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BV RI observations of the radio source S5 0716+71
Photometric observations of the radio source S5 0716+714 were obtainedin BV RI filters from January 20, 1998 to January 9, 2001 with Zeiss-600and Zeiss-1000 telescopes of the Special Astrophysical Observatory ofthe Russian Academy of Sciences. The light curves in all the bands aresynchronous, providing evidence for the real variability of the objectin timescales, from hundreds of days to 5 10 min. No time shift betweenevents in the adjacent filters was detected. The variability spectrum atfrequencies of 0.003 100 d-1 (3.5 × 10-8 1.1 × 10-3 Hz) isclose to that of a flicker noise. The optical spectral index α (S v α) varies from -1.59 at the minimum to -1.13 at themaximum brightness. Measurements of linear polarization in BV R carriedout on April 12 13, 2000 confirmed a high degree of polarization andrapid fluctuations of the polarization in a timescale of 15 30 min,whose amplitude decreases at red wavelengths. All the optical propertiesof the source, its compactness, the absence of spectral lines, the highdegree of polarization, and very rapid fluctuations of the brightness,polarization, and spectral index, suggest a synchrotron origin foroptical radiation. It may be that we are observing the radiation from agroup of very compact bodies (10-10 arcsec) at various stages oftheir evolution.
| New optical polarization measurements of quasi-stellar objects. The data
New linear polarization measurements (mainly in the V band) arepresented for 203 quasi-stellar objects (QSOs). The sample is made up of94 QSOs located in the North Galactic Pole (NGP) region and of 109 QSOsin the South Galactic Pole (SGP) region. First time measurements havebeen obtained for 184 QSOs. Among them, 109 known radio-emitters, 42known Broad Absorption Line (BAL) QSOs, and 1 gravitationally lensedquasi-stellar object. We found high polarization levels (p > 3%) for12 QSOs, including the BAL QSO SDSS J1409+0048. For10 objects, measurements obtained at different epochs do exist. Two ofthem show evidence for variability: the highly polarized BL Laccandidate PKS 1216-010 and the radio sourcePKS 1222+037.Based on observations collected at the European Southern Observatory(ESO, La Silla and Paranal). Table 4 is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/757
| High-resolution imaging polarimetry of HL Tau and magnetic field structure
We present high-quality near-infrared imaging polarimetry of HL Tau at0.4-0.6 arcsec resolution, obtained with Subaru/CIAO and UKIRT/IRCAM.Three-dimensional Monte Carlo modelling with aligned oblate grains isused to probe the structure of the circumstellar envelope and themagnetic field, as well as the dust properties. At the J band, thesource shows a centrosymmetric pattern dominated by scattered light. Inthe H and K bands, the central source becomes visible and itspolarization appears to be dominated by dichroic extinction, with aposition angle inclined by ~40° to the disc axis. The polarizationpattern of the environs on scales up to 200 au is consistent with thesame dichroic extinction signature superimposed on the centrosymmetricscattering pattern. These data can be modelled with a magnetic fieldwhich is twisted on scales from tens to hundreds of au, or alternativelyby a field which is globally misaligned with the disc axis. A uniquesolution to the field structure will require spatially resolved circularpolarization data. The best-fitting Monte Carlo model indicates ashallow near-infrared extinction law. When combined with the observedhigh polarization and non-negligible albedo, these constraints can befitted with a grain model involving dirty water ice mantles in which thelargest particles have radii slightly in excess of 1 μm. Thebest-fitting model has an envelope structure which is slightly flattenedon scales up to several hundred au. Both lobes of the bipolar outflowcavity contain a substantial optical depth of dust (not just within thecavity walls). Curved, approximately parabolic, cavity walls fit thedata better than a conical cavity. The small inner accretion discobserved at millimetre wavelengths is not seen at this spatialresolution.
| 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?
| Investigating the nature of the z =~ 2.8 submillimeter selected galaxy SMM J02399-0136 with VLT spectropolarimetry
We present deep optical spectropolarimetry of SMM J02399-0136 (z=2.8)done with the VLT Antu 8.2 m telescope equipped with FORS1. Moderatecontinuum and emission line polarization are measured (P ~ 5%). We donot detect broad lines in scattered flux as would be expected for atype-2 object but rather a polarization behaviour similar to BALquasars. This classification is confirmed by the detection of both highand low ionization broad absorption troughs and a very red continuum. Weargue that this object shares several properties with local ULIGs suchas Mrk 231 and other ultraluminous infrared Lo-BAL quasars. However, thefact that the ultraviolet spectrum is dominated by non-stellar radiationdoes not prove that the dust that is thermally radiating in the farinfrared is predominantly heated by the AGN. Since the energy that weget in the far-infrared is precisely that which is removed from theultraviolet spectrum, this could mean that the starburst is moredust-enshrouded than the AGN due to a peculiar dust distribution. Thelimits we place on the putative starburst contribution to the restframeultraviolet continuum together with constraints on the amount ofextinction provide an upper limit to the star formation rate of about2000 Msun yr-1, consistent with previously claimedhigh star formation rates level in this object. Based on observationscollected at the European Southern Observatory, Paranal, Chile (ESOProgramme 64.P-0072).
| Rapid Polarization Variability in the BL Lacertae Object S5 0716+714
We present optical polarimetry of the violently variable BL Lacertaeobject S5 0716+714, obtained over a three year period using the 6 mtelescope at the Special Astrophysical Observatory in Russia. The degreeof polarization is high and variable throughout the observations. With aminimum time resolution of 1 minute, significant variations on atimescale of 10-15 minutes are observed. The variations are complex andnot fully sampled by this data, but they are characterized by largeamplitude changes on a timescale of about 1 day superposed on smoothvariations with a timescale of about 1 week. Possible periods of 12.5,2.5, and 0.14 days have been discovered. S5 0716+714 is a highly compactradio source with nonthermal emission observed across theelectromagnetic spectrum out to gamma rays. The optical polarizationvariations are consistent with relativistically beamed synchrotronemission viewed at a very small angle to the line of sight.
| Polarization of Broad Absorption Line QSOS. I. A Spectropolarimetric Atlas
We present a spectropolarimetric survey of 36 broad absorption linequasi-stellar objects (BAL QSOs). The continuum, absorption trough, andemission-line polarization of BAL QSOs yield clues about theirstructure. We confirm that BAL QSOs are in general more highly polarizedthan non-BAL QSOs, consistent with a more equatorial viewing directionfor the former than the latter. We have identified two new highlypolarized QSOs in our sample (1232+1325 and 1333+2840). The polarizationrises weakly to the blue in most objects, perhaps owing to scatteringand absorption by dust particles. We find that a polarization increasein the BAL troughs is a general property of polarized BAL QSOs,indicating an excess of scattered light relative to direct light, andconsistent with the unification of BAL QSOs and non-BAL QSOs. We havealso discovered evidence of resonantly scattered photons in the red wingof the C IV broad emission lines of a few objects. In most cases, thebroad emission lines have lower polarization and a different positionangle than the continuum. The polarization characteristics oflow-ionization BAL QSOs are similar to those of high-ionization BALQSOs, suggesting a similar BAL wind geometry.
| Stars with ISM Polarization Observed with HPOL
Polarization data are given for stars whose polarizations are mostlyinterstellar which were observed for various programs with theUniversity of Wisconsin spectropolarimeter (HPOL) during 1989-1994.
| 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.
| Keck Spectropolarimetry of the Radio Galaxy 3C 234
We present high signal-to-noise ratio spectropolarimetric data of 3C 234observed with the 10 m Keck telescope. The data were obtained with thepolarimeter on the Low Resolution Imaging Spectrometer, covering awavelength range of 3900-9000A at moderate resolution. They show thatbroad Hα and Hβ are apparently polarized higher than theadjacent continuum but at the same position angle perpendicular to theradio axis, similar to the behavior of many Seyfert 2 galaxies reportedby Tran. As proposed for the Seyfert 2 galaxies, we interpret thecurrent data in terms of the presence of a second extended continuum,and derive a high 25% intrinsic polarization for the hidden continuumand broad emission lines, due to scattering. We are able to decomposethe observed spectrum of 3C 234 into at least three componentscomprising: (a) a scattered (polarized) continuum plus broad emissionlines from the obscured active galactic nucleus, (b) an extended,unpolarized continuum plus narrow emission lines resembling a typicalnarrow-line radio galaxy spectrum, and c) a stellar component from theunderlying host galaxy. A combination of high extinction experienced bythe scattered radiation and dilution by the unreddened extendedcontinuum, which makes up nearly half of the starlight-corrected totalflux, causes the slight increase to the red of the polarization aftercorrection for starlight dilution has been applied. Our data show that,free of the obscuring material or from another direction, 3C 234 wouldbe a luminous quasar, thus providing support for the unification ofquasars and radio galaxies. These and other observations suggest thatspatially extended continuum in AGNs may be quite common and thus shouldbe taken into account when their intrinsic nuclear continua are studied.
| 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.
| Tracing the Roots of Interstellar Mid Infrared Emission
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...275..549J&db_key=AST
| Environment Dependence of Interstellar Extinction Curves
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...274..439J&db_key=AST
| Infrared dust and millimeter-wave carbon monoxide emission in the Orion region
The far-infrared dust emission seen by the IRAS satellite in the Orionregion is analyzed as a function of the local radiation field intensity,and the dust temperature and opacity are compared with (C-12)O and(C-13)O emission. The infrared radiation is interpreted within theframework of a single-component large grain model and a multicomponentgrain model consisting of subpopulations of grains with size-dependenttemperatures. A strong dependence of the 100-micron optical depthderived is found using the large grain model on the averageline-of-sight dust temperature and radiation field. In the hotenvironment surrounding high-luminosity sources and H II regions, alldust along the line-of-sight radiates at 100 microns, and thedust-to-gas ratio, based on the 100-micron opacity and I(/C-13/O),appears to be in agreement with the standard value, about 1 percent bymass. A relationship is found between the inferred dust-to-gas ratio andthe radiation field intensity responsible for heating the dust which canbe used to estimate the gas column density from the dust opacity derivedfrom the 60- and 100-micron IRAS fluxes.
| An atlas of Hubble Space Telescope photometric, spectrophotometric, and polarimetric calibration objects
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990AJ.....99.1243T&db_key=AST
| An analysis of the shapes of ultraviolet extinction curves. II - The far-UV extinction
In this paper the properties of interstellar extinction in thefar-ultraviolet region are examined utilizing IUE extinction curves fora primary data sample of 45 reddened Milky Way OB stars. These resultsare combined with those derived for the 2175 A bump in a previous study.It is found that IUE extinction curves can be represented by linearcombinations of a Lorentzian-like 2175 A bump profile, a well-determinedFUV curvature term, and an underlying linear component. The parametersof the linear component are strongly correlated and therefore only fivefree parameters are required to fit all of the curves in our sample.Three parameters describe the 2175 A bump, one parameter describes thelinear background, and one parameter describes the strength of the FUVcurvature term. The shape of the FUV curvature is found to be identical,to within the observational errors, for all the curves in the sample -which spans virtually the entire range of extinction curve morphologiesobserved in the Milky Way.
| 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.
| An analysis on the shapes of ultraviolet extinction curves. I - The 2175 A bump
IUE data are used to investigate the properties of the 2175 Ainterstellar extinction bump toward 45 reddened Milky Way stars. Usinganalytic fitting functions, parameters are derived which describe thecentral position, FWHM, and strength of the bump. The bump position isvery stable, with an extreme deviation which is still significantlylarger than the measurement uncertainty, indicating true variability.The bump FWHM has a large range of intrinsic values, 0.77/micron to1.25/micron. The normalized bump strength varies by more than a factorof three. There are no convincing correlations among the three bumpparameters, but the width of the bump is strongly correlated with thedust grain environments. Dense quiescent regions yield broad bumps,while diffuse interstellar medium and regions of recent star formationyield narrower bumps. The absence of any correlation between bump widthand central position argues strongly against graphite grains in the sizerange prescribed by the Mathis, Rumpl, and Nordsieck (1977) model ascarriers of the bump.
| Peculiar ultraviolet interstellar extinction
In connection with investigations of the physical characteristics ofinterstellar dust, a study of objects with peculiar extinction mightprovide new insights about the composition, size distribution,formation, and destruction of the particulate matter. Meyer and Savage(1981) have found that the dust toward many stars exhibits peculiar UVextinction. The present investigation is concerned with InternationalUltraviolet Explorer (IUE) spectrophotometric measurements for a sampleof stars judged by Meyer and Savage to have highly anomalous UVextinction as inferred from the broad-band Astronomical NetherlandsSatellite (ANS) data. The reported IUE measurements provide theopportunity to determine if the ANS photometry measurements of Meyer andSavage are anomalous because of peculiar extinction.
| IUE observations of lines of sight with peculiar ultraviolet extinction
Low resolution IUE data were used to derive UV extinction curves for agroup of stars known to have peculiar extinction parameters from ANSdata. The resulting curves have a wide range of appearances. Althoughthe ratio E(BUMP)/E(B-V) differs by a factor of three in the extremecases, the wavelength of maximum absorption does not appear to change.No evidence for new fine structure in UV extinction was found. Thestructure near 62 micrometers in the existing mean extinction curvesappears to be the result of luminosity mismatch errors. The newextinction curves have shapes that separate into two distinct classes;those associated with clear field extinction and those associated withextinction in dense nebular environments. The range of variation in thecurves is so large, the common practice of ironing out the bump canproduce enormous errors in the resultant UV energy distributions whenE(B-V) 0.3.
| Ultraviolet interstellar extinction toward 1367 stars observed by ANS
Five-band UV photometry is used to investigate the character ofinterstellar extinction toward 1367 stars of spectral type B3 andearlier, with observations producing a galactic average of 5.11, 4.78,6.52, 4.10 and 1.95 at 1550, 1800, 2200, 2500, and 3300 A, respectively.Differences in the strengths of the UV extinction features of thesestars appear to be independent, since objects with either strong or weak2200 A extinction can have strong, normal or weak far-UV extinction.Further investigation reveals that some of the deviant stars areembedded in localized regions whose average extinction curves divergedramatically from the galactic mean. The anomalous extinction of theseregions attests to localized inhomogeneities in the UV characteristicsof interstellar dust. Because the evaluation of UV extinction toward aparticular star would be more accurate if based on the average curve ofthe region immediately surrounding that star rather than that of theentire Galaxy, it is recommended that the galactic average presented beused with caution to correct astronomical data of individual objects.
| The stellar distribution in the galactic anticenter.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967AJ.....72.1199M&db_key=AST
| Catalogue d'etoiles O et B.
Not Available
| Interstellar Polarization of 405 Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954ApJ...120..454H&db_key=AST
| Studies of Faint B-Type Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1950ApJ...111..495P&db_key=AST
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