Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
3.6 Years of DIRBE Near-infrared Stellar Light Curves
The weekly averaged near-infrared fluxes for 2652 stars were extractedfrom the cold and warm era all-sky maps of the Diffuse InfraredBackground Experiment (DIRBE). Since the DIRBE program only archived theindividual Calibrated Infrared Observations for the 10 month cold eramission, the weekly averaged fluxes were all that were available for thewarm era. The steps required to extract stellar fluxes are described asare the adjustments that were necessary to correct the results forseveral systematic effects. The observations are at a cadence of once aweek for 3.6 years (~1300 days), providing continuous sampling onvariable stars that span the entire period for the longest fundamentalpulsators. The stars are divided into three categories: those with largeamplitude of variability, smaller amplitude variables, and sources whosenear-infrared brightness do not vary according to our classificationcriteria. We show examples of the results and the value of the addedbaseline in determining the phase lag between the visible and infrared.
| The Architecture of the Cassini Division
The Cassini Division in Saturn's rings contains a series of eight namedgaps, three of which contain dense ringlets. Observations of stellaroccultations by the Visual and Infrared Mapping Spectrometer onboard theCassini spacecraft have yielded ~40 accurate and precise measurements ofthe radial position of the edges of all of these gaps and ringlets.These data reveal suggestive patterns in the shapes of many of the gapedges: the outer edges of the five gaps without ringlets are circular towithin 1 km, while the inner edges of six of the gaps are eccentric,with apsidal precession rates consistent with those expected foreccentric orbits near each edge. Intriguingly, the pattern speeds ofthese eccentric inner gap edges, together with that of the eccentricHuygens Ringlet, form a series with a characteristic spacing of 0fdg06day-1. The two gaps with non-eccentric inner edges lie nearfirst-order inner Lindblad resonances (ILRs) with moons. One such edgeis close to the 5:4 ILR with Prometheus, and the radial excursions ofthis edge do appear to have an m = 5 component aligned with that moon.The other resonantly confined edge is the outer edge of the B ring,which lies near the 2:1 Mimas ILR. Detailed investigation of theB-ring-edge data confirm the presence of an m = 2 perturbation on theB-ring edge, but also show that during the course of the CassiniMission, this pattern has drifted backward relative to Mimas.Comparisons with earlier occultation measurements going back to Voyagersuggest the possibility that the m = 2 pattern is actually libratingrelative to Mimas with a libration frequency L ~ 0fdg06 day-1(or possibly 0fdg12 day-1). In addition to the m = 2 pattern,the B-ring edge also has an m = 1 component that rotates around theplanet at a rate close to the expected apsidal precession rate(\dot{?}_B ˜ 5.06° day-1). Thus, the patternspeeds of the eccentric edges in the Cassini Division can be generatedfrom various combinations of the pattern speeds of structures observedon the edge of the B ring: ?_p=\dot{?}_B-jL for j = 1, 2, 3,..., 7. We therefore suggest that most of the gaps in the CassiniDivision are produced by resonances involving perturbations from themassive edge of the B ring. We find that a combination of gravitationalperturbations generated by the radial excursions in the B-ring edge andthe gravitational perturbations from the Mimas 2:1 ILR yields terms inthe equations of motion that should act to constrain the pericenterlocation of particle orbits in the vicinity of each of the eccentricinner gap edges in the Cassini Division. This alignment of pericenterscould be responsible for forming the Cassini-Division Gaps and thusexplain why these gaps are located where they are.
| Long-term photometry and periods for 261 nearby pulsating M giants
We present the results of a 5.5-yr CCD photometric campaign thatmonitored 261 bright, southern, semiregular variables (SRVs) withrelatively precise Hipparcos parallaxes. The data are supplemented withindependent photoelectric observations of 34 of the brightest stars,including 11 that were not part of the CCD survey, and a previouslyunpublished long time-series of VZ Cam. Pulsation periods and amplitudesare established for 247 of these stars, the majority of which have notbeen determined before. All M giants with sufficient observations forperiod determination are found to be variable, with 87 per cent of thesample (at a signal-to-noise ratio of >=7.5) exhibiting multiperiodicbehaviour. The period ratios of local SRVs are in excellent agreementwith those in the Large Magellanic Cloud. Apparent K-band magnitudes areextracted from multiple near-infrared catalogues and analysed todetermine the most reliable values. We review the effects ofinterstellar and circumstellar extinction and calculate absolute K-bandmagnitudes using revised Hipparcos parallaxes.
| A catalogue of multiplicity among bright stellar systems
We consider the multiplicity of stellar systems with (combined)magnitude brighter than 6.00 in Hipparcos magnitudes. We identify 4559such bright systems (including the Sun), and the frequencies ofmultiplicities 1, 2,..., 7 are found to be 2718, 1437, 285, 86, 20, 11and 2. We discuss the uncertainties, which are substantial. We alsoconsider the distributions of periods of orbits and suborbits. We notethat for even more restricted set of 478 systems with VH<= 4.00, the proportions of higher multiples up to sextuple areprogressively larger (213, 179, 54, 19, 8, 5), suggesting substantialincompleteness in even the reasonably well studied larger sample.This sample can be seen as relatively thoroughly studied formultiplicity, and reasonably representative of stars more massive thanthe Sun. But the restriction to VH <= 6 means that oursample contains hardly any systems where all components are low-massmain-sequence stars (K or M).Data on multiplicity are important as a constraint on (i) the starformation problem, (ii) the problem of the evolution of the Galacticstellar population and (iii) the interaction of dynamics and evolutionthrough the effect of Kozai cycles. We discuss these topics briefly.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Period-luminosity relation for M-type semiregular variables from Hipparcos parallaxes
We have studied the period-luminosity (P-L) relationships of oxygen-richsemiregular (SR) variables in several wavelength bands using Hipparcosparallaxes with an accuracy of better than 10 per cent. We have shownthat there is a clear dependence on period of absolute magnitude in theU,B,V,R,IC,J,H,K,L,M,N, [12], [25], [60] and [100] bands, andthat the slope of the linear Mλ- logP relation is asmooth function of wavelength. We point out that this relation can inprinciple be used to derive absolute bolometric magnitude as a functionof period.The behaviour of the second periods of SR variables in the P-L relationin the V and K bands is also discussed.
| Constraining the Lifetime of Circumstellar Disks in the Terrestrial Planet Zone: A Mid-Infrared Survey of the 30 Myr old Tucana-Horologium Association
We have conducted an N-band survey of 14 young stars in the ~30 Myr oldTucana-Horologium association to search for evidence of warm,circumstellar dust disks. Using the MIRAC-BLINC camera on the Magellan I(Baade) 6.5 m telescope, we find that none of the stars have astatistically significant N-band excess compared to the predictedstellar photospheric flux. Using three different sets of assumptions,this null result rules out the existence of the following around thesepost-T Tauri stars: (1) optically thick disks with inner hole radii of<~0.1 AU, (2) optically thin disks with masses of less than10-6 M⊕ (in ~1 μm sized grains) within<~10 AU of these stars, and (3) scaled-up analogs of the solar systemzodiacal dust cloud with more than 4000 times the emitting area. Oursurvey was sensitive to dust disks in the terrestrial planet zone withfractional luminosity oflog(Ldust/L*)~10-2.9, yet none werefound. Combined with results from previous surveys, these data suggestthat circumstellar dust disks become so optically thin as to beundetectable at N band before age ~20 Myr. We also present N-bandphotometry for several members of other young associations and asubsample of targets that will be observed with the Spitzer SpaceTelescope by the Formation and Evolution of Planetary Systems LegacyScience Program. Finally, we present an absolute calibration ofMIRAC-BLINC for four filters (L, N, 11.6, and Qs) on theCohen-Walker-Witteborn system.
| Infrared Colors and Variability of Evolved Stars from COBE DIRBE Data
For a complete 12 μm flux-limited sample of 207 IRAS sources(F12>=150 Jy, |b|>=5deg), the majority ofwhich are AGB stars (~87%), we have extracted light curves in seveninfrared bands between 1.25 and 60 μm using the database of theDiffuse Infrared Background Experiment (DIRBE) instrument on the CosmicBackground Explorer (COBE) satellite. Using previous infrared surveys,we filtered these light curves to remove data points affected by nearbycompanions and obtained time-averaged flux densities and infraredcolors, as well as estimates of their variability at each wavelength. Inthe time-averaged DIRBE color-color plots, we find clear segregation ofsemiregulars, Mira variables, carbon stars, OH/IR stars, and red giantswithout circumstellar dust (i.e., V-[12]<5) and with little or novisual variation (ΔV<0.1 mag). The DIRBE 1.25-25 μm colorsbecome progressively redder and the variability in the DIRBE databaseincreases along the oxygen-rich sequence nondusty slightly varying redgiants-->SRb/Lb-->SRa-->Mira-->OH/IR and the carbon-richSRb/Lb-->Mira sequence. This supports previous assertions that theseare evolutionary sequences involving the continued production andejection of dust. The carbon stars are redder than their oxygen-richcounterparts for the same variability type, except in theF12/F25 ratio, where they are bluer. Of the 28sources in the sample not previous noted to be variable, 18 are clearlyvariable in the DIRBE data, with amplitudes of variation of ~0.9 mag at4.9 μm and ~0.6 mag at 12 μm, consistent with them being verydusty Mira-like variables. We also present individual DIRBE light curvesof a few selected stars. The DIRBE light curves of the semiregularvariable L2 Pup are particularly remarkable. The maxima at1.25, 2.2, and 3.5 μm occur 10-20 days before those at 4.9 and 12μm, and, at 4.9 and 12 μm, another maximum is seen between the twonear-infrared maxima.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| 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
| 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).
| 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
| From Amateur Astronomer to Observatory Director: The Curious Case of R. T. A. Innes
Robert Innes was one of a select band of amateur astronomers who madethe transition to professional ranks towards the end of the nineteenthcentury. Initially he had a passion for mathematical astronomy, butafter settling in Sydney he developed a taste for observationalastronomy, specialising in the search for new double stars. He quicklybecame known for his success in this field and for his publications onsolar system perturbations, and with John Tebbutt's patronage managed tosecure a clerical position at the Royal Observatory, Cape of Good Hope.Once there he continued to observe in his spare time and to publish,and, with strong support from Sir David Gill, was appointed foundingDirector of the Transvaal Observatory. By the time he died in 1933,Innes had received an honorary D.Sc. from Leiden University, and hadestablished an international reputation as a positional astronomer. Thispaper provides an interesting case study of a well-known`amateur-turned-professional', and an example of the ways in whichpatronage played a key role in nineteenth and early twentieth centuryAustralian and South African astronomy.
| 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
| The composition and nature of the dust shell surrounding the binary AFGL 4106
We present infrared spectroscopy and imaging of AFGL 4106. The 2.4-5 mum ISO-SWS spectrum reveals the presence of a cool, luminous star(Teff ~ 3750 K) in addition to an almost equally luminous Fstar (Teff ~ 7250 K). The 5-195 mu m SWS and LWS spectra aredominated by strong emission from circumstellar dust. We find that thedust consists of amorphous silicates, with a minor but significantcontribution from crystalline silicates. The amorphous silicates consistof Fe-rich olivines. The presence of amorphous pyroxenes cannot beexcluded but if present they contain much less Fe than the amorphousolivines. Comparison with laboratory data shows that the pure Mg-endmembers of the crystalline olivine and pyroxene solid solution seriesare present. In addition, we find strong evidence for simple oxides (FeOand Al_2O_3) as well as crystalline H_2O ice. Several narrow emissionfeatures remain unidentified. Modelling of the dust emission using adust radiation transfer code shows that large grains (~ 1 mu m) must bepresent and that the abundance of the crystalline silicates is between 7and 15% of the total dust mass, depending on the assumed enstatite toforsterite ratio, which is estimated to be between 1 and 3. Theamorphous and crystalline dust components in the shell do not have thesame temperature, implying that the different dust species are notthermally coupled. We find a dust mass of ~ 3.9 * 10(-2) M_sun expelledover a period of ~ 4 * 10(3) years for a distance of 3.3 kpc. The F-starin the AFGL 4106 binary is likely a post-red-supergiant in transition toa blue supergiant or WR phase. Based on observations with ISO, an ESAproject with instruments funded by ESA Member States (especially the PIcountries: France, Germany, the Netherlands and the United Kingdom) andwith the participation of ISAS and NASA Based on observations collectedat the European Southern Observatory, La Silla, Chile
| Pulsation Modes in Small-Amplitude Red Variable Stars
We have investigated the pulsation modes of small-amplitude redvariables with well-determined periods and accurate Hipparcos parallaxesby comparing observational and theoretical Q-values. In our sample of 13stars, one appears to be pulsating in the third overtone, nine in thefirst or second overtone, and three in the fundamental or firstovertone. This result is consistent with the predictions of recentpulsation models by Xiong et al.
| 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.
| Stellar radii of M giants
We determine the stellar radii of the M giant stars in the Hipparcoscatalogue that have a parallax measured to better than 20% accuracy.This is done with the help of a relation between a visual surfacebrightness parameter and the Cousins (V - I) colour index, which wecalibrate with M giants with published angular diameters.The radii of(non-Mira) M giants increase from a median value of 50 R_Sun at spectraltype M0 III to 170 R_Sun at M7/8 III. Typical intermediate giant radiiare 65 R_Sun for M1/M2, 90 R_Sun for M3, 100 R_Sun for M4, 120 R_Sun forM5 and 150 R_Sun for M6. There is a large intrinsic spread for a givenspectral type. This variance in stellar radius increases with latertypes but in relative terms, it remains constant.We determineluminosities and, from evolutionary tracks, stellar masses for oursample stars. The M giants in the solar neighbourhood have masses in therange 0.8-4 M_Sun. For a given spectral type, there is a close relationbetween stellar radius and stellar mass. We also find a linear relationbetween the mass and radius of non-variable M giants. With increasingamplitude of variability we have larger stellar radii for a given mass.
| Supplementary southern standards for UBV(RI)c photometry
We present UBV(RI)c photometry for 80 southern red and blue stars foruse as additional standards. The data are tied to the Johnson UBV andCousins (RI)c systems and extend the range of the available stars forcolor equation determination, especially in (U-B) for blue stars and(V-R) and (V-I) for red stars. Comparisons with published data are madeand particularly good agreement is found with Bessell for the red(Gliese) stars.
| HIPPARCOS Astrometry of Infrared-Selected Sources and the Connection Between Optical and Infrared Reference Frames
Astrometric data from the Hipparcos satellite are reported for theoptical counterparts of 87 bright infrared sources. These sources may beuseful in defining a reference frame for infrared observations. The dataare also useful in studying the locations of circumstellar SiO masers.(SECTION: Stars)
| 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.
| ROSAT X-ray observations of a complete, volume-limited sample of late-type giants.
We have investigated a complete sample of the nearest 39 late typegiants (d<=25pc) for which we have probed the X-ray luminosityfunction with unprecedented sensitivity by deep (3...18ksec) ROSATPSPC-observations in the pointed mode, together with ROSAT All-Skysurvey (RASS) data. We confirm the X-ray dividing line for luminosityclass III giants as proposed by Haisch et al. (1991, 1992) and we findevidence, that essentially all luminosity class III giants withB-V<1.2 or spectral type
| 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.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| The general catalogue of trigonometric [stellar] paralaxes
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.
| Non-thermal radio emission from post-main-sequence stars
The Australia Telescope Compact Array (ATCA) has been used to make4.8-GHz observations of 24 fields containing post-main-sequence stars.These stars were selected from a sample of late-type (spectral types G,K and M) giants and bright giants within 30 pc claimed by Slee et al.,from observations with the Parkes radio telescope, to be variablenon-thermal radio emitters. No significant 4.8-GHz radio emission wasdetected from these stars. Non-detection of any stars with the ATCA isan improbable result, and calls for a re-analysis of the original Parkes8.4-GHz observations. A re-analysis suggests that the majority of theclaimed Parkes detections with S less than about 8 mJy are false. Thefive claimed Parkes detections with S greater than 8 mJy are discussedindividually on the basis of the ATCA and Molonglo Observatory SynthesisTelescope (MOST) observations. It is concluded that the Parkes, ATCA,and MOST observations do not invalidate the concept of a 'coronalboundary line' between stars exhibiting chromospheric and coronalemission, and more evolved stars displaying only cool winds.
| 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
| 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.
| On the calibration of the IRAS low-resolution spectra
The need for corrections to the LRS spectra based on a study of a numberof normal stars observed by IRAS is discussed. The spectra of brightstars, such as alpha CMa, were found to be inconsistent with blackbodysources, this effect being generally observed in sources earlier thanabout K3. An attempt is made to correct the LRS spectra by changing theblackbody calibration temperature for Alpha Tau, assumed to be a10,000-K blackbody source for the original LRS flux calibration. It isfound that an anomalously low color temperature must be assumed foralpha Tau to produce reasonable results for earlier-type stars.Corrections based on a set of stars with well-determined effectivetemperatures are examined, as are the resulting color temperatures for72 stars with Atlas spectra.
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Sinek |
| Sað Açýklýk: | 12h17m34.28s |
| Yükselim: | -67°57'38.6" |
| Görünürdeki Parlaklýk: | 4.176 |
| özdevim Sað Açýklýk: | -230.4 |
| özdevim Yükselim: | -25.5 |
| B-T magnitude: | 6.059 |
| V-T magnitude: | 4.332 |
Kataloglar ve belirtme:
|
INHABITED SKY
