New runaway OB stars with HIPPARCOS
A Monte Carlo method for detection of runaway OB stars fromobservational data is proposed. 61 runaway OB star candidates have beendetected by an analysis of Hipparcos proper motions. The peculiartangential and total transverse velocities have been determined forthese stars. A list of the detected runaway star candidates ispresented. The evidence of a discrepancy between photometric andparallactic distances of runaway OB star candidates is presented.
|
A search for nonthermal radio emission from OB and WR stars with RATAN-600
We have searched for nonthermal radio emission from 40 OB and WR stars.Enhanced nonthermal radio emission from an early-type star could beevidence for the presence of a collapsed companion, and thus for itsorigin as the result of a supernova explosion in a massive binary. Asshown in the evolutionary calculations of joint evolution of a neutronstar and a normal star in binaries (Lipunov & Prokhorov \cite{lp}),a considerable fraction of neutron stars in binary systems having anoptical companion must be in the ejector state. A neutron star in thisstate generates a relativistic wind like an isolated radio pulsar. Mostejectors in binary systems can not be identified as radio pulsarsbecause of absorption of radiowaves in the stellar wind of the normalcompanion, but instead, they may appear as sources of high-energy quantadue to the synchrotron radiation of relativistic particles (ejected bythe radio pulsar) in the magnetic field of a normal star (Lipunov &Prokhorov \cite{lp2}; Lipunov & Nazin \cite{naz}). In this case asource of nonthermal radiation in a wide range from radio to hardgamma-ray may appear as a result of a specific reflection effect in themagnetic field of the optical companion. Cyg X-3 and the periodicradioburster LS I +610303 may be examples of just this kind.To test this idea, measurements of radio flux densities in the rangefrom 0.96 to 21.7 GHz from selected OB and WR stars were made with theRATAN-600. No nonthermal radio emission from the selected stars weredetected.
|
ORFEUS II echelle spectra: The scale height of interstellar O VI in the halo
FUV high resolution spectra of 18 stars, particularly chosen to observethe interstellar medium (ISM), were obtained during the secondORFEUS-SPAS free flight space shuttle mission in December 1996. Amongthese were 6 objects with a distance to the galactic plane larger than 1kpc, one SMC and 4 LMC stars. This selction of targets is part of theORFEUS program to explore the galactic halo. As the most importanttracer of the hot gas we analyzed the stronger component of theimportant O vi\ doublet in all our ISM spectra. We found an average N(Ovi)x sin |b| of ~ 3.5 x 10(14) cm(-2) on the lines of sight to the 4 LMCstars. Assuming an exponential distribution of O vi\ we calculated amidplane density n0 of 2.07(+0.26}_{-0.24) x 10(-8) cm(-3)and a scale height h0 of 5.50(+2.37}_{-2.09) kpc.
|
On Space Velocities of Binary Stars in Which One Component Has Experienced a Supernova Explosion
When one component of an evolved binary loses a significant fraction ofits initial mass in a symmetric supernova explosion but remains bound toits companion, the remnant binary recoils with a velocity that can becomparable to the orbital velocity of the supernova precursor. Thisvelocity is enough to explain the observed peculiar space velocitiesand/or distances from the Galactic plane of most X-ray binaries andbinary OB runaway stars. Some exceptions certainly occur, butuncertainties in estimates of velocities and distances, as well asmechanisms other than a popular asymmetric kick, may be responsible formost of the exceptions.
|
GPM - compiled catalogue of absolute proper motions of stars in selected areas of sky with galaxies.
Not Available
|
A Search for Pulsar Companions to OB Runaway Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...461..357S&db_key=AST
|
DO OB Runaway Stars Have Pulsar Companions?
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111.1220P&db_key=AST
|
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.
|
Runaway stars from young star clusters containing initial binaries. II - A mass spectrum and a binary energy spectrum
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990AJ.....99..608L&db_key=AST
|
Estimation of the equivalent width of the interstellar CA II K absorption line
Literature values for the equivalent width of the interstellarabsorption line of Ca II K (3933 A) are used to constrain a simpleempirical model for the strength of this line as a function of distancefrom the galactic plane. The best-fit model has an integrated Ca II Kequivalent width in the direction perpendicular to the galactic plane ofapproximately 200 mA and a 'scale height' of approximately 1100 pc. Sucha model is useful for estimating (and correcting for) the contributionof the interstellar Ca II K feature to the total observed Ca II K linestrength in the spectra of metal-deficient stars in the galactic halo.
|
Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
|
The density distribution of refractory elements away from the Galactic plane
The density distributions of the three refractory elements Ti II, Ca II,and Fe II away from the Galactic plane are compared with thedistribution of hydrogen and dust by examining plots of N s in b versusz. It is found that Ti II and Ca II are considerably more extended in zthan the H I and dust and that Fe II has an intermediate extension.Although the results are strongly influenced by sample bias, theindicated exponential scale heights for the data sample are h(Ti II) notless than 2 kpc, h(Ca II) = 1 kpc, h(Fe II) = 0.5 kpc, H(H I) = 0.3 kpc,and h(E/B-V) = 0.1 kpc. Furthermore, it is demonstrated that Ti II andCa II are much more smoothly distributed in space than the hydrogen ordust. The large scale heights for Ti II and Ca II and their smoothdistributions are most easily understood as the effect of a mixturealong the line of sight of two H I phases namely, a diffuse cloud phase,in which nearly all of the Ti and Ca are tied up in dust, and anintercloud medium, where refractory elements are less depleted. It isfound that Ti II and Ca II mostly trace the smoothly distributedintercloud medium. The smoothness of the distributions of Ti II and CaII makes them candidates for use as distance indicators.
|
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.
|
The binary frequency and origin of the OB runaway stars
A radial velocity survey of the bright northern OB runaway stars hasbeen undertaken to determine the frequency of binary stars in thishigh-velocity group. A total of 634 high-dispersion spectrograms of 36proposed runaway stars were obtained over a two year period.Approximately half of the stars are velocity-variable; these includeseven spectroscopic binaries, one possible beta-Cephei variable, and 10stars with emission lines in their spectra. The latter group containsseven of the eight Be stars observed and three luminous O stars, and itis argued that their variability is caused by nonradial pulsation.Fifteen of the program stars have a peculiar radial velocity greaterthan 30 km/s; five others are probable runaways on the basis of distancefrom the galactic plane and proper motion. Only two of the confirmed andprobable runaways, HD 3950 and HD 198846 (Y Cyg), are binaries, and bothare double-lines systems. New orbital elements are presented for HD 3950and the five new binary systems found among the low-velocity stars. Thestatisical methods used to assess velocity variability and periodicsignals are described in detail. The higher fractional abundance ofrunaways among more massive stars, their binary frequency, and theproperties of the runaway binaries suggest that they obtained their highvelocities through single-binary, binary-binary, or n-body closeencounters during the early dynamical evolution of associations.
|
The extent of the local H I halo
Forty-five high-latitude, OB stars have been observed in the Ly alphaand 21 cm lines of HI in an effort to map out the vertical distributionand extent of the local HI halo. The 25 stars for which a reliable HIcolumn density can be obtained from Ly alpha lie between 60 and 3100 pcfrom the plane. The principal result is that the total column density ofHI at an absolute value of z greater than 1 kpc is, on the average, 5 +or - 3 x 10 to the 19th power/sq cm, or 15 percent of thetotalHI. At relatively low z the data toward some starssuggest a low effective scale height and fairly high average foregrounddensity, while toward others the effective scale height is large and theaverage density is low. This can be understood as the result ofirregularities in the interstellar medium. A model with half of the HImass in clouds having radii of a few pc and a Gaussian verticaldistribution with sigma2 = 135 pc, and half of the mass in anexponential component with a scale height of 500 pc, gives asatisfactory fit to the data. The technique of comparing Ly alpha and 21cm column densities is also used to discuss the problem of estimatingthe distance to several possibly subluminous stars.
|
Catalog of O-B stars observed with Tokyo Meridian Circle
A catalog of the O-B stars, selected from 'Blaauw-Parenago' list andRubin's catalog, has been compiled on the FK4 system by the observationsmade with Gautier 8-inch Meridian Circle at the Tokyo AstronomicalObservatory during the period, 1971 to 1979. It contains 1059 stars andwas compiled for the future establishment of high precision propermotions of O-B stars.
|
A catalog of ultraviolet interstellar extinction excesses for 1415 stars
Ultraviolet interstellar extinction excesses are presented for 1415stars with spectral types B7 and earlier. The excesses with respect to Vare derived from Astronomical Netherlands Satellite (ANS) 5-channel UVphotometry at central wavelengths of approximately 1550, 1800, 2500, and3300 A. A measure of the excess extinction in the 2200-A extinction bumpis also given. The data are valuable for investigating the systematicsof peculiar interstellar extinction and for studying the character of UVinterstellar extinction in the general direction of stars for which theextinction-curve shape is unknown.
|
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.
|
The galactic reddening law - The evidence from uvby-beta photometry of B stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&A...142..189T&db_key=AST
|
A search for relativistic companions of runaway OB stars
Recent progress in a search for relativistic companions of OB runawaysis reported. The outcome of spectroscopic studies of four stars isdiscussed: HD 188001 (9 Sagittae), HD 201345, HD 214930, and HD 218915.The spectrum variability and possible periodicity in the measured radialvelocity have been detected for each star, suggesting that these OBstars may indeed have relativistic companions.
|
Search for relativistic companions in 'non-X-ray' binary systems
Guseinov and Zeldovich (1966) have made the suggestion to look forrelativistic objects in close binary systems. Hundreds of strong pointX-ray sources have already been discovered. From up-to-date ideas on theevolution of massive close binary systems it can be inferred that thenumber of relativistic objects which are powerful X-ray sources is about1 percent only of the total number of relativistic objects whichaccompany OB stars. A total of 99 percent of neutron stars and blackholes in massive close binary systems must, therefore, exist in a'nonobservable' form. A study of the OB stars within the Galaxy withrespect to their binary structure is considered as a means for locatingblack holes. The present investigation is concerned with the formulationof criteria which the companions orbiting OB stars would have to satisfyto qualify as relativistic objects rather than normal stars. Attentionis also given to WR stars with probable relativistic companions.
|
Neutral interstellar gas in the lower galactic halo
The optical interstellar absorption lines of Ti II, Ca II, Na I, and the21 cm emission line of H I were observed at high resolution and highdetection sensitivity toward none pairs of nearly aligned distant halostars and foreground disk stars with well determined distances. Analysisof the column densities, velocities, and the directly determinedvariation of the titanium abundances with z-distance leads to a generalpicture of the neutral interstellar material in the lower galactic halo.Two types of gas with distinct distribution, kinematics, and abundancesare found, a thick, low velocity disk (type I) extending from the planeto well beyond the thin disk of OB stars, and a high velocity, much lessstrongly depleted gas (type II) observed only at high z-distances, whichconstitutes at least 24 percent of the mass of the halo gas. Theimplications of this model for the observed neutral gas are discussedboth in terms of the possible origins of the observed gas and in itscomparison with quasi stellar object absorption lines. Previouslyannounced in STAR as N82-29246
|
Meridian observations made with the Carlsberg Automatic Meridian Circle at Brorfelde (Copenhagen University Observatory) 1981-1982
The 7-inch transit circle instrument with which the present position andmagnitude catalog for 1577 stars with visual magnitudes greater than11.0 was obtained had been equipped with a photoelectric moving slitmicrometer and a minicomputer to control the entire observationalprocess. Positions are reduced relative to the FK4 system for each nightover the whole meridian rather than the usual narrow zones. Thepositions of the FK4 stars used in the least squares solution are alsogiven in the catalog.
|
Interstellar titanium abundances toward 19 high-latitude stars
The 3384 absorption line of interstellar Ti II has been observed at highresolution along lines of sight toward nine nearly aligned pairs offoreground disk and background halo stars, the latter having z-distancegreater than 500 pc. The primary result is the great strength of Ti IIabsorption perpendicular to the plane of the Galaxy. Compared with thewell-studied disk abundances, there is apparently a vertical gradient oftitanium depletion above the galactic plane. The gaseous titaniumabundance relative to hydrogen increases with z-distance and with LSRvelocity by factors exceeding 20 and can reach nearly solar proportions.
|
Geneva photometric boxes. II - The reddening towards the galactic poles
It is noted that photometric boxes allow a very accurate estimation ofindividual reddenings for B- and early A-type stars. A catalog of 129stars with galactic latitudes higher than 30 deg is given. A small butsignificant reddening is seen in the direction of both the northern andsouthern galactic poles: E(B-V) approximately 0.04.
|
The Possibility of the Search for Relativistic Objects Using the Ellipsoidal Variability of the Run-Away Stars
Not Available
|
Metal abundances of RR Lyrae stars in galactic globular clusters
Results are reported for image-tube scanner measurements of Preston's(1959) metal-abundance indicator and metallic-line absorption in theG-band region (4285 to 4317 A) of 47 RR Lyrae stars in 12 galacticglobular clusters and 67 RR Lyrae field stars. The relationship (Fe/H)is defined and determined from curve-of-growth analyses of 13 RR Lyraefield stars, while a comparison of metal-abundance vs metallic-lineabsorption relationships derived for the field and cluster starsindicates that both groups can be calibrated in the same way. Based onthis calibration, (Fe/H) values are deduced for the globular-clusterstars and the clusters themselves. It is found that the alpha-richphenomenon is present in these stars and is confined to calcium andtitanium.
|
INHABITED SKY
