Оглавление
Изображения
Загрузить ваше изображение
DSS Images Other Images
Публикации по объекту
A High-Resolution Spectral Atlas of α Persei from 3810 to 8100 Å
We present a high-resolution (λ/δλ=90,000) spectralatlas of the F5 Ib star α Per covering the 3810-8100 Åregion. The atlas, based on data obtained with the aid of the echellespectrograph BOES fed by the 1.8 m telescope at Bohyunsan Observatory(Korea), is the result of the co-addition of a few well-exposed spectra.The final signal-to-noise ratio is ~800 at ~6000 Å. The atlas iscompared with a synthetic spectrum computed using a code based on Kuruczsoftware and databases. The adopted model atmosphere parameters areTeff=6240+/-20 K, logg=0.58+/-0.04, andvmicro=3.20+/-0.05 km s-1. We also derived an ironabundance of [Fe/H]=-0.28+/-0.06. The spectral lines of α Per havebeen identified by matching the synthetic spectrum with the observedone. The atlas is presented in figures and available in digital form onthe World Wide Web, along with the synthetic spectrum and spectral lineidentification tables.Based on data collected with the 1.8 m telescope at Bohyunsan OpticalAstronomy Observatory, South Korea.
| Study of a sample of periodically variable B-type supergiants
One of the pleasing results obtained from the ESA HIPPARCOS spacemission was the discovery of a large number of new B-type variables. Wewere involved in their classification and found some 30 new B-typesupergiants with alpha Cyg-like behaviour. The most natural way ofexplaining this kind of variability is oscillations (see\citet{waelkens1998}). As a follow-up project, we havegathered high-resolution spectroscopic data including the H, He and Silines for most of these targets. Our aim was to determine from theselines their basic stellar parameters, such as effective temperature,gravity, luminosity, helium abundance and wind characteristics withunprecedented accuracy. For this purpose we use the method of lineprofile fitting based on the NLTE atmosphere and line formation codeFASTWIND (see \citet{puls2005}). Once the parameters are fixed, we willsearch for correlations among them to help reveal more about thevariability mechanism and we will deduce a new calibration for thestellar parameters of galactic B-type supergiants.
| Resolving the Effects of Rotation in Altair with Long-Baseline Interferometry
We report the successful fitting of a Roche model, with a surfacetemperature gradient following the von Zeipel gravity darkening law, toobservations of Altair made with the Navy Prototype OpticalInterferometer. We confirm the claim by Ohishi et al. that Altairdisplays an asymmetric intensity distribution due to rotation, the firstsuch detection in an isolated star. Instrumental effects due to the highvisible flux of this first magnitude star appear to be the limitingfactor in the accuracy of this fit, which nevertheless indicates thatAltair is rotating at 0.90+/-0.02 of its breakup (angular) velocity. Ourresults are consistent with the apparent oblateness found by van Belleet al. and show that the true oblateness is significantly larger owingto an inclination of the rotational axis of ~64° to the line ofsight. Of particular interest, we conclude that instead of beingsubstantially evolved as indicated by its classification, A7 IV-V,Altair is only barely off the zero-age main sequence and represents agood example of the difficulties rotation can introduce in theinterpretation of this part of the HR diagram.
| Quantitative spectroscopy of BA-type supergiants
Luminous BA-type supergiants have enormous potential for modernastrophysics. They allow topics ranging from non-LTE physics and theevolution of massive stars to the chemical evolution of galaxies andcosmology to be addressed. A hybrid non-LTE technique for thequantitative spectroscopy of these stars is discussed. Thorough testsand first applications of the spectrum synthesis method are presentedfor the bright Galactic objects η Leo (A0 Ib), HD 111613 (A2 Iabe),HD 92207 (A0 Iae) and β Ori (B8 Iae), based on high-resolution andhigh-S/N Echelle spectra. Stellar parameters are derived fromspectroscopic indicators, consistently from multiple non-LTE ionizationequilibria and Stark-broadened hydrogen line profiles, and they areverified by spectrophotometry. The internal accuracy of the methodallows the 1σ-uncertainties to be reduced to 1-2% in T_effand to 0.05-0.10 dex in log g. Elemental abundances are determined forover 20 chemical species, with many of the astrophysically mostinteresting in non-LTE (H, He, C, N, O, Mg, S, Ti, Fe). The non-LTEcomputations reduce random errors and remove systematic trends in theanalysis. Inappropriate LTE analyses tend to systematicallyunderestimate iron group abundances and overestimate the light andα-process element abundances by up to factors of two to three onthe mean. This is because of the different responses of these species toradiative and collisional processes in the microscopic picture, which isexplained by fundamental differences of their detailed atomic structure,and not taken into account in LTE. Contrary to common assumptions,significant non-LTE abundance corrections of ~0.3 dex can be found evenfor the weakest lines (Wλ 10 mÅ). Non-LTEabundance uncertainties amount to typically 0.05-0.10 dex (random) and~0.10 dex (systematic 1σ-errors). Near-solar abundances arederived for the heavier elements in the sample stars, and patternsindicative of mixing with nuclear-processed matter for the lightelements. These imply a blue-loop scenario for η Leo because offirst dredge-up abundance ratios, while the other three objects appearto have evolved directly from the main sequence. In the most ambitiouscomputations several ten-thousand spectral lines are accounted for inthe spectrum synthesis, permitting the accurate reproduction of theentire observed spectra from the visual to near-IR. This prerequisitefor the quantitative interpretation of intermediate-resolution spectraopens up BA-type supergiants as versatile tools for extragalacticstellar astronomy beyond the Local Group. The technique presented hereis also well suited to improve quantitative analyses of less extremestars of similar spectral types.
| An Improved Infrared Passband System for Ground-based Photometry: Realization
We describe new simulations and field trials of the new infraredpassband system developed and discussed by Young, Milone, & Stagg,who discussed and illustrated the state of infrared photometry andsuggested ways in which it could be improved. In particular, theypresented a new set of passbands that minimize the dependence of thephotometry on the water vapor bands of the atmospheric windows, whichdefined the edges of many previous infrared passbands, especially whenused at sites and under conditions for which they were not designed. Inthis paper, we present numerical simulations for three atmosphericmodels, demonstrate a measure of the signal-to-noise ratio in the newpassbands for these models, and present observational data obtained at arelatively low-elevation site. The latter demonstrate the utility ofthis system for most astronomical sites where photometry can beperformed, and permit the transformation of observations to this system.Publications of the Rothney Astrophysical Observatory, No. 74.
| Atlas and Catalog of Dark Clouds Based on Digitized Sky Survey I
We present a quantitative atlas and catalog of dark clouds derived byusing the optical database ``Digitized Sky Survey I''. Applying atraditional star-count technique to 1043 plates contained in thedatabase, we produced an AV map covering the entire region inthe galactic latitude range |b| ≤ 40°. The map was drawn at twodifferent angular resolutions of 6' and 18', and is shown in detail in aseries of figures in this paper. Based on the AV map, weidentified 2448 dark clouds and 2841 clumps located inside them. Somephysical parameters, such as the position, extent, and opticalextinction, were measured for each of the clouds and clumps. We alsosearched for counterparts among already known dark clouds in theliterature. The catalog of dark clouds presented in this paper lists thecloud parameters as well as the counterparts.
| Forty Years of Spectroscopic Stellar Astrophysics in Japan
The development of Japanese spectroscopic stellar astrophysics in therecent 40 years is reviewed from an observational point of view. In thisarticle, the research activities are provisionally divided into fourfields: hot stars, hot emission-line (Be) stars, cool stars, and otherstars. Historical developments of the observational facilities atOkayama Astrophysical Observatory (spectrographs and detectors) are alsosummarized in connection with the progress in scientific researchactivities.
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 180: zeta Aurigae
Not Available
| Visual Star Colours from Instrumental Photometry
In order to display graphically the visual colours of stars and otherastronomical objects, photometric broadband R, V, B colours are used toproxy for the r, g, b colours of the three visual sensors of the eye.From photometric Johnson B-V and V-R colour indices, R, V, and Bmagnitudes (V = 0) are calculated, and from these the respectivebrightnesses (r, v = 1 = g, and b) are calculated. After suitablenormalization these are then placed in a ternary diagram having r, g,and b as the vertices. All B-V and V-R are adjusted so that the Sunfalls in the same place as a blackbody at 5800 K. The resulting ternaryplot shows all of its objects (stars, planets) in their visual coloursat their relative positions in the ternary diagram. The star coloursdisplayed on a computer monitor screen or as a print with a colourprinter are more vivid than the usual visual impressions of isolatedstars, undoubtedly because of properties of the dark-adapted eye, butdouble-star pairs with contrasting colours correspond nicely totelescopic visual impressions.
| The epoch of the constellations on the Farnese Atlas and their origin in Hipparchus's lost catalogue
Not Available
| Spectral Analysis of 4 Lacertae and ν Cephei
Elemental abundance analysis based on high S/N and high resolutionDominion Astrophysical Observatory spectrograms have been performed fortwo early type supergiants: 4 Lac (B9 Iab) and {\msf ν } Cep (A2 Ia).Lines as weak as of order 5 mÅ are employed in this study. Theprojected rotational velocities of these stars are 14 and 26 kms-1, respectively. Both stars show similar radial velocityamplitudes, macroturbulent velocities and the same general elementalabundance trends. Their He, CNO and light element abundances are solaror overabundant while the iron peak and heavy element abundances aresolar or underabundant. Detailed LTE model atmosphere abundance analysisshows that 4 Lac has nuclearly processed matter in its photosphere while{\msf ν } Cep does not.
| Polarization Effects in the Radiation of Magnetized Envelopes and Extended Accretion Structures
We have calculated the degree and position angle of the polarization ofradiation scattered in a magnetized, optically thin or optically thickenvelope around a central source, taking into account Faraday rotationof the plane of polarization during the propagation of the scatteredradiation and the finite size of the radiation source. The wavelengthdependence of the degree of polarization can be used to estimate themagnetic field of the source (a star, the region around a neutron star,or a black hole), and we have used our calculations to estimate themagnetic fields in a number of individual objects: several hot O andWolf-Rayet stars, compact objects in X-ray close binaries with blackholes (SS 433, Cyg X-1), and supernovae. The spectrum of the linearpolarization can be used to determine the magnetic field in the vicinityof a central supermassive black hole, where the polarized opticalradiation is generated. In a real physical model, this value can beextrapolated to the region of the last stable orbit. In the future, theproposed technique will make it possible to directly estimate themagnetic field in the region of the last stable orbit of a supermassiveblack hole using X-ray polarimetry.
| New Spectral Types L and T
The establishment of new spectral classes cooler than type M has had abrief, yet already rich, history. Prototypes of the new "L dwarf" and "Tdwarf" classes were first found in the late 1980s to mid-1990s, with aflood of new discoveries occurring in the late 1990s with the advent ofdeep, large-area, digital sky surveys. Over four hundred and fifty L andT dwarfs are now cataloged. This review concentrates on thespectroscopic properties of these objects, beginning with theestablishment of classification schemes rooted in the MK Process. Theresulting grid of spectral types is then used as a tool to ferret outthe underlying physics. The temperature ranges covered by these spectraltypes, the complex chemical processes responsible for the shape of theiremergent spectra, their nature as either true stars or brown dwarfs, andtheir number density in the Galaxy are discussed. Two promising avenuesfor future research are also explored: the extension of theclassification system to three dimensions to account for gravity- andmetallicity-dependent features, and the capability of newer large-areasurveys to uncover brown dwarfs cooler than those now recognized.
| Star formation in Sandqvist 187 and 188
We present 1.2 mm continuum data of the filamentary dark cloud Sandqvist187/188 - also known as the Norma cloud - taken with SIMBA (SEST ImagingBolometer Array). The data are complemented by measurements from the2MASS, MSX and IRAS surveys. The extended 1.2 mm emission traces theoptical dark cloud down to a visual extinction of AV = 3.7mag. We derive a mean column density of N(H_2) = 1.4 ×1022 cm-2, equivalent to a visual extinction ofAV = 7.6 mag and a total mass of the cloud of 340 M_ȯ.We also find six compact millimetre sources, labelled MMS 1 to 6, fiveof which coincide with known stellar objects. MMS 6, however, only has avery weak MSX counterpart at 14.56 μm and an absorption feature at8.28 μm consistent with a visual extinction of AV > 145mag. Dust temperatures, luminosities and gas masses for all compactmillimetre sources are given. In an effort to further constrain theuncertain distance to Sandqvist 187/188, we analyse its stellar contentbased on 2MASS colours and find an improved lower limit of 440 ±50 pc.
| CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| Improved Baade-Wesselink surface brightness relations
Recent, and older accurate, data on (limb-darkened) angular diameters iscompiled for 221 stars, as well as BVRIJK[12][25] magnitudes for thoseobjects, when available. Nine stars (all M-giants or supergiants)showing excess in the [12-25] colour are excluded from the analysis asthis may indicate the presence of dust influencing the optical andnear-infrared colours as well. Based on this large sample,Baade-Wesselink surface brightness (SB) relations are presented fordwarfs, giants, supergiants and dwarfs in the optical and near-infrared.M-giants are found to follow different SB relations from non-M-giants,in particular in V versus V-R. The preferred relation for non-M-giantsis compared to the earlier relation by Fouqué and Gieren (basedon 10 stars) and Nordgren et al. (based on 57 stars). Increasing thesample size does not lead to a lower rms value. It is shown that theresiduals do not correlate with metallicity at a significant level. Thefinally adopted observed angular diameters are compared to thosepredicted by Cohen et al. for 45 stars in common, and there isreasonable overall, and good agreement when θ < 6 mas.Finally, I comment on the common practice in the literature to average,and then fix, the zero-point of the V versus V-K, V versus V-R and Kversus J-K relations, and then rederive the slopes. Such a commonzero-point at zero colour is not expected from model atmospheres for theV-R colour and depends on gravity. Relations derived in this way may bebiased.
| A 2dF survey of the Small Magellanic Cloud
We present a catalogue of new spectral types for hot, luminous stars inthe Small Magellanic Cloud (SMC). The catalogue contains 4161 objects,giving an order-of-magnitude increase in the number of SMC stars withpublished spectroscopic classifications. The targets are primarily B-and A-type stars (2862 and 853 objects respectively), with oneWolf-Rayet, 139 O-type and 306 FG stars, sampling the main sequence to~mid-B. The selection and classification criteria are described, andobjects of particular interest are discussed, including UV-selectedtargets from the Ultraviolet Imaging Telescope (UIT) experiment, Be andB[e] stars, `anomalous A supergiants' and composite-spectrum systems. Weexamine the incidence of Balmer-line emission, and the relationshipbetween Hγ equivalent width and absolute magnitude for BA stars.
| Classification of Spectra from the Infrared Space Observatory PHT-S Database
We have classified over 1500 infrared spectra obtained with the PHT-Sspectrometer aboard the Infrared Space Observatory according to thesystem developed for the Short Wavelength Spectrometer (SWS) spectra byKraemer et al. The majority of these spectra contribute to subclassesthat are either underrepresented in the SWS spectral database or containsources that are too faint, such as M dwarfs, to have been observed byeither the SWS or the Infrared Astronomical Satellite Low ResolutionSpectrometer. There is strong overall agreement about the chemistry ofobjects observed with both instruments. Discrepancies can usually betraced to the different wavelength ranges and sensitivities of theinstruments. Finally, a large subset of the observations (~=250 spectra)exhibit a featureless, red continuum that is consistent with emissionfrom zodiacal dust and suggest directions for further analysis of thisserendipitous measurement of the zodiacal background.Based on observations with the Infrared Space Observatory (ISO), aEuropean Space Agency (ESA) project with instruments funded by ESAMember States (especially the Principle Investigator countries: France,Germany, Netherlands, and United Kingdom) and with the participation ofthe Institute of Space and Astronautical Science (ISAS) and the NationalAeronautics and Space Administration (NASA).
| Near-Infrared Molecular Hydrogen Emission from the Central Regions of Galaxies: Regulated Physical Conditions in the Interstellar Medium
The central regions of many interacting and early-type spiral galaxiesare actively forming stars. This process affects the physical andchemical properties of the local interstellar medium, as well as theevolution of the galaxies. We observed near-infrared H2emission lines: v=1-0 S(1), 3-2 S(3), 1-0 S(0), and 2-1 S(1) from thecentral ~1 kpc regions of the archetypical starburst galaxies M82 andNGC 253 and the less dramatic but still vigorously star-forming galaxiesNGC 6946 and IC 342. Like the far-infrared continuum luminosity, thenear-infrared H2 emission luminosity can directly trace theamount of star formation activity because the H2 emissionlines arise from the interaction between hot and young stars and nearbyneutral clouds. The observed H2 line ratios show that boththermal excitation and nonthermal excitation are responsible for theemission lines but that the great majority of the near-infraredH2 line emission in these galaxies arises from energy statesexcited by ultraviolet fluorescence. The derived physical conditions,e.g., far-ultraviolet radiation field and gas density, from [C II] and[O I] lines and far-infrared continuum observations when used as inputsto photodissociation models also explain the luminosity of the observedH2 1-0 S(1) line. The ratio of the H2 1-0 S(1)line to far-IR continuum luminosity is remarkably constant over a broadrange of galaxy luminosities:LH2/LFIR~=10-5, in normallate-type galaxies (including the Galactic center), in nearby starburstgalaxies, and in luminous IR galaxies (LIRGs:LFIR>1011 Lsolar). Examining thisconstant ratio in the context of photodissociation region models, weconclude that it implies that the strength of the incident UV field ontypical molecular clouds follows the gas density at the cloud surface.
| Characteristics and classification of A-type supergiants in the Small Magellanic Cloud
We address the relationship between spectral type and physicalproperties for A-type supergiants in the Small Magellanic Cloud (SMC).First, we construct a self-consistent classification scheme for Asupergiants, employing the calcium K to Hɛ line ratio as atemperature-sequence discriminant. Following the precepts of the `MKprocess', the same morphological criteria are applied to Galactic andSMC spectra, with the understanding that there may not be acorrespondence in physical properties between spectral counterparts indifferent environments. Then we discuss the temperature scale,concluding that A supergiants in the SMC are systematically cooler thantheir Galactic counterparts at the same spectral type, by up to ~10 percent. Considering the relative line strengths of Hγ and the CH Gband, we extend our study to F- and early G-type supergiants, for whichsimilar effects are found. We note the implications for analyses ofluminous extragalactic supergiants, for the flux-weightedgravity-luminosity relationship and for population synthesis studies inunresolved stellar systems.
| Search for magnetic fields in A-type supergiants
We have searched for magnetic signatures in A-type supergiants. Theobtained magnetic values for seven of these stars are presented here.
| High-Resolution Observations of Interstellar Ca I Absorption-Implications for Depletions and Electron Densities in Diffuse Clouds
We present high-resolution (FWHM~0.3-1.5 km s-1) spectra,obtained with the AAT UHRF, the McDonald Observatory 2.7 m coudéspectrograph, and/or the KPNO coudé feed, of interstellar Ca Iabsorption toward 30 Galactic stars. Comparisons of the column densitiesof Ca I, Ca II, K I, and other species-for individual componentsidentified in the line profiles and also when integrated over entirelines of sight-yield information on relative electron densities anddepletions (dependent on assumptions regarding the ionizationequilibrium). There is no obvious relationship between the ratio N(CaI)/N(Ca II) [equal to ne/(Γ/αr) forphotoionization equilibrium] and the fraction of hydrogen in molecularform f(H2) (often taken to be indicative of the local densitynH). For a smaller sample of sight lines for which thethermal pressure (nHT) and local density can be estimated viaanalysis of the C I fine-structure excitation, the average electrondensity inferred from C, Na, and K (assuming photoionizationequilibrium) seems to be independent of nH andnHT. While the electron density (ne) obtained fromthe ratio N(Ca I)/N(Ca II) is often significantly higher than the valuesderived from other elements, the patterns of relative nederived from different elements show both similarities and differencesfor different lines of sight-suggesting that additional processesbesides photoionization and radiative recombination commonly andsignificantly affect the ionization balance of heavy elements in diffuseinterstellar clouds. Such additional processes may also contribute tothe (apparently) larger than expected fractional ionizations(ne/nH) found for some lines of sight withindependent determinations of nH. In general, inclusion of``grain-assisted'' recombination does reduce the inferred ne,but it does not reconcile the ne estimated from differentelements; it may, however, suggest some dependence of ne onnH. The depletion of calcium may have a much weakerdependence on density than was suggested by earlier comparisons with CHand CN. Two appendices present similar high-resolution spectra of Fe Ifor a few stars and give a compilation of column density data for Ca I,Ca II, Fe I, and S I.
| Angular Diameters of Stars from the Mark III Optical Interferometer
Observations of 85 stars were obtained at wavelengths between 451 and800 nm with the Mark III Stellar Interferometer on Mount Wilson, nearPasadena, California. Angular diameters were determined by fitting auniform-disk model to the visibility amplitude versus projected baselinelength. Half the angular diameters determined at 800 nm have formalerrors smaller than 1%. Limb-darkened angular diameters, effectivetemperatures, and surface brightnesses were determined for these stars,and relationships between these parameters are presented. Scatter inthese relationships is larger than would be expected from themeasurement uncertainties. We argue that this scatter is not due to anunderestimate of the angular diameter errors; whether it is due tophotometric errors or is intrinsic to the relationship is unresolved.The agreement with other observations of the same stars at the samewavelengths is good; the width of the difference distribution iscomparable to that estimated from the error bars, but the wings of thedistribution are larger than Gaussian. Comparison with infraredmeasurements is more problematic; in disagreement with models, coolerstars appear systematically smaller in the near-infrared than expected,warmer stars larger.
| Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars
This paper presents the catalogue and the method of determination ofaveraged quadratic effective magnetic fields < B_e > for 596 mainsequence and giant stars. The catalogue is based on measurements of thestellar effective (or mean longitudinal) magnetic field strengths B_e,which were compiled from the existing literature.We analysed the properties of 352 chemically peculiar A and B stars inthe catalogue, including Am, ApSi, He-weak, He-rich, HgMn, ApSrCrEu, andall ApSr type stars. We have found that the number distribution of allchemically peculiar (CP) stars vs. averaged magnetic field strength isdescribed by a decreasing exponential function. Relations of this typehold also for stars of all the analysed subclasses of chemicalpeculiarity. The exponential form of the above distribution function canbreak down below about 100 G, the latter value representingapproximately the resolution of our analysis for A type stars.Table A.1 and its references are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/631 and Tables 3 to 9are only available in electronic form at http://www.edpsciences.org
| STELIB: A library of stellar spectra at R ~ 2000
We present STELIB, a new spectroscopic stellar library, available athttp://webast.ast.obs-mip.fr/stelib. STELIB consists of an homogeneouslibrary of 249 stellar spectra in the visible range (3200 to 9500Å), with an intermediate spectral resolution (la 3 Å) andsampling (1 Å). This library includes stars of various spectraltypes and luminosity classes, spanning a relatively wide range inmetallicity. The spectral resolution, wavelength and spectral typecoverage of this library represents a substantial improvement overprevious libraries used in population synthesis models. The overallabsolute photometric uncertainty is 3%.Based on observations collected with the Jacobus Kaptein Telescope,(owned and operated jointly by the Particle Physics and AstronomyResearch Council of the UK, The Nederlandse Organisatie voorWetenschappelijk Onderzoek of The Netherlands and the Instituto deAstrofísica de Canarias of Spain and located in the SpanishObservatorio del Roque de Los Muchachos on La Palma which is operated bythe Instituto de AstrofÃsica de Canarias), the 2.3 mtelescope of the Australian National University at Siding Spring,Australia, and the VLT-UT1 Antu Telescope (ESO).Tables \ref{cat1} to \ref{cat6} and \ref{antab1} to A.7 are onlyavailable in electronic form at http://www.edpsciences.org. The StellarLibrary STELIB library is also available at the CDS, via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/402/433
| A spectroscopic atlas of Deneb (A2 Iae) lambda lambda 3826-5212
We present a spectroscopic atlas of Deneb (A2 Iae) obtained with thelong camera of the 1.22-m telescope of the Dominion AstrophysicalObservatory using Reticon and CCD detectors. For lambda lambda 3826-5212the inverse dispersion is 2.4 Åmm-1 with a resolutionof 0.072 Å. At the continuum the mean signal-to-noise ratio is1030. The wavelengths in the laboratory frame, the equivalent widths,and the identifications of the various spectral features are given. Thisatlas should provide useful guidance for studies of other stars withsimilar spectral types. The stellar and synthetic spectra with theircorresponding line identifications can be examined athttp://www.brandonu.ca/physics/gulliver/atlases.htmlTable 2 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5), via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/400/1043, or in MS Excel formatvia http://www.brandonu.ca/physics/ gulliver/atlases.html
| Absorption Line Survey of H3+ toward the Galactic Center Sources I. GCS 3-2 and GC IRS3
We present high-resolution (R = 20000) spectroscopy ofH3+ absorption toward the luminous Galactic centersources GCS 3-2 and GC IRS 3. With the efficient wavelength coverageafforded by Subaru IRCS, six absorption lines ofH3+ have been detected in each source from 3.5 to4.0 μm, three of which are new. In particular the 3.543 μmabsorption line of the R(3, 3)l transition arising from themetastable (J, K) = (3, 3) state has been tentatively detected for thefirst time in the interstellar medium, where previous observations ofH3+ had been limited to absorption lines from thelowest levels: (J, K) = (1, 0) of ortho-H3+ and(1, 1) of para-H3+. The H3+absorption toward the Galactic center takes place in dense and diffuseclouds along the line of sight as well as the molecular complex close tothe Ga lactic nucleus. At least four kinematic components are found inthe H3+ absorption lines. We suggestidentifications of the velocity components with those of H I> , CO,and H2CO previously reported from radio and infraredobservations. H3+ components with velocities thatmatch those of weak and sharp CO and H2CO lines areattributed to diffuse clouds. Our observation has revealed a strikingdifference between the absorption profiles of H3+and CO, demonstrating that the spectroscopy of H3+provides information complementary to that obtained from COspectroscopy. The tentative detection of the R(3, 3)l lineand the non-detection of spectral lines from other J > 1 levelsprovide observational evidence for the metastability of the (3, 3)level, which is theoretically expected. This suggests that othermetastable J = K levels with higher J may also be populated.
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| The latitude and epoch for the formation of the southern Greek constellations
Not Available
| JHK Standards for Small Telescopes
The AAVSO Futures meeting, held in Madison, WI, in May 2001, proposedthat the AAVSO support near-infrared research with small telescopes. Aphotometer, the SSP-4, has been developed to provide J- and H-bandcapability for a reasonable cost. However, proper calibrated photometryrequires a set of standard stars. This paper describes such a set ofstars, suitable for small telescopes, and with accurate coordinates,proper motions, and high-quality magnitudes.
|
Добавить новую статью
Внешние ссылки
- - Внешних ссылок не найдено -
Добавить внешнюю ссылку
Группы:
|
Наблюдательные данные и астрометрия
Каталоги и обозначения:
|
