Total to Selective Extinction Ratios and Visual Extinctions from Ultraviolet Data
We present determinations of the total to selective extinction ratio R_Vand visual extinction A_V values for Milky Way stars using ultravioletcolor excesses. We extend the analysis of Gnacinski and Sikorski (1999)by using non-equal weights derived from observational errors. We presenta detailed discussion of various statistical errors. In addition, weestimate the level of systematic errors by considering differentnormalization of the extinction curve adopted by Wegner (2002). Ourcatalog of 782 R_V and A_V values and their errors is available in theelectronic form on the World Wide Web.
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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.
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New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
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Ultraviolet Interstellar Linear Polarization. V. Analysis of the Final Data Set
Using recent measurements of ultraviolet interstellar polarization, wehave examined its relationship to ultraviolet extinction and topolarization and extinction measurements in the visible and infrared.The relationship between the relative amount of ultraviolet polarizationand the parameter lambda_max, determined using only visible data, isconfirmed and strengthened, for example, by a tight correlation betweenp(6 mum^-1)/p_max and lambda^-1_max. A good fit to the wavelengthdependence of the polarization from the infrared to the ultraviolet canbe achieved with a five-parameter function combining a power law in theinfrared and a Serkowski-like function in the ultraviolet. Thepolarization efficiency (ratio of polarization to extinction) is less inthe ultraviolet than in the visual, and the ratio of these efficienciesincreases systematically with lambda^-1_max. We relate these effects tosystematic changes in the underlying aligned grain size distribution.The polarization efficiency of the grains causing the 2175 Åextinction bump along most sight lines is so (unusually) small that nostatistically significant polarization feature is detectable in thatwavelength region. Only two of 28 sight lines show a definitepolarization feature. The environments of the two bump sight lines aresimilar but not unique, and the mechanism for producing the polarizationfeature along only these two sight lines is still not known.
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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.
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Ultraviolet Interstellar Linear Polarization. III. Features
Astro-2 has revealed a broad, weak spectral feature in the ultravioletinterstellar linear polarization for two lines of sight, confirming theoriginal detection toward HD 197770 and adding HD 147933--4. These arethe only two polarization features found in some 30 lines of sight nowobserved. Both features are centered close to 2175 Angstroms, theposition of the ubiquitous ultraviolet extinction bump. Twopossibilities are considered for the source of the polarization feature:changes in the mass distribution of the aligned silicate grainsresponsible for the continuum polarization, and alignment of the smallgraphite grains responsible for the extinction bump. While the formerapproach meets with some success for the HD 197770 feature, it is notpossible to produce a feature as clearly peaked as in HD 147933--4. Thecentral wavenumbers and widths of both polarization features correspondclosely to those of the corresponding extinction bump. Taken together,it seems the graphite grains are a more likely source of thepolarization features. Both polarization features have amplitudes thatare very small compared to the amount of excess extinction present inthe 2175 Angstroms bump, implying poor polarization efficiency. Manyother lines of sight have been observed with sufficient signal-to-noiseratios such that features should have been clearly detected if the samepolarization efficiency applied, and so real variations in the alignmentor shape of the grains responsible seem to occur from one line of sightto another. The weak alignment might be caused by unusually lowconcentrations of paramagnetic impurities in rapidly spinning smallgrains.
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Ultraviolet Interstellar Polarization of Galactic Starlight.I.Observations by the Wisconsin Ultraviolet Photo Polarimeter Experiment
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2726A&db_key=AST
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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.
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Ultraviolet interstellar linear polarization. 2: The wavelength dependence
We present new ultraviolet (UV) polarimetry of the well-studiedinterstellar line of sight toward HD 204827 obtained with the FaintObject Spectrograph on Hubble Space Telescope. HD 204827 is of greatinterest because the dust along this line of sight has extremely lowvalues of both lambdamax and RV. Its far-UVextinction is very large, reflecting its small RV value. Inaddition, we reexamine the entire sample of 14 interstellar lines ofsight for which there are now UV polarization data. We find that thepreviously suggested relationship between lambdamax and thewavelength dependence of the polarization in the UV is stronglysupported by the data for this larger sample including HD 204827. Sevenstars with lambdamax greater than or equal to 0.54 micronagree well with an extrapolation of the Serkowski relation into the UVwhile seven stars with lambdamax less than or equal to 0.53micron show polarization in excess of the Serkowski extrapolation(super-Serkowski). However, the division of the observed lines of sightinto Serkowski and super-Serkowski categories is artificial. In fact,the amount of polarization in the UV is correlated with a singleparameter, lambdamax. This may indicate that there is a meaninterstellar polarization law analogous to the mean interstellarextinction law of Cardelli, Calyton, & Mathis which is based onRV. The data are consistent with a linear relationshipbetween 1/lambdamax and rho(UV)/rhomax but moredata are needed to define the functional form. We suggest that theSerkowski and super-Serkowski designations be replaced by high and lowlambdamax which are more physically descriptive. At the sametime, we note that all seven super-Serkowski (low lambdamax)stars lie in a relatively small region of the sky between lII= 90 deg - 150 deg and b = -5 deg - 15 deg. These stars all lie in orbehind a spur of the local Orion spiral arm. Similarly, most of theSerkowski (high lambdamax stars lie in or near theScorpio-Centaurus OB Association. So lines of sight covering largerareas of the sky are needed to test the universality of thelambdamax/UV polarization relationship. The recent discoveryof warm dust near HD 197770 suggests the possibility that a mechanismother than the traditional alignment to the Galactic magnetic field maybe invoked to explain its 2175 A polarization bump.
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The size distribution of interstellar dust particles as determined from polarization: Spheroids
We have determined the size distribution of polarizing interstellar dustgrains based on electromagnetic scattering by spheroidal particles,extending our original work based on infinite cylinders. Shapes andalignment variants included the following: perfectly aligned oblateparticles with axial ratios 1.414:1, 2:1, 4:1, and 6:1, picket fenceprolate particles with axial ratios 2:1 and 4:1, and 2:1 prolateparticles with perfect spinning alignment. Our analysis is based on baresilicate grains. The size distributions found are qualitatively similarto those derived using infinite cylinders. When expressed ascontributions to the total mass, the distributions peak at mean sizeapproximately 0.2 microns and are skewed, with the relative rate ofdecrease to larger and smaller sizes depending on lambda max.Using infinite cylinders, the specific requirement of a reasonable fitin the infrared produces a substantial dip in the mass distribution atapproximately 0.4 microns, hinting at a bimodal mass distribution. Butthis dip is not present when oblate and prolate particles are used. Thisconfirms that the dip is related to the incorrect behavior of scatteringfor infinite cylinders in the long wavelength limit. Fitting HSTultraviolet polarization data beyond 6 microns -1 introducesan additional bump at the small size end (approximately 0.01 microns) ofthe distribution. This unusual feature can be traced to the sudden risein the imaginary part of the refractive index of 'astronomicalsilicate.' When a 'modified astronomical silicate' is used, the size ofthe additional bump is much reduced, if not absent. Based both on thesmoothness of the mass distribution and on the fit to the polarizationcurve, oblate shapes are preferred to prolate. Among the oblates, the6:1 oblate shape gives the most satisfactory result, simply because thewidth of the calculated polarization curve of single-sized 6:1 oblateparticles is the narrowest. Mass distributions from fitting extinctioncurves using aligned spheroids have been determined. They resembleclosely those based on spheres. Polarization to extinction ratios arelarge enough to match the maximum interstellar value for all axialratios and shapes studied, though the most spherical (1.4:1 oblate and2:1 spinning prolate) particles would have to be nearly perfectlyaligned. The birefringence and interstellar circular polarization in theultraviolet are predicted.
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Observations of diffuse interstellar bands and of interstellar polarization
Not Available
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Ultraviolet interstellar polarization observed with the Hubble Space Telescope
We have used the Faint Object Spectrograph of the Hubble Space Telescopeto observe interstellar linear polarization from 1300 to 3300 A in twostars with well-studied interstellar polarization at visible wavelenths.The wavelength dependence of linear polarization declines smoothly withdecreasing wavelength and is devoid of structure associated with theprominent 2175 A absorption bump in the interstellar extinction curve.The data for one star (HD 161056) are consistent with an extrapolationbased on the Serkowski formula of a fit to the ground-based polariztion;the other star (HD 7252) shows excess (super-Serkowski) polarizationrelative to the extrapolation. Out of a total of 10 stars now studied bymeans of spectropolarimetry in the satellite ultraviolet, includingeight obseved with the Wisconsin Ultraviolet Photopolarimeter, five(those of longest lambda max) show Serkowski behavior, andfour others show super-Serkowski behavior; only one (HD 197770) showsevidence for polarization associated with the 2175 A bump. These resultsplace important constraints on the nature of the bump feature.
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Extinction law survey based on UV ANS photometry
The paper presents an extensive survey of interstellar extinction curvesderived from the ANS photometric measurements of early type starsbelonging to our Galaxy. This survey is more extensive and deeper thanany other one, based on spectral data. The UV color excesses aredetermined with the aid of 'artificial standards', a new techniqueproposed by the authors which allows the special check of Sp/L match ofa target and the selected standard. The results indicate that extinctionlaw changes from place to place.
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A list of MK standard stars
Not Available
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The variation of interstellar extinction in the ultraviolet
One hundred and fifty-four reddened stars that are apparently normal inthe visible were selected from the S2/68 Ultraviolet Sky Survey. Theultraviolet data for 92 of these cannot be explained in terms of a fixedinterstellar extinction law. Between 1400 and 2740 A, the extinctioncurve for each star can be well represented by two parts; astraight-line scattering component and a Lorentzian 2200 A absorptionfeature. Independent variations are found in both parts and these cannotbe explained by photometric or spectral classification errors. Bothparts vary smoothly, implying that there is no fixed extinction law, andone star in three is found to depart from the mean law by more than 1mag at either 1500 or 2200 A. The two variations allow not only all 154stars to be explained but also anomalous stars reported by otherauthors. These are not special but merely situated towards the limits ofthe variations. A variation in the relative proportions of graphite andsilicate grains goes some way towards explaining the observations. Theprofile of the 2200 A feature is determined, the symmetrical shape isconfirmed, and the profile fits a Lorentzian very closely.
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Observations of interstellar diffuse absorption band at 4430 A
Observations of the interstellar diffuse absorption band at 4430 A for800 O and B stars in Neckel's (1967) catalog are being carried out, and482 spectra obtained up to September 1983 have been reduced. It isconfirmed that the strength of the interstellar diffuse absorption bandat 4430 A does not simply relate to the abundance of interstellar grainson the line of sight. The relation between the color excess E(B-V) andthe equivalent width of the band to the direction of l = 130-140 deg andb = -5 to +5 deg shows that some parameter(s) other than E(B-V) is (are)needed to understand the cause of this band.
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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.
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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.
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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.
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Wavelength dependence of interstellar polarization and ratio of total to selective extinction
A multichannel polarimeter-photometer which uses dichroic filters toseparate the (UBVR) spectral regions is described. The instrument wasused with a 24-inch rotatable tube telescope for polarimetricobservation of nearby stars. Polarization data for 364 nearby stars aretabulated, together with the wavelength dependence of linear andinterstellar polarization.
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Wavelength dependence of polarization. XXVI. The wavelength of maximum polarization as a characteristic parameter of interstellar grains.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79..581C&db_key=AST
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A search for eliptical polarization in starlight.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..576W&db_key=AST
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Rotation galactique dans une region de Cas.
Not Available
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La mesure des vitesses radiales AU prisme objectif.11 Revision et resultats nouveaux dans la SA 8.
Not Available
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Wavelength dependence of polarization. X. Interstellar polarization.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967AJ.....72..887C&db_key=AST
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Spiral arms
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967MNRAS.137..337D&db_key=AST
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Catalogue d'etoiles O et B.
Not Available
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Photoelectric 4430 A observations of 506 O, B and A stars.
Not Available
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Absorption, structure et rotation de la Galaxie dans une région de Cassiopée
Not Available
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Troisième catalogue de l'Observatoire de Besançon comprenant 764 étoiles réduites à 1950, 0 sans mouvement propre et 326 étoiles FK3 pour l'époque moyenne d'observation
Not Available
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INHABITED SKY
