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Search for C2- in Diffuse Clouds
A search has been carried out for the C2- ion indiffuse clouds toward HD 23180, HD 24912, HD 24398, HD 46711, and HD50064 using the HIDES spectrometer on the Okayama 188-cm telescope. Anupper limit of 8.3 × 1010, 1.8 × 1012cm-2 was obtained for the C2- columndensity. The upper limit value (3.8 × 1011cm-2) toward HD 23180 is two orders of magnitude smaller thanthat of the C2 radical. Possible production mechanisms forC2- are discussed.
| 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.
| Some Diffuse Interstellar Bands Related to Interstellar C2 Molecules
We have investigated the correlations between the equivalent widths of21 selected diffuse interstellar bands (DIBs) and the correspondinginterstellar column densities N(C2), N(CN), and N(CH), toward53 stars with color excesses 0.11<=E(B-V)<=1.99. The observationaldata were derived primarily from echelle spectra acquired at R=38,000 aspart of our extensive, continuing survey of the bands. All but six ofthe 53 final spectra show signal-to-noise ratios >=800 at 5780Å. The principal result presented here is that seven of the 21bands prove to be examples of ``the C2 DIBs,'' a class ofweak, narrow bands whose normalized equivalent widthsWλ(X)/Wλ (λ6196) are wellcorrelated specifically with N(C2)/E(B-V) via power laws. Incontrast, the similarly normalized equivalent widths of the 14 other,well-known DIBs analyzed here are uncorrelated, or weaklyanticorrelated, with N(C2)/E(B-V), to within theobservational uncertainties. Thus, the polyatomic molecule(s) presumedto cause these seven C2 DIBs may bear a direct chemicalrelation to C2 that is not shared by the polyatomic moleculesputatively responsible for the other 14 bands. The C2 DIBsalso show positive correlations with N(CN)/E(B-V) and N(CH)/E(B-V) inour particular sample of light paths, although generally with shallowerslopes in the case of N(CN) and with greater scatter in the case ofN(CH). Eleven additional C2 DIBs are also identified but arenot analyzed here. Among the 18 C2 DIBs identified, fourapparently have not been previously detected. The λ4963 band isgenerally the strongest of the 18 C2 DIBs, while theλ4734 band shows the most sensitive correlation withN(C2).Based on observations obtained with the Apache Point Observatory 3.5 mtelescope, which is owned and operated by the Astrophysical ResearchConsortium.
| The total-to-selective extinction ratio determined from near IR photometry of OB stars
The paper presents an extensive list of the total to selectiveextinction ratios R calculated from the infrared magnitudes of 597 O andB stars using the extrapolation method. The IR magnitudes of these starswere taken from the literature. The IR colour excesses are determinedwith the aid of "artificial standards" - Wegner (1994). The individualand mean values of total to selective extinction ratios R differ in mostcases from the average value R=3.10 +/-0.05 - Wegner (1993) in differentOB associations. The relation between total to selective extinctionratios R determined in this paper and those calculated using the "methodof variable extinction" and the Cardelli et al. (1989) formulae isdiscussed. The R values presented in this paper can be used to determineindividual absolute magnitudes of reddened OB stars with knowntrigonometric parallaxes.
| A Critical Examination of the l-C3H-2 Spectrum and the Diffuse Interstellar Bands
It has recently been suggested by J. P. Maier's group that the originband and three vibronic bands of the linear propadienylidene anionl-C3H-2 match the diffuse interstellarbands (DIBs). We have examined the wavelength ranges in question usingdata from our ongoing DIB survey at the Apache Point Observatory. Wefind that the strongest DIB (λ6993) is not an acceptablewavelength match to the origin band ofl-C3H-2, based on high-resolutionlaboratory data. The nondetection of interstellar features correspondingto the K=2<--1 and K=0<--1 branches of paral-C3H-2 also argues against theassignment of λ6993 to the K=1<--0 branch of orthol-C3H-2. Two of the three DIBs thathave been attributed to vibronic bands do not correlate in intensitywith λ6993, providing further evidence against the assignment ofthis set of DIBs to l-C3H-2.
| Rejection of the C-7 Diffuse Interstellar Band Hypothesis
Using the new high-resolution (~8 km s-1) echellespectrograph on the 3.5 m telescope at the Apache Point Observatory, wehave begun a high-sensitivity survey of the diffuse interstellar bands(DIBs) in a large sample of reddened stars. Now that we are 2 years intothis long-term survey, our sample includes over 20 reddened stars thatshow at least one of the DIBs that had been suggested to be caused byC-7, based on the gas-phase measurement of theC-7 spectrum by J. P. Maier's group. Thehigh-quality astronomical data from this larger sample of stars, alongwith the spectroscopic constants from the new laboratory work recentlyreported by Maier's group, have enabled us to examine more carefully theagreement between C-7 and the DIBs. We find thatnone of the C-7 bands match the DIBs in wavelengthor expected profile. One of the DIBs (λ5748) attributed toC-7 is actually a stellar line. The two strongestDIBs attributed to C-7 (λ6270 andλ4964) are not correlated in strength, so they cannot share thesame carrier. On the whole, we find no evidence supporting thehypothesis that C-7 is a carrier of the DIBs.
| Observations of Diffuse Interstellar Bands Attributed to C-7
Recent advances in laboratory gas-phase spectroscopy of large moleculesand their ions permit a direct comparison between the diffuseinterstellar bands (DIBs) and proposed carriers. On the basis ofgas-phase data, Tulej et al. recently suggested that fiveA2Πu<--X2Πgelectronic transitions of the linear carbon-chain anionC-7 match with DIBs. We have obtainedhigh-resolution visible spectra of four reddened stars (HD 46711, HD50064, HD 183143, and Cyg OB2 12) to make a detailed comparison with theC-7 laboratory data. Our data show that three ofthe C-7 bands (000 at 6270.2Å, 310 at 6064.0 Å, and120310 at 4963.0 Å)are in good agreement with DIBs in wavelength and relative intensity. Afourth band (110 at 5612.8 Å) also agrees inintensity but is apparently off by 2 Å in wavelength. All otherlaboratory bands of C-7 are not expected to bedetectable in astronomical spectra with the current level ofsensitivity. The gas-phase spectrum of C-7 agreeswith the DIBs better than that of any previously proposed molecule.However, the question of whether C-7 is a DIBcarrier cannot be definitively answered until (1) better laboratorymeasurements confirm, refute, or explain the wavelength discrepancy forthe 110 band and/or (2) better astronomicalspectra reveal the presence or absence of otherC-7 bands. Based on observations obtained with theApache Point Observatory 3.5 m telescope, which is owned and operated bythe Astrophysical Research Consortium.
| Laser Spectroscopy of the Carbon Chains HC_7H and HC_9H
Strong vibronic bands of the ^3Sigma^-_u<--X^3Sigma^-_g transition ofthe linear triplet radicals HC_7H and HC_9H have been measured in thegas phase by cavity ringdown spectroscopy. The origin band of HC_7H andthe origin and nu_3 bands of HC_9H all exhibit well resolved P and Rbranches. For HC_9H, the origin band is within 1 Å of the diffuseinterstellar band lambda5818, yet insufficiently close for positiveidentification. In both molecules, internal conversion is much morerapid than radiative emission, and fluorescence is not observed. Lowerlimits on the radiationless lifetime of the upper state of the originband are determined to be 0.1 ns for HC_7H and 0.01 ns for HC_9H.Because the origin bands of these two radicals are about equallyintense, it should be possible to detect longer members of the series inthe gas phase.
| 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
| 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.
| A new library of stellar optical spectra
Attention is given to a new digital optical stellar library consistingof spectra covering 3510-8930 R at 11-A resolution for 72 differentstellar types. These types extend over the spectral classes O-M andluminosity classes I-V. Most spectra are of solar metallicity stars butsome metal-rich and metal-poor spectra are included. This new library isquantitatively compared to two previously published libraries. It offersseveral advantages over them: it is photometrically well-calibratedindividually and consistently from star to star. Good temperature andluminosity coverage has been achieved. The incorporation of stars withwell-determined temperature, metallicity, and surface gravity parametersincreases the accuracy of the spectral type assigned to each compositelibrary star.
| Photometry of HD 50064 - A Be supergiant star with a P Cygni profile at H-alpha
Photometric and spectroscopic observations of the B1 Ia star HD 50064(NGC 2301 No. 3) are presented. It is found to be irregularly variableand to possess a P Cygni profile at H-alpha. It is found that the staris probably no an actual cluster member.
| Miscellaneous spectroscopic notes
Results of slit-spectrograph observations are reported for approximately260 stars. The data presented range from recognition of many new Ap, Am,and other unusual stars to H-alpha observations of early-typesupergiants and Be stars. The material discussed was obtained over thepast 40 years at a number of U.S. observatories and at the DominionAstrophysical Observatory in Victoria, B.C.
| The diffuse interstellar bands. VI - New features near 6800 A
A group of about 29 weak lines lying between 6767 and 6862 A has beenfound on high signal-to-noise ratio (S/N) scans of reddened stars. Theyhave been observed in stars between types O3 and A5, do not appear inunreddened stars of those types observed with the same equipment, andstrengthen with icreasing E(B-V). For these reasons, they are believedto be interstellar. Although narrow, they are not perfectly sharp at aresolution of 35,000. Five or six of the stronger features are nearlyuniformly spaced at intervals of 35/cm, which is suggestive of thespacing expected for rotational structure of light hydrides such as CH,NH and OH, but no plausible carrier of those species has beenidentified.
| The interstellar 217 NM band - A third catalogue of equivalent widths
A catalog of equivalent widths of the 217 nm interstellar absorptionband as well as other parameters characterizing the extinction curve inthe ultraviolet has been compiled for 790 O and B stars. A relativelytight correlation between the equivalent width of the 217 nm band andE(B-V) indicates that the absorber of this band is connected with thepopulation of larger interstellar grains responsible for the visualextinction. The parameter characterizing the amount of extinction in thefar UV is only weakly correlated with E(B-V), a result in accord withthe assumption that a second population of very small grains causes therapid increase of the far-UV extinction.
| The diffuse interstellar features at 5780 and 5797 A in star-formation regions
Substantially reddened stars on the Rho Oph and T Cha clouds, as well asindividual hot stars associated with nebulosity in the 5780, 5797 Adiffuse interstellar line region, have been observed. 5780 A is found tobe generally weak, except in Z CMa and stars SR 3 and SR 5 in the RhoOph cloud. The line at 5797 A is weak relative to 5780 A in all of theprogram stars. The suggestion by others that 5780 and 5797 A are due todifferent sources is confirmed. Finally, the implications of theweakness of these bands in regions of high gas and dust density, as wellas an enhanced radiation field due to the presence of recently formedstars, are discussed.
| Statistical Classification of Ultraviolet Stellar Spectra - IUE Satellite - Progress Report
Not Available
| A library of stellar spectra
Spectra for 161 stars having spectral classes O-M and luminosity classesV, III, and I have been incorporated into a library available onmagnetic tape. The spectra extend from 3510 to 7427 A at a resolution ofabout 4.5 A. The typical photometric uncertainty of each resolutionelement in the spectra is on the order of 1 percent while broad-bandvariations are smaller than 3 percent. Potential uses for the libraryinclude population synthesis of galaxies and clusters, tests of stellaratmosphere models, spectral classification, and the generation of colorindices having arbitrary wavelength and bandpass.
| A catalog of selected compact radio sources for the construction of an extragalactic radio/optical reference frame
A catalog of 234 strong compact extragalactic radio sources that displayoptical counterparts is presented. This catalog identifies proposedsources for establishing an almost inertial reference frame againstwhich the motions of the earth, solar system, galactic objects, andspacecraft may be measured. This catalog also defines those sources forwhich precise optical positions should be determined in order to relatethis reference frame with the optical FK 5 fundamental system. Theaccuracy of the radio source positions of these sources is not greaterthan 0.1 arcsec with the majority not greater than 0.01 arcsec. Furtherrefinement to not greater than 0.005 arcsec by future observations isexpected soon.
| New UBVRI photometry for 900 supergiants
A description is presented of the results obtained in connection with asystematic program of supergiant photometry on the Johnson UBVRI system.During the eight years after the start of the program, almost 1000 starshave been observed, about 400 three or more times each. The originalselection of stars used the spectral type catalog of Jaschek et al.(1964) to choose supergiants. Since observations were possible from bothChile and Canada, no declination limits were imposed, and no particularselection criteria were imposed other than to eliminate carbon stars.These are so red as to require enormous extrapolations of thetransformation equations.
| A survey of interstellar neutral potassium. I - Abundances and physical conditions in clouds toward 188 early-type stars
Observations of interstellar absorption in the resonance doublet 7664,7698 A of neutral potassium toward 188 early-type stars at a spectralresolution of 8 km/s are reported. The 7664 A line is successfullyseparated from nearly coincident telluric O2 absorption for all but afew of the 165 stars for which K I absorption is detected, makingpossible an abundance analysis by the doublet ratio method. Therelationships between the potassium abundances and other atomicabundances, the abundance of molecular hydrogen, and interstellarreddening are investigated.
| List of 333 variable, microvariable or suspected variable stars detected in the Geneva photometry
A list is presented of 333 stars, excluded from the GCVS and itssupplements, whose probability of variability ranges from high tocertain. The standard deviations observed in the V magnitude togetherwith the known spectral types, however, only allow speculation as to thetype of variable in question pending supplementary observations whichreveal the individual characteristics of these stars.
| Infrared photometry of southern early-type stars
The paper presents infrared photometry tied to the JHKL (1.2-3.5microns) broadband photometric system for 229 southern early-type stars.To determine data for stars of low reddening intrinsic visual-IR colorindices were used; the E(V-K)/E(B-V) diagram was applied to evaluate theratio of total selective extinction. A mean value of R = 3.12 plus orminus 0.05 was found for stars close to the galactic plane, but a highervalue of R (about 4.0) applies to the Orion and Sco-Oph regions.Infrared two-color diagrams were used to investigate the occurrence ofinfrared excess emission in different classes of shell star; no excesseswere found for supergiants or Of stars. It is concluded that theanomalous position HD 164740 in the two-color diagrams is produced bystrong infrared excess and not by a peculiar extinction law.
| Infrared colors and the diffuse interstellar bands
Broad-band infrared photometric measurements have been gathered for 105stars which exhibit diffuse interstellar bands in their spectra. Allnormal stars obey a single reddening law, and a value of R equal to 3.08+ or - 0.15 is derived. This value is consistent with other recentdeterminations of R. The diffuse band indicators, the central depth ofthe 4430-A feature and the equivalent widths of the 5780-A and 6284-Afeatures, show as large a scatter with the infrared color excesses asthey do with E(B - V). No single-valued relation between the colorexcesses and the diffuse band strengths appears to exist. This castsdoubt on whether dust grains which produce the visual and infraredextinctions are the carriers for the diffuse interstellar features.
| Observations in linearly polarized light of the intensity of the diffuse lam 6180 absorption band in 56 southern O, B and A stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&A....70..195G&db_key=AST
| The correlation of the interstellar extinction law with the wavelength of maximum polarization
Results are reported for IR photometry of 56 southern stars for whichvalues of the wavelength of maximum polarization (lambdamax)are available. Lambdamax is plotted against EV-K/Esub B-V for each star, and previously published IR data are combinedwith these results, bringing the total number of stars for analysis to98. The plots are evaluated separately for a group of 73 stars withapparently normal spectra and a group of 25 stars with spectralpeculiarities associated with circumstellar shells. It is deduced thatthe ratio (R) of total to selective extinction and lambdamaxare related by the formula R = 5.6 times lambdamax (inmicrons). It is concluded that lambdamax is generally a morereliable grain-size parameter than R and that the most reliable methodof determining the visual absorption for individual stars is currentlythe relation AV = 5.6 (lambdamax) E sub B-V.
| Circular polarization observations of the interstellar magnetic field
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJ...208..727M&db_key=AST
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Observation and Astrometry data
| Constellation: | Monoceros |
| Right ascension: | 06h51m34.11s |
| Declination: | +00°17'50.5" |
| Apparent magnitude: | 8.19 |
| Proper motion RA: | 0.1 |
| Proper motion Dec: | 0.3 |
| B-T magnitude: | 9.024 |
| V-T magnitude: | 8.259 |
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