities.
| Polarimetry of 167 Cool Variable Stars: Data
Multicolor photoelectric polarimetry is presented for 167 stars, most ofwhich are variable stars. The observations constitute a data set thatfor some stars covers a time span of 35 yr. Complex variations are foundover time and wavelength and in both the amount of polarization and itsposition angle, providing constraints for understanding the polarizingenvironments in and around these cool stars.
| Long period variable stars: galactic populations and infrared luminosity calibrations
In this paper HIPPARCOS astrometric and kinematic data are used tocalibrate both infrared luminosities and kinematical parameters of LongPeriod Variable stars (LPVs). Individual absolute K and IRAS 12 and 25luminosities of 800 LPVs are determined and made available in electronicform. The estimated mean kinematics is analyzed in terms of galacticpopulations. LPVs are found to belong to galactic populations rangingfrom the thin disk to the extended disk. An age range and a lower limitof the initial mass is given for stars of each population. A differenceof 1.3 mag in K for the upper limit of the Asymptotic Giant Branch isfound between the disk and old disk galactic populations, confirming itsdependence on the mass in the main sequence. LPVs with a thin envelopeare distinguished using the estimated mean IRAS luminosities. The levelof attraction (in the classification sense) of each group for the usualclassifying parameters of LPVs (variability and spectral types) isexamined. Table only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/374/968 or via ASTRIDdatabase (http://astrid.graal.univ-montp2.fr).
| 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.
| On the Variability of K5-M Stars
I investigate the Hipparcos Satellite photometry of K5-M stars to seethe pattern of activity of these stars. A few stars for which furtherstudy is desirable are identified.
| A library of 0.5 to 2.5 mu m spectra of luminous cool stars
We present a library of 0.5-2.5 mu m digital spectra of cool, mostlyvariable, giant and supergiant stars which should be useful for spectralsynthesis applications, as well as for comparison with theoretical modelatmosphere calculations. The library includes carbon stars, GalacticBulge and Magellanic Cloud stars, and OH/IR stars. The stars observedcover a range of metallicities and masses. Most variable objects wereobserved several times, at different phases of their pulsation cycle. Wediscuss the effects of various fundamental parameters and of variabilityon the spectra. Based on period-luminosity relations and stellarevolutionary tracks, we tentatively assign initial masses to eachobject.
| Mira kinematics from Hipparcos data: a Galactic bar to beyond the Solar circle
The space motions of Mira variables are derived from radial velocities,Hipparcos proper motions and a period-luminosity relation. Thepreviously known dependence of Mira kinematics on the period ofpulsation is confirmed and refined. In addition, it is found that Miraswith periods in the range 145-200d in the general Solar neighbourhoodhave a net radial outward motion from the Galactic Centre of75+/-18kms-1. This, together with a lag behind the circularvelocity of Galactic rotation of 98+/-19kms-1, is interpretedas evidence for an elongation of their orbits, with their major axesaligned at an angle of ~17° with the Sun-Galactic Centre line,towards positive Galactic longitudes. This concentration seems to be acontinuation to the Solar circle and beyond of the bar-like structure ofthe Galactic bulge, with the orbits of some local Miras probablypenetrating into the bulge. These conclusions are not sensitive to thedistance scale adopted. A further analysis is given of the short-period(SP) red group of Miras discussed in companion papers in this series. InAppendix A the mean radial velocities and other data for 842 oxygen-richMira-like variables are tabulated. These velocities were derived frompublished optical and radio observations.
| Optical and near-infrared spectrophotometric properties of Long Period Variables and other luminous red stars
Based on a new and large sample of optical and near-infrared spectraobtained at the Mount Stromlo and Siding Spring Observatories(Lançon & Wood 1998; Lançon & Wood, inpreparation), spectrophotometric properties of cool oxygen- andcarbon-rich Long Period Variables and supergiants are presented.Temperatures of oxygen-rich stars are assigned by comparison withsynthetic spectra computed from up-to-date oxygen-rich model atmospheregrids. The existence of reliable optical and near-infrared temperatureindicators is investigated. A narrow relation between the bolometriccorrection BC_I and the broad-band colour I-J is obtained foroxygen-rich cool stars. The ability of specific near-infrared indices toseparate luminosity classes, atmospheric chemistry or variabilitysubtypes is discussed. Some comments are also given on extinctioneffects, water band strengths in Long Period Variables and theevaluation of \element[][12]{CO}/\element[][13]{CO} ratio in red giants.
| Period-Luminosity-Colour distribution and classification of Galactic oxygen-rich LPVs. I. Luminosity calibrations
The absolute K magnitudes and kinematic parameters of about 350oxygen-rich Long-Period Variable stars are calibrated, by means of anup-to-date maximum-likelihood method, using Hipparcos parallaxes andproper motions together with radial velocities and, as additional data,periods and V-K colour indices. Four groups, differing by theirkinematics and mean magnitudes, are found. For each of them, we alsoobtain the distributions of magnitude, period and de-reddened colour ofthe base population, as well as de-biased period-luminosity-colourrelations and their two-dimensional projections. The SRa semiregulars donot seem to constitute a separate class of LPVs. The SRb appear tobelong to two populations of different ages. In a PL diagram, theyconstitute two evolutionary sequences towards the Mira stage. The Mirasof the disk appear to pulsate on a lower-order mode. The slopes of theirde-biased PL and PC relations are found to be very different from theones of the Oxygen Miras of the LMC. This suggests that a significantnumber of so-called Miras of the LMC are misclassified. This alsosuggests that the Miras of the LMC do not constitute a homogeneousgroup, but include a significant proportion of metal-deficient stars,suggesting a relatively smooth star formation history. As a consequence,one may not trivially transpose the LMC period-luminosity relation fromone galaxy to the other Based on data from the Hipparcos astrometrysatellite. Appendix B 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/Abstract.html
| 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.
| The Infrared Spectral Classification of Oxygen-rich Dust Shells
This paper presents infrared spectral classifications for a flux-limitedsample of 635 optically identified oxygen-rich variables includingsupergiants and sources on the asymptotic giant branch (AGB). Severalclasses of spectra from oxygen-rich dust exist, and these can bearranged in a smoothly varying sequence of spectral shapes known as thesilicate dust sequence. Classification based on this sequence revealsseveral dependencies of the dust emission on the properties of thecentral star. Nearly all S stars show broad emission features fromalumina dust, while most of the supergiants exhibit classic featuresfrom amorphous silicate dust. Mira variables with symmetric light curvesgenerally show broad alumina emission, while those with more asymmetriclight curves show classic silicate emission. These differences may arisefrom differences in the photospheric C/O ratio.
| 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.
| 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.
| Semiregular variables of types SRa and SRb. New JHKL'M-photometry for 200 stars.
This paper presents new JHKL'M observations of 200 Semiregular variables(SRVs) of types SRa and SRb. The sample was defined in Kerschbaum &Hron (1992a, Paper I) by means of a certain limit in bolometricalmagnitude. From the sample of 350 objects, 260 now have near infrared(NIR) photometry - for 60 of these stars data from the literature areused. In total 290 datasets are available because of some multipleobservations. We briefly compare the photometry obtained at differentobservatories. Small but significant differences are found. A firstanalysis of the photometry supports one of the main findings of Paper I.The, in many aspects inhomogeneous, O-rich semiregular variables oftypes SRa and SRb can be successfully split in two subgroups called the`blue' and `red'/`Mira' SRVs. A separation of the `red' SRVs fromintrinsic Miras additionally requires variability information.
| Circumstellar shells resolved in the IRAS survey data. I - Data processing procedure, results, and confidence tests
We have examined the IRAS 60 and 100 micron survey data covering 512evolved stars and young planetary nebulae for evidence of spatiallyresolved structure. A simple model, consisting of a central unresolvedsource surrounded by a resolved isothermal shell, was fitted to the datafor each star. Seventy-six stars were found to be resolved in the 60micron data. Tests have been performed to verify that the extendedstructure seen is not an artifact of the data-processing algorithm.
| Oxygen-rich semiregular and irregular variables
All the known oxygen-rich semiregulars and irregulars of spectralclasses K and M with the absolute value of B not greater than 30 deg,Delta(m) not less than 0.5 mag, and, for the semiregulars, periods inthe range of 50 to 400 d are compiled. On the basis of theirdistributions on the sky and their brightnesses in the K band at 2.2microns, it is argued that the semiregulars with a period of 300-400 dappear to belong to the same population as the 'thin disk' Miras in thesame period range and have an exponential scale height from the Galacticplane of about 250 pc. The semiregulars with a period range of 200 to300 d belong to the population of the 'thick disk' Miras with anexponential scale height from the Galactic plane of about 500 pc. On thebasis of the similarities of their space distributions and the presenceof Tc in their atmospheres, and using the pulsational mode calculationsby Ostlie and Cox (1986), it is suggested that the semiregulars with aperiod range of 100-150 d are first and second overtone pulsations ofthe same population of AGB stars as the Miras in their fundamentalpulsational mode with periods longer than 300 d.
| Near-infrared photometry of a sample of IRAS point sources
This paper presents the J, H, K, L, M photometry of 516 sourcespertaining to a sample of 787 sources which has been extracted from theIRAS Point Source Catalog in order to study the late stages of stellarevolution and the concomitant phenomena of mass loss. Three differentclssifications of these sources based on broad-band photometry and IRASlow-resolution spectra are given, and the distributions of the sourcesin terms of these classifications are presented. A subsample of peculiarsources, believed to have recently undergone a helium flash, has beenisolated using the K - L, (12-micron) color diagram. Some objectsmeriting further study are also mentioned.
| A survey of circumstellar CO emission from a sample of IRAS point sources
The first results from a survey of circumstellar CO(1-0) emission arepresented. The sources were selected from the IRAS point source catalogaccording to the IRAS color criteria described in van der Veen andHabing (1988). The sources have good quality fluxes at 12, 25, and 60microns, flux densities larger than 20 Jy at 25 microns, and aresituated more than 5 deg away from the Galactic plane. The survey isundertaken to study the relationship between mass loss rates, dustproperties, and the evolution along the AGB. The sample consists of 787sources and contains both oxygen and carbon-rich stars, including Miravariables, OH/IR objects, protoplanetary nebulae, planetary nebulae, and60-micron excess sources. So far, 519 objects, situated on both thenorthern and the southern sky, have been observed; 163 sources werefound to have circumstellar CO emission, and in 58 of these CO emissionhas not previously been detected.
| 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.
| A survey for infrared excesses among high galactic latitude SAO stars
This project involves extending the previous analysis of infraredexcesses among a volume-limited sample of 134 nearby A-K main-sequencestars to a magnitude-limited sample of stars, culled from the SAOCatalog, with excesses determined from the IRAS Point Source Catalogflux density ratios. This new sample includes 5706 B-M type stars, 379of which have infrared excesses. The objective involved use of astatistically complete survey of objects in a standard catalog in orderto assess the frequency with which different physical processes canaffect the infrared output of stars. These processes include, but arenot limited to, orbiting cold particle clouds and the onset of rapidmass loss. It is concluded that cold disks are consistent with theinfrared excesses found among A-G dwarfs and G-K giants in the sample.
| M Giant Populations and Galactic Structure
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990MNRAS.247..227F&db_key=AST
| Detection of 51 new 86 GHz SiO, V = 1, J = 2-1 masers associated with IRAS point sources
This paper reports the results of a search for southern stellar SiO, v =1, J = 2-1 masers in a survey of IRAS point sources. Out of the 116observed southern sources, 51 identified as new SiO, v = 1, J = 2-1masers, on the basis of their position in IRAS color-color plot. Ofthese, 42 masers have stellar identifications in IPSC, two arepreviously known non-IRAS IR objects, and six have no identification inIPSC.
| SiO masers in giant semi-regular variables and supergiants
A systematic study is presented of the SiO maser emission in nonregular(O-rich) variables: semiregular giants (SRGs) and supergiants (SGs),which was much less well known than for Miras (giant regular variables).It has been found that some SRGs and SGs attain the high level of maseremission characteristic of Miras, but others remain significantlyweaker. This has been found to hold for v = 1, 2 J = 1-0 and v = 1 J =2-1 masers. The well defined value of the SiO (peak flux)/IR(8-micronflux) ratio (about 1/5), attained by the Miras and by the strongest SRGsand SGs, is interpreted as representing the maximum efficiency of theradiative pumping. The low SiO/IR ratio of many SRGs and SGs is shown tobe related to their low variation amplitude. This result is interpretedas being due to the fact that strong stellar pulses lead to thedevelopment of the inner envelope layers, where, from radiative pumpingmodels and VLBI observations, the SiO maser emission arises.
| Detection of new southern SiO maser sources associated with Mira and symbiotic stars
In July 1987 the Parkes radio telescope was used to search for 43.12 GHzSiO maser emission from southern late-type stars. The discovery of suchemission from 12 Mira-like systems, including the symbiotic star H1-36is reported, and the implications of the data for the symbiotic starsare discussed. Several M-type Mira variables with unusually lowSiO/infrared flux ratios are identified. In addition, profiles arepresented for the only other known symbiotic maser, R Aqr, atunprecedented signal-to-noise ratio; these profiles show linearlypolarized emission from several components of the source. In conjunctionwith previous work, constraints are placed on the orbital dynamics ofthe masing component in RAqr.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Phoenix |
| Right ascension: | 23h59m04.57s |
| Declination: | -56°34'32.3" |
| Apparent magnitude: | 7.764 |
| Distance: | 254.453 parsecs |
| Proper motion RA: | 5.9 |
| Proper motion Dec: | -13.2 |
| B-T magnitude: | 9.39 |
| V-T magnitude: | 7.899 |
Catalogs and designations:
|
