Садржај
Слике
Уплоадјуј своје слике
DSS Images Other Images
Везани чланци
The Abundance of Interstellar Fluorine and Its Implications
We report results from a survey of neutral fluorine (F I) in theinterstellar medium. Data from FUSE were used to analyze 26 lines ofsight lying in both the galactic disk and halo, including lines toWolf-Rayet stars and through known supernova remnants. The equivalentwidths of the fluorine resonance lines at 951.871 and 954.827 Åwere measured or assigned upper limits and combined with a nitrogencurve of growth to obtain F I column densities. These column densitieswere then used to calculate fluorine depletions. Comparisons are made tothe previous study of F I by Federman and coworkers and implications forF I formation and depletion are discussed.
| Supernova remnant S 147 and its associated neutron star(s)
The supernova remnant S 147 harbors the pulsar PSRJ 0538+2817 whose characteristic age is more than an order ofmagnitude greater than the kinematic age of the system (inferred fromthe angular offset of the pulsar from the geometric center of thesupernova remnant and the pulsar proper motion). To reconcile thisdiscrepancy we propose that PSR J 0538+2817 could be the stellarremnant of the first supernova explosion in a massive binary system andtherefore could be as old as its characteristic age. Our proposalimplies that S 147 is the diffuse remnant of the second supernovaexplosion (that disrupted the binary system) and that a much youngersecond neutron star (not necessarily manifesting itself as a radiopulsar) should be associated with S 147. We use the existingobservational data on the system to suggest that the progenitor of thesupernova that formed S 147 was a Wolf-Rayet star (so that thesupernova explosion occurred within a wind bubble surrounded by amassive shell) and to constrain the parameters of the binary system. Wealso restrict the magnitude and direction of the kick velocity receivedby the young neutron star at birth and find that the kick vector shouldnot strongly deviate from the orbital plane of the binary system.
| On the interstellar extinction law toward young stars
We have determined the atomic hydrogen column density N HI toward all ofthe young stars from the Taurus-Auriga-Perseus star-forming complex forwhich the corresponding spectra are available in the Hubble SpaceTelescope archive (nine stars) by analyzing the Lyα line profile.We show that the stars studied, except DR Tau, lie not far from the edgeof the gaseous cloud of the star-forming region closest to us or, moreprecisely, inside the outer H I shell of the cloud. This shell with acolumn density of N HI ≃ 6 × 1020 cm-2 surrounds themolecular gas of the cloud composed of a diffuse component (theso-called diffuse screen) in which dense, compact TMC-1 cores areembedded. The properties of the dust grains toward the stars that lie atthe front edge of the cloud most likely differ only slightly from thoseof the interstellar dust outside star-forming regions. This casts doubton the validity of the hypothesis that the extinction curve toward youngstars has an anomalously low amplitude of the 2175 Åbump—such an extinction curve is observed for the field stars HD29647 and HD 283809 toward which the line of sight passes through theTMC-1 core.
| A photometric pilot study on Sonneberg archival patrol plates. How many ``constant'' stars are in fact long-term variables?
The light curves of 216 arbitrarly chosen field stars and of 23 knownvariables in the Aur/Tau/Ori region were derived (7.8 m ≤ B ≤12.2 m) from scanned, blue-sensitive archival patrol plates, covering atotal of 34 years (1961-1995). We achieved a photometric accuracy of0.07 ... 0.12 mag in spite of rather unfavourable locations of moststars near the plate borders. 17 field stars turned out to be variables,most of them with time scales of 1000-8000 days in the form of slowwaves with amplitudes between 0.1 and 0.3 mag, i.e. below the thresholdof traditional variable searches on photographic plates. About 50% ofthese new long-term variables exhibit drifts indicating periodic orerratic variability at much longer time scales than covered here. Forthe 23 known variables we achieved improvements in their periods andamplitudes and detected long-term variations (drifts, waves) in about50% of them. The above fraction of low-amplitude long-term variablesamong field stars implies that a total of about 45 000 new variablesshould be detectable in the Sonneberg patrol plate archive. They willrepresent a new, hitherto not investigated population of variable starswith a possibly significant impact on our understanding of the stellarinterior and evolution.Tables 2 and 3 are only available in electronic form athttp://www.edpsciences.org
| Intermediate-velocity gas observed towards the Shajn 147 SNR
We present high-resolution spectra (R 3 km s-1) of theinterstellar Na I and Ca II interstellar absorption lines observedtowards 3 early-type stars with distances of 360 to 1380 pc along theline-of-sight towards the 800 pc distant Shajn 147 (S147) SupernovaRemnant (SNR). These data are supplemented with far-UV (912-1180Å) aborption spectra of HD 36665 andHD 37318 recorded with the NASA Far UltravioletSpectroscopic Explorer (FUSE) satellite. The observations revealintermediate-velocity (IV) absorption features at Vhelio =+92 km s-1 towards HD 37318 and atVhelio = -65 and -52 km s-1 towards HD36665, in addition to several other gas cloud components withlower velocity. These IV components can be associated with the expansionof the SNR that has disrupted the surrounding interstellar gas. The IVcomponent at V = +92 km s-1 seen towards HD37318 was detected only in the far-UV lines of Fe II and N II,suggesting that it is composed mainly of warm and ionized gas. The twoIV components observed towards HD 36665 were detectedin Na I, Ca II, N I, N II, O I and Fe II, indicating that it is composedof both neutral and ionized gas shells. Highly ionized gas was detectedin the O VIλ 1032 Å absorption line at V +40 kms-1 towards both stars. This hot and highly ionized gascomponent is characterized by a columnn density ratio of N(C IV)/N(O VI)< 0.27, which is consistent with that predicted by current models ofevolved SNRs. However, we cannot preclude its origin in the interstellarmedium in line-of-sight to S147. Column-density ratios of [Mg/Fe],[Al/Si],[Si/Fe], [N/Fe], [O/Fe] and [Na/Ca] have been derived for the IVgas components detected towards S147. Similar ratios have also beenderived for fast-moving gas observed towards two other SNRs in order togain some insight into the behavior of element abundances in thedisturbed interstellar gas associated with these regions. In all casesexcept for Na and Ca, these elements appear to be present withnear-solar abundance ratios.
| Statistical analysis of intrinsic polarization, IR excess and projected rotational velocity distributions of classical Be stars
We present the results of statistical analyses of a sample of 627 Bestars. The parameters of intrinsic polarization (p*),projected rotational velocity (v sin i), and near IR excesses have beeninvestigated. The values of p* have been estimated for a muchlarger and more representative sample of Be stars (~490 objects) thanpreviously. We have confirmed that most Be stars of early spectral typehave statistically larger values of polarization and IR excesses incomparison with the late spectral type stars. It is found that thedistributions of p* diverge considerably for the differentspectral subgroups. In contrast to late spectral types (B5-B9.5), thedistribution of p* for B0-B2 stars does not peak at the valuep*=0%. Statistically significant differences in the meanprojected rotational velocities (/line{vsin i}) are found for differentspectral subgroups of Be stars in the sense that late spectral typestars (V luminosity class) generally rotate faster than early types, inagreement with previously published results. This behaviour is, however,not obvious for the III-IV luminosity class stars. Nevertheless, thecalculated values of the ratio vt/vc of the truerotational velocity, vt, to the critical velocity forbreak-up, vc, is larger for late spectral type stars of allluminosity classes. Thus, late spectral type stars appear to rotatecloser to their break-up rotational velocity. The distribution of nearIR excesses for early spectral subgroups is bi-modal, the position ofthe second peak displaying a maximum value E(V-L)~ 1 . m 3for O-B1.5 stars, decreasing to E(V-L)~0. m8 for intermediatespectral types (B3-B5). It is shown that bi-modality disappears for latespectral types (B6-B9.5). No correlations were found betweenp* and near IR excesses and between E(V-L) and vsin i for thedifferent subgroups of Be stars. In contrast to near IR excesses, arelation between p* and far IR excesses at 12 mu m is clearlyseen. A clear relation between p* and vsin i (as well asbetween p* and /line{vsin i}/vc) is found by thefact that plots of these parameters are bounded by a ``triangular"distribution of p*: vsin i, with a decrease of p*towards very small and very large vsin i (and /line{vsini}/vc) values. The latter behaviour can be understood in thecontext of a larger oblateness of circumstellar disks for the stars witha rapid rotation. From the analysis of correlations between differentobservational parameters we conclude that circumstellar envelopes forthe majority of Be stars are optically thin disks with the range of thehalf-opening angle of 10degr
| Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
| Rotational Velocity Determinations for 164 Be and B Stars
Rotational velocities, v sin i, have been obtained for 96 Be and 68normal B stars by measurements of the FWHM of the He I lambda-4471 line(for spectral types B0-B4.5) and Mg II lambda-4481 (for types B5-B9.5).The consistency of various published sources is examined. (SECTION:Stars)
| 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.
| An IUE survey of interstellar H I LY alpha absorption. 1: Column densities
We measure Galactic interstellar neutral hydrogen column densities byanalyzing archival interstellar Ly alpha absorption line data toward 554B2 and hotter stars observed at high resolution with the IUE satellite.This study more than doubles the number of lines of sight with measuresof N(H I) based on Ly alpha. We have included the scattered lightbackground correction algorithm of Bianchi and Bohlin in our datareduction. We use the correlation between the Balmer discontinuity(c1) index and the stellar Ly alpha absorption in order toassess the effects of stellar Ly alpha contamination. Approximately 40%of the B stars with measured (c1) index, exhibit seriousstellar Ly alpha contamination. One table contains the derived values ofthe interstellar N(H I) for 393 stars with at most small amounts ofstellar contamination. Another lists the observed values of total N(H I)for 161 stars with suspected stellar Ly alpha contamination and/oruncertain stellar parameters.
| Chemical transitions for interstellar C2 and CN in cloud envelopes
Observations were made of absorption from CH, C2, and CN towardmoderately reddened stars in Sco, OB2, Ceo OB3, and Taurus/Auriga. Forthese directions, most of the reddening is associated with a singlecloud complex, for example, the rho Ophiuchus molecular cloud, and as aresult, the observations probe moderately dense material. When combinedwith avaliable data for nearby directions, the survey provides the basisfor a comprehensive analysis of the chemistry for these species. Thechemical transitions affecting C2 and CN in cloud envelopes wereanalyzed. The depth into a cloud at which a transition takes place wascharacterized by tauuv, the grain optical depth at 1000 A.One transition at tauuv approx. = 2, which arises from, theconversion of C(+) into CO, affects the chemistries for both moleculesbecause of the key role this ion plays. A second one involvingproduction terms in the CN chemistry occurs at tauuv ofapprox. = 3; neutral reactions which C2 and CH is more important atlarger values for tauuv. The transition fromphotodissociation to chemical destruction takes place attauuv approx. = 4.5 for C2 and CN. The observational data forstars in Sco OB2, Cep OB3, and Taurus/Auriga were studied with chemicalrate equations containing the most important production and destructionmechanisms. Because the sample of stars in Sco OB2 includes sight lineswith Av ranging from 1-4 mag, sight lines dominated byphotochemistry could be analyzed separately from those controlled bygas-phase destruction. The analysis yielded values for two poorly knownrate constants for reactions involved in the production of CN; thereactions are C2 + N yields CN + C and C(+) + NH yields all products.The other directions were analyzed with the inferred values. Thepredicted column densities for C2 and CN agree with the observed valuesto better than 50%, and in most instances 20%. When combining theestimates for density and temperature derived from chemical modeling andmolecular excitation for a specific cloud, such as the rho Ophiuchusmolecular cloud, the portion of the cloud envelope probed by C2 and CNabsorption was found to be in pressure equilibrium.
| IUE-IRAS studies of the infrared cirrus
The 60 and 100 micron cirrus emission around 256 lines of sight in theIRAS all-sky survey was measured, and the flux averages were used tostudy the distribution, variations, and correlations of the IRASinfrared cirrus fluxes with various interstellar parameters. It wasfound that the 60 and 100 micron fluxes correlate with the depletion ofSi and show a trend with the depletion of Fe for 51 lines of sighttoward the Galactic halo. No correlation was found with the abundancesof Si, Mn, Fe, S, or Zn or with abundance ratios for the full sample of256 stars. An abundance ratio of about 3 x 10 to the 7th by numberrelative to H was derived from 60 and 100 micron flux ratios and the Hcolumn along the line of sight; this ratio appears to decrease by afactor of 10 into the halo.
| Galactic interstellar abundance surveys with IUE. III - Silicon, manganese, iron, sulfur, and zinc
This paper continues a survey of intestellar densities, abundances, andcloud structure in the Galaxy using the IUE satellite. A statisticaldata set of 223 O3-B2.5 stars is constructed, including 53 stars in theGalactic halo. It is found that S II lines in B stars, of luminosityclasses IV and V, have possible contamination from stellar S II,particular for stars with v sin i less than 200 km/s. The meanlogarithmic depletions are -1.00, -1.19. -0.63, and -0.23 (Si, Mn,Fe,S,Zn). Depletions of Si, Mn, and Fe correlate with the mean hydrogendensity n-bar along the line of sight, with a turnover for n-bar greaterthan 1/cm. Sulfur depletions correlate with n-bar along the line ofsight. The slight Zn depletion correlation also appears to bestatistically insignificant. No correlation of depletion is found withthe physical density derived from H2 rotational states in 21 lines ofsight. Depletion variations in the disk are consistent with a Galacticabundance gradient or with enhanced mean depletions in the anticenterregion.
| Galactic interstellar abundance surveys with IUE. II - The equivalent widths and column densities
This paper continues a survey of interstellar densities, abundances, andcloud structure in the Galaxy, using the International UltravioletExplorer (IUE) satellite. Equivalent widths of 18 ultraviolet resonancetransitions are presented and column densities for Si II, Mn II, Fe II,S II, and Zn II toward 261 early-type stars are derived. Theseequivalent widths and column densities agree within the stated errors ofearlier Copernicus, BUSS, or IUE surveys of Mn II, Fe II, S II, and ZnII for 45 stars in common. The column densities are derived fromsingle-component curves of growth with a common b-value based on that ofFe II and Si II.
| Galactic interstellar abundance surveys with IUE. I - Neutral hydrogen
A survey is initiated of interstellar densities, abundances, and cloudstructure in the Galaxy, using the International Ultraviolet Explorer.From high-resolution (0.1-A) spectra, interstellar column densities arederived toward 244 early-type stars by fitting the damping wings of theLy-alpha absorption line. Published B-V photometry is used to deriveE(B-V) color excesses, stellar distances r, and the mean hydrogendensities, n-bar = N(H I)/r. The data set includes stars out to r = 8.5kpc and E(B-V) = 0.86, with 68 stars in the galactic halo (absolute bgreater than 20 deg). The statistical sample consists of 205 stars oftype O3-B2.5 within 5 kpc (53 stars in the halo). The column densities,log N(H I), range from less than 19.44 per square centimeter for alphaVir to 21.81 for HD 37061. A statistical analysis of the E(B-V)distribution suggests variations in the line-of-sight cloud density andthe mean reddening per cloud.
| Ultraviolet extinction and diffuse band strength correlations
Correlations between UV extinction parameters and diffuse band strengthsare south, using a data base of 50 stars with recently measuredextinction curves. A novel aspect of this study is that the basicdependence of most interstellar parameters on E(B-V) (or, nearlyequivalently, on the total hydrogen column density) has been largelycanceled out. After this cancellation, a weak correlation is foundbetween the 4430 A diffuse band and the 2175 A extinction feature. Noother correlations are found. These results support a molecular originfor the 5780 A and 6284 A bands. It is speculated that the correlationpattern found for the 4430 A band can be explained if this bandoriginates in reactions on disordered grain surfaces.
| Shock processing of interstellar grains
Theoretical and observational evidence is presented that shockprocessing of interstellar dust grains by supernova blast waves affectsboth heavy element depletions and ultraviolet extinction curves. Bycoupling a realistic model of grain sizes and populations with aradiative shock code, significant grain destruction at velocities as lowas 40 km/s is demonstrated. Nonthermal sputtering and grain-graincollisions destroy relatively more large grains than small, and moresilicates than graphite. Consequently, both the 2175 A extinction 'bump'and the far-ultraviolet normalized extinction are increased in strength.Ultraviolet extinction studies with the International UltravioletExplorer of nine stars near three supernova remnants (the MonocerosLoop, Shajn 147, and Vela) exhibit strong 2175 A bumps and normal orhigh far-ultraviolet extinction. Diffuse bands, if they are created bysmall grains, should show little correlation with such activity.
| Further ultraviolet observations of interstellar gas associated with the supernova remnant S 147
UV observations by the IUE were employed to study the supernova remnant(SNR) gas from S 147 by viewing the star HD 37318. Spectra of HD 37318were examined in the 1150-2000 A and 1900-3200 A UV ranges. Comparisonsof the Fe II lines of HD 37318 with previous data on the same line fromHD 36665, behind the same SNR, indicated that the redshifted, highvelocity component of the line observed was part of the SNR gas.Furthermore, the high density electrons detected in the region of thegas in front of HD 37318 suggests that the area is filled with a shockedinterstellar cloud which is not entirely recombined. Depletion of heavyelements in the high velocity gas is indicative of a return to a gasphase through a sputtering process in the shock front, with the heavyelements existing as grains which are not destroyed by the 80 km/sechigh velocity gas.
| High-velocity gas associated with the supernova remnant S147
The star HD 36665 (Ble), which lies behind the old supernova remnantS147, has been observed with the IUE satellite. High-velocityinterstellar absorption components of Fe II, Mg I, Mg II, Al II, C IIand Si II were detected which originate in gas associated with theremnant. No such high-velocity lines were observed in the IUE spectrumof HD 40111 (Bl Ib) which is offset from the remnant. The high-velocityultraviolet lines, together with new ground-based observations ofhigh-velocity Ca II in HD 36665, have been analyzed to determine columndensities and to estimate the physical conditions in the high-velocitygas. The estimated level of depletions in the high-velocity gas issomewhat less than that normally observed in low-velocity interstellargas, suggesting that sputtering of grains has occurred in the shockfront of the supernova remnant.
| Interstellar carbon monoxide in the direction of the supernova remnant S147
The paper examines interstellar carbon monoxide in the direction of thesupernova remnant S147. The electronic bands in the fourth positivesystem of (C-12)(O-16) were detected in absorption in the ultravioletspectrum of the Ble star HD 36665. The line of sight to this star is 1deg away from the center of the supernova remnant S147 and the star liesbehind the remnant. The equivalent widths of seven bands of a transitionof (C-12)(O-16) were measured and a satisfactory fit to a curve ofgrowth can be obtained for a velocity dispersion b = 5.5 plus or minus0.5 km/sec; the bands of (C-13)(O-16) have also been detected in thespectrum of HD 36665.
| High velocity gas associated with supernova remnants
High dispersion International Ultraviolet Explorer spectra of early typebackground stars were obtained. An analysis was made of absorption linesoriginating in gas associated with the remnant S147 and the detection ofgas associated with the remnant IC443. In the star HD 36665 behind S147,high velocity lines and low velocity interstellar CO was detected,probably originating in gas associated with the remnant.
| International Ultraviolet Explorer and the interstellar medium
A summary of observations by the International Ultraviolet Explorer isgiven. Observations of comets, supernovae, planetary nebulae, H IIregions, supernova remnants, QSOs and Seyfert galaxies are reported.Ultraviolet spectra of some of the afore-going are depicted. Thediscovery of hot galactic coronas is noted, and a chart shows z-scaleheights of the galactic coronal gas.
| High-velocity gas in supernova remnants. II. Shajn 147.
Abstract image available at:http://adsabs.harvard.edu/abs/1973ApJ...181..799S
| Photométrie photoélectrique UBV d'étoiles chaudes des "Selected Areas" 40 et 49 situées AU voisinage DU plan galactique
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1...15B&db_key=AST
| Be stars and galactic rotation.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..338C&db_key=AST
| Luminous Stars in the Northern Milky Way
Not Available
| Die galaktischen Emissions-B-Sterne : (Spectralklassifikation, Photometrie, Entwicklung und Verteilung in der Milchstraszenebene)
Not Available
| Catalogue of stellar spectra classified in the Morgan-Keenan system
Not Available
|
Додај нови чланак
Линкови у сродству са темом
Додај нови линк
Чланови следећих група \:
|
Посматрања и Астрометриски подаци
| Сазвежђа: | Бик |
| Ректацензија: | 05h34m39.10s |
| Deклинација: | +28°03'03.8" |
| Apparent магнитуда: | 8.161 |
| Даљина: | 10000000 parsecs |
| Proper motion RA: | -1.7 |
| Proper motion Dec: | -6 |
| B-T magnitude: | 8.451 |
| V-T magnitude: | 8.185 |
Каталог и designations:
|
