|Simultaneous Optical and Near-Infrared Spectropolarimetry of Type 2 Seyfert Galaxies|
We present optical and near-infrared spectropolarimetry of the nuclei offour type 2 Seyfert galaxies, Mrk 463E, Mrk 1210, NGC 1068, and NGC4388. The data were obtained simultaneously, covering the wavelengthrange of 0.46-2.5 μm. We model the polarizations from twodust-scattering components: (1) scattering in dusty regions inionization cones and (2) scattering in a torus surrounding a type 1nucleus. The polarizations from electron scattering in the cones anddichroic absorption by aligned dust grains in the torus are alsocompared with the observations. We confirmed that a combination ofelectron and dust scattering in the ionization cones is the preferredmechanism for the optical continuum polarization. For the near-infrared,dichroic absorption by aligned grains can explain the continuumpolarization of Mrk 463E and Mrk 1210 as well as NGC 1068. Visualoptical depths of the order of 10-20 are estimated for dichroicabsorption in these nuclei. Dust scattering in the torus, whose grainsize distribution is assumed to be the same as in the Galactic diffuseinterstellar medium, cannot reproduce the observed spectral slope of thenear-infrared polarization and total nuclear flux simultaneously.However, this might only indicate that the grain size distribution inthe torus of active galactic nuclei (AGNs) is different, and dustscattering with moderate optical depth and dominated by large grainsmight provide a reasonable explanation for the near-infrared radiationfrom AGNs.
|Simultaneous Extreme Ultraviolet and Optical Observations of the Magnetic Cataclysmic Variable PQ Geminorum|
We present the results of simultaneous optical polarimetry and EUVspectroscopy and photometry of PQ Gem, a magnetic cataclysmic variablewhich shows observational properties of the strongly magnetic AM Herclass, as well as the weaker field DQ Her stars. The EUV spectrum of PQGem is weak, showing continuum blueward of 80 Angstroms and a fewpossible weak emission lines due to Mg, Si, and Ne. The EUV light curvehas a similar appearance to previous X-ray data obtained for PQ Gem,including a narrow "dip" feature that is modulated with the white dwarfspin period. Observed polarization variations on the spin period,modeled by a slightly modified version of that used in Potter et al.,matched the optical light curve and linear polarization curve reasonablywell, but not the position angle variation. The EUV properties of PQ Gemcan also be understood in the context of this model.
|ROSAT Survey Observations of the Monogem Ring|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...463..224P&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.
|Optical studies of interstellar material in low density regions of the Galaxy. I - A survey of interstellar NA I and CA II absorption toward 57 distant stars|
We present high-resolution spectra of the Na I D and Ca II K linestoward 57 late-O and early-B stars along extended (d greater than 1 kpc)low-density paths through the Milky Way disk and halo. The sight linespreferentially sample diffuse gas in the interstellar medium (ISM) alonginterarm, Galactic center, and high latitude directions. We measureequivalent widths, apparent column densities, and absorption componentstructure. The Ca II to Na I ratios presented as a function of velocityfor each sight line exhibit variations due to elemental depletion,ionization, and density enhancements. Absorption along high latitudesight lines is kinematically simpler than it is along interarm andGalactic center sight lines. Galactic rotation noticeably broadens theabsorption profiles of distant stars located in these latter directions.Along several sight lines, we see Ca II absorption at velocitiescorresponding to large distances (/z/ about 1 kpc) from the Galacticplane. The effects of differences in the Ca II and Na I scale heightsand nonzero velocity dispersions are readily apparent in the data. Briefnotes are given for several sight lines with interesting absorptionproperties.
|HD 66665: A Sharp-Lined B Star with Exceptionally Strong UV Resonance Lines|
|Non-LTE, line-blanketed model atmospheres for late O- and early B-type stars|
The use of non-LTE line-blanketed model atmospheres to analyze thespectra of hot stars is reported. The stars analyzed are members ofclusters and associations, have spectral types in the range O9-B2 andluminosity classes in the range III-IV, have slow to moderate rotation,and are photometrically constant. Sampled line opacities of iron-groupelements were incorporated in the radiative transfer solution; solarabundances were assumed. Good to excellent agreement is obtained betweenthe computed profiles and essentially all the line profiles used to fixthe model, and reliable stellar parameters are derived. The synthetic MII 5581 equivalent widths agree well with the observed ones at the lowend of the temperature range studied, but, above 25,000 K, the syntheticline is generally stronger than the observed line. The behavior of theobserved equivalent widths of N II, N III, C II and C III lines as afunction of Teff is studied. Most of the lines show much scatter, withno consistent trend that could indicate abundance differences from starto star.
|Uvby-beta observations of 528 type B stars with V between the 8th and 9th magnitude|
The paper presents uvby-beta measurements of 528 type B stars selectedfrom the SAO Catalog on the basis of two criteria: the spectral types inthe range B3-B5 and mV between the 8th and the 9th magnitude. Reddeningindependent (c1) values are estimated from the spectral classificationand compared to the observed values. No systematic trend with observed(b-y), H-beta, or spectral type appears to be present, but the range of(c1) residuals is surprisingly large. A rather large part of the starshas small beta values, smaller than for the BIa supergiants. Only twoare classified as O stars and most of them have the suffix e, ne, ornne. Most beta values for the O type stars are slightly above the upperlimit of 2.585 m.
|Broad-band photometry of selected southern ultraviolet-bright stars.|
|The distribution of interstellar AL III away from the Galactic plane|
IUE spectra are analyzed to study the density distribution ofinterstellar Al III away from the Galactic plane. In most cases, themeasured values of the relative line strengths are consistent with onlymodest levels of line saturation. Al III is found to have an exponentialscale height and 1 sigma errors of 1.02(+0.36, -0.24) kpc. For the sameset of 70 stars, the scale height and 1 sigma errors for H I are0.67(+0.21, -0.16) kpc. The Al III scale height is similar to the valueobtained for free electrons from pulsar dispersion measures. The ionizedgas traced by Al III is somewhat more extended than the neutral gastraced by H I but less extended than the very highly ionized gas tracedby Si IV, C IV, and N V.
|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.
|Highly ionized interstellar gas located in the Galactic disk and halo|
High-resolution IUE absorption line spectra have been obtained for 40distant stars in order to study the distribution of interstellar H I, SiIV, C IV, and N V in the Galactic disk and lower halo. Respectivemidplane densities of 2 x 10 to the -9th, 7 x 10 to the -9th, and 3 x 10to the -9th are found for Si IV, C IV, and Ni V. Both column density andvelocity data indicate that the highly ionized gas (HIG) is considerablymore extended in directions away from the Galactic plane than is H I orSi II. The absorption-line velocities for the halo HIG are consistentwith the notion that halo gas in the inner Galaxy rotates more slowlythan gas in the underlying disk. The derived column densities suggest anexponential scale height for the HIG of about 3 kpc; however, a simpleexponential distribution is a poor representation of the distribution ofthe gas. It is concluded that a full explanation of the origin of thehalo HIG will probably require a blending of ideas from the Galacticfountain and the photoionized halo models.
|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.
|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.
|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 survey of ultraviolet objects|
An all-sky survey of ultraviolet objects is presented together with astatistical analysis that leads to the conclusion that there is asignificantly higher population of hot subdwarfs lying below themain-sequence than hitherto thought. The distribution of all ultravioletobjects, main sequence ultraviolet objects, and MK unclassifiedultraviolet objects are shown in galactic coordinates, and the absolutemagnitudes and color-color diagrams for these groups are presented.Scale heights are derived, giving values similar to planetary nebulaefor the hottest groups.
|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.
|Optical observations of ultraviolet objects. I - Spectral classification of 103 stars /l = 200-275 deg/|
Results are presented of a program of spectral classification of 103stars originally selected as ultraviolet objects from TD-1 satellitephotometry with the S2/68 experiment. Most of the objects appear to bespectroscopically normal stars; the method of selection yielded a sampleof relatively unreddened B stars at distances up to about 2 kpc. Thisresult is compared with recent studies of the spatial distribution ofinterstellar extinction in the same regions of the sky.
|H-beta photometry of northern intermediate galactic latitude early-type stars and galactic structure away from the plane|
Photoelectric H-beta photometry is presented for 255 early-type stars atintermediate galactic latitudes. Absolute magnitudes and distances arederived for the more luminous stars. Those with visual magnitudes lessthan or equal to 2.5 and at distances of up to 1 kpc from the galacticplane may follow the spiral structure in the plane.
|On the origin of intermediate-latitude OB stars|
An attempt is made to trace the origin of early-type stars observed atappreciable distances from the galactic plane. Because uncertainties inthe proper motions make space motions and hence dynamical lifetimesrather inaccurate, a theory of oscillations normal to the plane has beenused to compute radial velocities for 138 intermediate-latitude OBstars. These theoretical values are then compared with the observedradial velocities, and it is found that the low-velocity stars wereprobably ejected from the plane some time after formation, while thehigh-velocity stars were ejected very soon after formation. Velocitiesof ejection perpendicular to the plane are computed and show a narrowdistribution with a mean absolute value of 7 km/s together with a spreadof velocities from about 40 to over 200 km/s. The data are in reasonableagreement with a 'sling' effect and 'runaway' origin for the stars inthe sample.
|Equivalent widths and rotational velocities of southern early-type stars|
|The Bibliographical Star Index|
|Some Spectroscopic Characteristics of the OB Stars: an Investigation of the Space Distribution of Certain OB Stars and the Reference Frame of the Classification|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971ApJS...23..257W&db_key=AST
|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|
|Photoelectric measures of the 4430 A diffuse interstellar band|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963MNRAS.125..141W&db_key=AST
|Distances of southern B-stars and galactic structure from Hγ-luminosities|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961MNRAS.123..191B&db_key=AST
|Three-Color Photometry of U Geminorum During an Outburst|