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Searching for evidence of interaction between the Of star HD 229196 and the interstellar medium
Massive stars with strong stellar winds are expected to have a hugeimpact on their interstellar surroundings, an effect which, in asurprisingly large number of cases, is not observed. This work is partof a concerted effort to obtain a better and more homogeneousobservational data base with which to test the predictions oftheoretical models. Analysis of the interstellar medium around the Ofstar HD 229196 shows that it coincides (in projection) with a region oflower radio continuum emission. This suggests that the star has shapedthe surrounding interstellar medium via its ionizing flux and stellarwind. However, we find no clear evidence of the star's action in atomichydrogen images. The radio continuum morphology and absence of a clearexpanding HI shell are consistent with the possibility that the star,which is travelling supersonically at ~30kms-1 with respectto its local interstellar medium, is creating a weak bow shock. Wecannot however rule out the possibility that the observed asymmetry isdue to an inhomogeneous interstellar density distribution. We use datafrom the Canadian Galactic Plane Survey to carry out this study.
| The CH2CN- molecule: carrier of the λ8037 diffuse interstellar band?
The hypothesis that the cyanomethyl anion CH2CN- isresponsible for the relatively narrow diffuse interstellar band (DIB) at8037.8±0.15 Å is examined with reference to newobservational data. The 0_00 absorption band arising from the^1B_1-tildeX ^1A' transition from the electronic ground state to thefirst dipole-bound state of the anion is calculated for a rotationaltemperature of 2.7 K using literature spectroscopic parameters andresults in a rotational contour with a peak wavelength of 8037.78Å. By comparison with diffuse band and atomic line absorptionspectra of eight heavily-reddened Galactic sightlines, CH2CN-is found to be a plausible carrier of the λ8037 diffuseinterstellar band provided the rotational contour is Doppler-broadenedwith a b parameter between 16 and 33 km s-1 that depends onthe specific sightline. Convolution of the calculated CH2CN-transitions with the optical depth profile of interstellar Ti II resultsin a good match with the profile of the narrow λ8037 DIB observedtowards HD 183143, HD 168112 and Cyg OB2 8a. The rotational levelpopulations may be influenced by nuclear spin statistics, resulting inthe appearance of additional transitions from Ka = 1 of orthoCH2CN- near 8025 and 8050 Å that are not seen incurrently available interstellar spectra. For CH2CN- to bethe carrier of the λ8037 diffuse interstellar band, either a)there must be mechanisms that convert CH2CN- from the orthoto the para form, or b) the chemistry that forms CH2CN- mustresult in a population of K_a'' levels approaching a Boltzmanndistribution near 3 K.
| The Hα stellar and interstellar emission in the open cluster NGC 6910
Aims.We verify the nature of emission-line stars in the field of theopen cluster NGC 6910. Methods: Spectroscopy in the Hα region wasobtained. Raw CCD frames of spectra of all stars fainter than V = 9 magobserved by us are significantly affected by nebular emissionoriginating in the surrounding H II region IC 1318. After careful datareduction and subtraction of the nebular radiation we succeeded inobtaining reliable stellar spectra. Results: We confirm that the starNGC 6910 37 is a Be star, and we have corrected the classification ofV1973 Cyg from an Ae star to a normal A type star. Since the diffuseinterstellar bands do not appear in the spectrum of this star whilebeing present in the other stars we observed, we confirm that V1973 Cygis a foreground object with respect to IC 1318 and NGC 6910. We alsofind that the Hα line in HD 194279 has a P Cygni profile and theHα line profile is variable in HD 229196.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| CHORIZOS: A χ2 Code for Parameterized Modeling and Characterization of Photometry and Spectrophotometry
We have developed CHi-square cOde for parameterRized modeling andcharacterIZation of phOtometry and Spectrophotmetry (CHORIZOS). CHORIZOScan use up to two intrinsic free parameters (e.g., temperature andgravity for stars, type and redshift for galaxies, or age andmetallicity for stellar clusters) and two extrinsic parameters (amountand type of extinction). The code uses χ2 minimization tofind all models compatible with the observed data in the modelN-dimensional (N=1, 2, 3, 4) parameter space. CHORIZOS can use eithercorrelated or uncorrelated colors as input and is specially designed toidentify possible parameter degeneracies and multiple solutions. Thecode is written in IDL and is available to the astronomical community.Here we present the techniques used, test the code, apply it to a fewwell-known astronomical problems, and suggest possible applications. Asa first scientific result from CHORIZOS, we confirm from photometry theneed for a revised temperature-spectral type scale for OB starspreviously derived from spectroscopy.
| A Galactic O Star Catalog
We have produced a catalog of 378 Galactic O stars with accuratespectral classifications that is complete for V<8 but includes manyfainter stars. The catalog provides cross-identifications with othersources; coordinates (obtained in most cases from Tycho-2 data);astrometric distances for 24 of the nearest stars; optical (Tycho-2,Johnson, and Strömgren) and NIR photometry; group membership,runaway character, and multiplicity information; and a Web-based versionwith links to on-line services.
| A CCD Search for Variable Stars of Spectral Type B in the Northern Hemisphere Open Clusters. VI. NGC 6910
We present results of variability search in the field of the young opencluster NGC 6910. We found four beta Cep-type stars in the cluster,which makes it rather exceptional among the northern clusters observedin our project. Two of these beta Cep stars show three modes withamplitudes above the detection level, in the remaining two we detectsingle modes. We discuss the possibility that the large number of betaCep stars in NGC 6910 is due to higher metallicity of the cluster. Inaddition, we found four other variables, one ellipsoidal or eclipsingbinary and three that show irregular variations. The latter three starshave H alpha in emission.We also provide VI_C photometry for 139 stars down to V=16.6 mag and Halpha photometry for 73 stars. Using this photometry we estimate thecluster age to be equal to 6+/-2 Myr, and the distance modulus,11.0+/-0.3 mag. The reddening is high and variable across the cluster.In terms of the E(V-I_C) color-excess it amounts to 1.25-1.7 mag,corresponding to E(B-V) between 1.0 mag and 1.4 mag. The averagereddening in the central field is E(V-I_ C=1.47+/-0.04 mag.
| A study of RV in Galactic O stars from the 2MASS catalogue
We present new measurements of the interstellar reddening parameterRV=AV/E(B-V) towards 185 O stars, using J, H,Ks photometry from the 2MASS project. The results arecombined with data from the literature of 95 stars where RVhas been derived with the same technique, 22 of which in common with ourpresent sample from the 2MASS project catalogue. The averageRV from these 258 O stars is of 3.19 +/- 0.50. All objectswhose RV departs from this value by more than 2 sigma havebeen recognized. Ten objects have RV higher than this valueand two lower. It is found that anomalous RV can scarcely beassociated with anomalies in the general interstellar medium, e.g. withdifferent behaviour in different spiral arms. They are clearly linked tolocal cloud effect. In the Cygnus region RV values follow thebehaviour of the general interstellar medium, while in the Carina arm,in spite of the relatively larger distance, local cloud effects prevail.An explanation for this is suggested. The relatively few stars of oursample whose Hipparcos parallaxes are reliable, are found to havedistances systematically smaller than the distances derived by thespectroscopic parallaxes. We argue that this effect is consistent withthe recently claimed discovery of grey extinction towards OB stars.This publication makes use of data products from the Two Micron All SkySurvey (2MASS), which is a joint project of the University ofMassachusetts and the Infrared Processing and Analysis Center/CaliforniaInstitute of Technology, funded by the National Aeronautics and SpaceAdministration and the National Science Foundation.Tables 1 and 2 are 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/410/905
| The relation between far-UV and visible extinctions
For directions of sufficient reddening (/E(B-V)>~0.25), there is asimple relation between the slope of the extinction curve in the far-UVand /E(B-V). Regardless of direction, the far-UV extinction curve isproportional to 1/λn e-2E(B-V)/λ(/λ in μm, /n=4), in accordance with the idea that reddenedstars spectra are contaminated by scattered light (Zagury, 2001b). Thisrelation is not compatible with the standard theory of extinction whichstates that far-UV and visible extinctions are due to different classesof particle. In that model the two (far-UV and visible) extinctions varythus independently according to the proportion of each type of particle.In preceding papers I have shown that the standard theory cannot explainUV observations of nebulae, and is contradicted by the UV spectra ofstars with very low reddening: for how long shall the standard theory beconsidered as the interpretation of the extinction curve?
| The 76th Name-List of Variable Stars
We present the next regular Name-List of variable stars containinginformation on 1406 variable stars recently designated in the system ofthe General Catalogue of Variable Stars.
| Determination of R_V towards galactic O stars
We present new measurements of the interstellar reddening parameterRV=AV/E(B-V) towards 35 O stars. The results arecombined with measurements from the literature for 60 stars to study thebehaviour of RV with heliocentric distance. RV isthe single basic parameter which characterizes the interstellarextinction from the near-infrared to the far-UV spectral region. Theabsolute extinction AV, from which RV is derived,is best determined by optical and near-infrared photometry (Cardelli etal. \cite{r3}). We consider important the derivation of RVwith the same technique in the direction of as many as possible galacticO stars.
| Coordinated observations of Cyg X-1 (V1357 Cyg) from 1994 1998 in the commonwealth of independent states
We present observations of Cyg X-1 obtained during the coordinatedinternational campaign “Optical Monitoring of Unique AstrophysicalObjects,” carried out in observatories of CIS countries (Georgia,Kazakhstan, Russia, Uzbekistan, and Ukraine) in 1994 1998. The data arepresented as a single set, taking into account systematic differencesbetween individual data sets. In total, 2258 UBVR observations wereobtained during 407 nights. The observations were carried outsimultaneously with X-ray observations at 2 10 keV (ASM/RXTE) and 20 100keV (BATSE/CGRO), and also with radio observations (in 1997). Ouroptical data partially overlap the soft X-ray outburst in 1996 (JD2450200-320) and subsequent hard state, which displayed various types ofincreases and decreases of the X-ray flux. The 1996 outburst was notaccompanied by any optical brightening. However, an orbital light curvecorresponding to a tidally distorted star was superimposed on individualflares and brightness dips. For example, in two independent sets ofobservations, an intense optical flare with amplitude above thequiescent level was detected on JD 2450988, preceding the X-ray flare onJD 2451000-51040. In this time interval, the system displayed chaoticintrinsic variability on a timescale of a day, and flares and brightnessdips with amplitude lasting up to several days. The variability powerspectra display a predominant secondary period at 147d±2d, whichis half the 294d “precessional” period previously found atboth X-ray and optical wavelengths. We show that the 147d perioddominates in X-ray data (ASM/RXTE) in the quiescent state, or aftersubtraction of the 1996 outburst radiation from the X-ray light curve.This period is also close to the period of 142d±7d derived fromrecent radio data. Cross-correlation analysis confirms a significantcorrelation between the long-term optical and 2 10 keV X-ray variations(without the soft X-ray outburst), with the X-ray variations lagging by12±2 days.
| The Search for Interstellar C60
The optical region of a number of reddened O-type stars has beenexamined on Keck I HIRES spectrograms (R=45,000) for evidence ofinterstellar C60. No absorption features were detected nearthe laboratory C60 wavelengths 3857 and 3980 Å. Aninterstellar feature is present at 6220.8 Å, but it isunacceptably far from the laboratory gas-phase wavelength of 6217.5Å. It is probably just another of the weak diffuse interstellarbands (DIBs), which are numerous in that spectral region. The mostastronomically promising C60 feature was measured in thelaboratory at 3284 Å in liquid or solid matrices. Its gas-phasewavelength can be inferred either from matrix shifts of C60features at longer wavelengths or from high-temperature gas-phasemeasurements. On that evidence, the interstellar feature could fallanywhere between about 3244 and 3306 Å. Its width is uncertain buthere is taken to be about 1 Å . No interstellar absorption fittingthese specifications and as strong as 16 mÅ has been detected inthe stars observed, including Cyg OB2/8A of E(B-V)=1.60. It follows thatin that particular line of sight and for the assumed FWHM of 1 Å ,N(C60)<4.5×1011 cm-2. However,some recent laboratory spectroscopy suggests that its width may be verymuch larger, in which case this limit would be invalid. At this upperlimit, the corresponding number of carbon atoms contained in neutralC60 indicates that that molecule would be only a minorcontributor to the total amount of C in that direction, and would beless than 1% of the amount that may be tied up in the DIBs. StrongerC60 bands are known in the laboratory at approximately 2110and 2566 Å, but the upper limit on 3284 Å suggests that theywill not be easy to detect without high resolution, high signal-to-noiseratio (S/N) satellite spectroscopy and better laboratory gas-phasewavelengths. An estimate of the column density ofC+60, under the assumption that the 9577, 9632Å bands are indeed due to C+60 and that thelaboratory f-value is correct, indicates that theC+60/C60 abundance in that line ofsight is greater than 100.
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Search for Pre-Main-Sequence Stars in the Young Galactic Cluster NGC 6910
Photometric CCD UBV measurements have been obtained in the field of theyoung Cygnus cluster NGC 6910. The observations reach down to magnitudeV~=18 for 206 stars measured in all three UBV bands, uncovering theregion of the color-magnitude diagram where pre-main-sequence (PMS)stars are expected. The transformation of our instrumental magnitudes tothe standard system is discussed on the basis of two different sets ofstandard stars: 22 stars from six fields in the Landolt catalogs and 48stars with published photoelectric photometry in common with ours in thefour clusters observed in this campaign. The latter set is preferred,since it enables the effect of systematic errors in the U-B colors to beminimized. The adopted cluster parameters are E(B-V)=1.02+/-0.13,V0-MV=11.2+/-0.2, and age=(6.5+/-3)x106yr. The search for PMS cluster members on the basis of the calculatedcolor excess and distance modulus results in the proposed membership for11 PMS stars of spectral types from A to G.
| Variability of Cyg X-1 (V1357 Cyg) in 1995-1996 during the Hard and Soft X-ray Spectral States
We report photoelectric UBVR observations of Cyg X-1 with the 1-mTien-Shan and 48-cm Mount Maidanak reflectors from October 1995 throughNovember 1996. The orbital light curve is represented by the model of atidally deformed star. Various types of flare and fading are observed.The optical and X-ray (ASM/RXTE 2-10 keV) variabilities are compared. A90-day soft X-ray outburst occurred in the summer of 1996, but nosimilar event was detected at optical wavelengths. Nevertheless, aninterrelation was found between the variabilities in these bands,suggesting that they are affected by the same processes. A correlationbetween changes in the mean X-ray and optical fluxes was found after the90-day X-ray outburst and the mean optical orbital light curve weresubtracted. A Fourier analysis reveals common features in Fourierspectra of the X-ray and optical data. An orbital X-ray variability witha 5.6-percent amplitude is confirmed. Optical flares with a 0.04-magamplitude and a duration of several days, which coincided with localX-ray minima, were detected. The optical brightness of Cyg X-1 declinedby 0.04-mag in about a week early in November 1996. A possible physicalinterpretation of the flares and the orbital X-ray variability in termsof accretion instability is offered. The characteristic time it takesfor matter to pass through the accretion structure is estimated directlyfrom observations; it was approximately a week in 1996.
| New Observations of the Fuor V1057 Cyg
Not Available
| A study of the open cluster NGC 6811
We made 191 radial-velocity measurements for 60 late-type stars in awide field of the open cluster NGC 6811 using a correlationspectrometer. Based on the similarity of their mean radial velocities(V_r) to the cluster velocity, we identified seven new members within 35arcmin of the cluster center. Photoelectric UBVRI magnitudes weremeasured for 117 probable cluster members as identified by their propermotions (Sanders 1971). We refined the distance to the cluster (1040 pc)and estimated its age (7 x 10^8 years). Using the photometric data, weconfirmed the cluster membership for 88 stars.
| 1-m spectroscopy of normal OB stars
We have obtained spectra of 70 normal OB stars in the near-IR I(1-μm) band. The strongest features are those due to lines of thehydrogen Paschen series and neutral and ionized helium, which are, forthe most part, in absorption. The information content in this spectralrange is sufficient for only a rough classification of hot stars into`early O', `late O' and `B' types. Curiously, the leading He i tripletline, He i λ1.0830 μm, is usually not detectable, although ina few stars it is in emission; its behaviour generally correlates withthe leading helium singlet line, He i λ 2.058 μ m. These twofeatures appear to be present in emission only in stars with extremes ofmass loss or wind extension.
| 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.
| Accurate Two-dimensional Classification of Stellar Spectra with Artificial Neural Networks
We present a solution to the long-standing problem of automaticallyclassifying stellar spectra of all temperature and luminosity classeswith the accuracy shown by expert human classifiers. We use the 15Angstroms resolution near-infrared spectral classification systemdescribed by Torres-Dodgen & Weaver in 1993. Using the spectrum withno manual intervention except wavelength registration, artificial neuralnetworks (ANNs) can classify these spectra with Morgan-Keenan types withan accuracy comparable to that obtained by human experts using 2Angstroms resolution blue spectra, which is about 0.5 types (subclasses)in temperature and about 0.25 classes in luminosity. Accuratetemperature classification requires a hierarchy of ANNs, whileluminosity classification is most successful with a single ANN. Wepropose an architecture for a fully automatic classification system.
| Constraints on the properties of the 2175Å interstellar feature carrier.
Constraints on the possible shape and clustering, as well as opticalproperties, of grains responsible for the 2175Å interstellarextinction feature (interstellar UV bump) are discussed. Theseconstraints are based on the observation that the peak position of theinterstellar UV feature is very stable (variations <~1%), that thelarge variations in width (<~25%) are uncorrelated with the peakposition except for the widest bumps, and that the shape of the featureis described extremely well by a Drude profile. The UV extinction ofsmall graphite grains is computed for various clustering modelsinvolving Rayleigh spheres. It is shown that compact clustersqualitatively satisfy the above observational constraints, except thatthe peak position falls at the wrong wavelength. As an alternative tographite to model the optical properties of the interstellar UV featurecarrier, a single-Lorentz oscillator model is considered, in conjunctionwith a clustering model based on clusters of spheres. Intrinsic changesin the peak position and width are attributed to variations in chemicalcomposition of the grains, impacting upon the parameters of the Lorentzoscillator. Further broadening is attributed to clustering. These modelsare shown to satisfy the above observational constraints. Furthermore,the correlated shift of peak position with increased width, observed forthe widest interstellar UV features, is reproduced. Models involving asecond Lorentz oscillator to reproduce the FUV rise are also considered.The impact of this extra Lorentz oscillator on the peak position, width,and shape of the bump is investigated. Synthetic extinction curves aregenerated to model actual ones exhibiting a wide range of FUVcurvatures. Physical mechanisms which might be of relevance to explainthe variations of these optical properties are discussed.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| Observations of FU Orionis objects: the bank of Maidanak photoelectric observations of V1057 Cygni, V1515 Cygni, and FU Orionis.
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.
| 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 Diffuse Interstellar Bands
The diffuse interstellar bands are absorption features observed in thespectra of stars seen through significant column densities ofinterstellar material. Of the 127 confirmed DIBs in the optical regionbetween 0.4 and about 1.3 $\mu$m, only 2 have (tentatively) beenidentified with a specific carrier. Because DIB strengths increaseroughly in proportion to color excess, they were originally suspected ofbeing produced on or in the interstellar grains, but current evidencefavors some species of free polyatomic molecules, either neutral orionized. DIBs are conspicuously broader than the atomic interstellarlines, having widths at half-depth ranging from 0.8 to about 30 \AA.These widths are presumably due to unresolved rotational structure,possibly compounded by lifetime broadening of the upper state. Recentproposals that C60, some members of the PAH family, or polycarbon chainsare responsible for the DIB spectrum are either not supported byobservation or await better data.
| Rnu-dependent optical and near-ultraviolet extinction
We have derived extinctions A(lambda)/A(V) at the wavelengths of theuvby filters for 22 stars, with a range of values of Rnu,from the sample of Cardelli, Clayton, & Mathis (1989, hereafterCCM). We have fit these extinctions, and also UBVRIJHKL, IUE and ANSextinction measurements, with linear relations A(lambda)/A/(V) =a+b/Rnu and fit a and b as a function of x(=1/lambda) withpolynomials to obtain an Rnu-dependent mean extinction law(A(x)/A(V) = a(x) + b(x)/Rnu)in the optical andnear-ultraviolet (1.1/micrometer less than or equal to 3.3/micrometer).This law is virtually identical to the CCM extinction law for largevalues of Rnu(Rnu approximately 5) but is slightlylower in the near-ultraviolet for smaller Rnu (Rnuapproximately 3). The extinction law presented here agrees much betterwith a high-resolution extinction curve for the diffuse interstellarmedium (Rnu approximately 3.1), presented by Bastiaansen(1992), than CCM. The deviations of individual extinction curves fromthe mean are dominated by observational errors. The wavelengthresolution of this work is not high enough to show evidence for oragainst the existence of very broad structure in optical extinctioncurves.
| The Diffuse Ionized Interstellar Medium: Structures Resulting from Ionization by O Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...417..579M&db_key=AST
| Anomalous Proper-Motions in the Cygnus Super Bubble Region
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..101...37C&db_key=AST
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