WIKISKY.ORG
 Home Getting Started To Survive in the Universe News@Sky Astro Photo The Collection Forum Blog New! FAQ Press Login

ια Lib

Contents

Images

DSS Images   Other Images

Related articles

 Infrared 3-4 μm Spectroscopic Investigations of a Large Sample of Nearby Ultraluminous Infrared GalaxiesWe present infrared L-band (3-4 μm) nuclear spectra of a large sampleof nearby ultraluminous infrared galaxies (ULIRGs). ULIRGs classifiedoptically as non-Seyfert galaxies (LINERs, H II regions, andunclassified) are our main targets. Using the 3.3 μm polycyclicaromatic hydrocarbon (PAH) emission and absorption features at 3.1 μmdue to ice-covered dust and at 3.4 μm produced by bare carbonaceousdust, we search for signatures of powerful AGNs deeply buried alongvirtually all lines of sight. The 3.3 μm PAH emission, the signaturesof starbursts, is detected in all but two non-Seyfert ULIRGs, but theestimated starburst magnitudes can account for only a small fraction ofthe infrared luminosities. Three LINER ULIRGs show spectra typical ofalmost pure buried AGNs, namely, strong absorption features with verysmall equivalent width PAH emission. Besides these three sources, 14LINER and three H II ULIRGs' nuclei show strong absorption featureswhose absolute optical depths suggest an energy source more centrallyconcentrated than the surrounding dust, such as a buried AGN. In total,17 out of 27 (63%) LINER and 3 out of 13 (23%) H II ULIRGs' nuclei showsome degree of evidence for powerful buried AGNs, suggesting thatpowerful buried AGNs may be more common in LINER ULIRGs than in H IIULIRGs. The evidence of AGNs is found in non-Seyfert ULIRGs with bothwarm and cool far-infrared colors. These spectra are compared with thoseof 15 ULIRGs' nuclei with optical Seyfert signatures taken forcomparison. The overall spectral properties suggest that the totalamount of dust around buried AGNs in non-Seyfert ULIRGs issystematically larger than that around AGNs in Seyfert 2 ULIRGs. Weargue that the optical (non)detectability of Seyfert signatures inULIRGs is highly dependent on how deeply buried the AGNs are, and thatit is essential to properly evaluate the energetic importance of buriedAGNs in non-Seyfert ULIRGs. Evolution of interacting binaries with a B type primary at birthWe revisited the analytical expression for the mass ratio distributionfor non-evolved binaries with a B type primary. Selection effectsgoverning the observations were taken into account in order to comparetheory with observations. Theory was optimized so as to fit best withthe observed q-distribution of SB1s and SB2s. The accuracy of thistheoretical mass ratio distribution function is severely hindered by theuncertainties on the observations. We present a library of evolutionarycomputations for binaries with a B type primary at birth. Some liberalcomputations including loss of mass and angular momentum during binaryevolution are added to an extensive grid of conservative calculations.Our computations are compared statistically to the observeddistributions of orbital periods and mass ratios of Algols. ConservativeRoche Lobe Over Flow (RLOF) reproduces the observed distribution oforbital periods but fails to explain the observed mass ratios in therange q in [0.4-1]. In order to obtain a better fit the binaries have tolose a significant amount of matter, without losing much angularmomentum. Observed Orbital EccentricitiesFor 391 spectroscopic and visual binaries with known orbital elementsand having B0-F0 IV or V primaries, we collected the derivedeccentricities. As has been found by others, those binaries with periodsof a few days have been circularized. However, those with periods up toabout 1000 or more days show reduced eccentricities that asymptoticallyapproach a mean value of 0.5 for the longest periods. For those binarieswith periods greater than 1000 days their distribution of eccentricitiesis flat from 0 to nearly 1, indicating that in the formation of binariesthere is no preferential eccentricity. The binaries with intermediateperiods (10-100 days) lack highly eccentric orbits. Tidal Effects in Binaries of Various PeriodsWe found in the published literature the rotational velocities for 162B0-B9.5, 152 A0-A5, and 86 A6-F0 stars, all of luminosity classes V orIV, that are in spectroscopic or visual binaries with known orbitalelements. The data show that stars in binaries with periods of less thanabout 4 days have synchronized rotational and orbital motions. Stars inbinaries with periods of more than about 500 days have the samerotational velocities as single stars. However, the primaries inbinaries with periods of between 4 and 500 days have substantiallysmaller rotational velocities than single stars, implying that they havelost one-third to two-thirds of their angular momentum, presumablybecause of tidal interactions. The angular momentum losses increase withdecreasing binary separations or periods and increase with increasingage or decreasing mass. Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type starsThis paper presents the catalogue and the method of determination ofaveraged quadratic effective magnetic fields < B_e > for 596 mainsequence and giant stars. The catalogue is based on measurements of thestellar effective (or mean longitudinal) magnetic field strengths B_e,which were compiled from the existing literature.We analysed the properties of 352 chemically peculiar A and B stars inthe catalogue, including Am, ApSi, He-weak, He-rich, HgMn, ApSrCrEu, andall ApSr type stars. We have found that the number distribution of allchemically peculiar (CP) stars vs. averaged magnetic field strength isdescribed by a decreasing exponential function. Relations of this typehold also for stars of all the analysed subclasses of chemicalpeculiarity. The exponential form of the above distribution function canbreak down below about 100 G, the latter value representingapproximately the resolution of our analysis for A type stars.Table A.1 and its references are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/631 and Tables 3 to 9are only available in electronic form at http://www.edpsciences.org Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin iThis work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897 Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statisticsThe Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521 The proper motions of fundamental stars. I. 1535 stars from the Basic FK5A direct combination of the positions given in the HIPPARCOS cataloguewith astrometric ground-based catalogues having epochs later than 1939allows us to obtain new proper motions for the 1535 stars of the BasicFK5. The results are presented as the catalogue Proper Motions ofFundamental Stars (PMFS), Part I. The median precision of the propermotions is 0.5 mas/year for mu alpha cos delta and 0.7mas/year for mu delta . The non-linear motions of thephotocentres of a few hundred astrometric binaries are separated intotheir linear and elliptic motions. Since the PMFS proper motions do notinclude the information given by the proper motions from othercatalogues (HIPPARCOS, FK5, FK6, etc.) this catalogue can be used as anindependent source of the proper motions of the fundamental stars.Catalogue (Table 3) is only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/222 Do the physical properties of Ap binaries depend on their orbital elements?We reveal sufficient evidence that the physical characteristics of Apstars are related to binarity. The Ap star peculiarity [represented bythe Δ(V1-G) value and magnetic field strength] diminishes witheccentricity, and it may also increase with orbital period(Porb). This pattern, however, does not hold for largeorbital periods. A striking gap that occurs in the orbital perioddistribution of Ap binaries at 160-600d might well mark a discontinuityin the above-mentioned behaviour. There is also an interestingindication that the Ap star eccentricities are relatively lower thanthose of corresponding B9-A2 normal binaries for Porb>10d.All this gives serious support to the pioneering idea of Abt &Snowden concerning a possible interplay between the magnetism of Apstars and their binarity. Nevertheless, we argue instead in favour ofanother mechanism, namely that it is binarity that affects magnetism andnot the opposite, and suggest the presence of a newmagnetohydrodynamical mechanism induced by the stellar companion andstretching to surprisingly large Porb. Binary Star Orbits from Speckle Interferometry. I. Improved Orbital Elements of 22 Visual SystemsImproved orbital elements for 22 binary systems are presented. For 12systems, masses are calculated using available trigonometric parallaxesand making certain assumptions regarding the mass ratio. For the other10 systems, provisional elements are provided that should providerelatively accurate ephemerides for the next decade. Inclination of the Orbital Planes of Visual BinariesThe inclination of the orbital planes of 78 visual binaries with knownorbits with respect to the galactic was examined. No double stargroupings were found having approximately equal orientation of theirorbital planes. Viewed the orbital plane north poles there are morebinary systems with counterclockwise motion than those moving clockwise. New orbits.Not Available On the HIPPARCOS photometry of chemically peculiar B, A, and F starsThe Hipparcos photometry of the Chemically Peculiar main sequence B, A,and F stars is examined for variability. Some non-magnetic CP stars,Mercury-Manganese and metallic-line stars, which according to canonicalwisdom should not be variable, may be variable and are identified forfurther study. Some potentially important magnetic CP stars are noted.Tables 1, 2, and 3 are available only in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html The HR-diagram from HIPPARCOS data. Absolute magnitudes and kinematics of BP - AP starsThe HR-diagram of about 1000 Bp - Ap stars in the solar neighbourhoodhas been constructed using astrometric data from Hipparcos satellite aswell as photometric and radial velocity data. The LM method\cite{luri95,luri96} allows the use of proper motion and radial velocitydata in addition to the trigonometric parallaxes to obtain luminositycalibrations and improved distances estimates. Six types of Bp - Apstars have been examined: He-rich, He-weak, HgMn, Si, Si+ and SrCrEu.Most Bp - Ap stars lie on the main sequence occupying the whole width ofit (about 2 mag), just like normal stars in the same range of spectraltypes. Their kinematic behaviour is typical of thin disk stars youngerthan about 1 Gyr. A few stars found to be high above the galactic planeor to have a high velocity are briefly discussed. Based on data from theESA Hipparcos astrometry satellite and photometric data collected in theGeneva system at ESO, La Silla (Chile) and at Jungfraujoch andGornergrat Observatories (Switzerland). Tables 3 and 4 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html Mass determination of astrometric binaries with Hipparcos. II. Selection of candidates and resultsIn a previous paper (\cite{Mar97}) we have shown that for double starswith orbital periods smaller than about 25 years, it was possible todetermine from the Hipparcos data, the mass ratio B of the components orthe difference between the mass and intensity ratios, beta -B, providedthe orbital elements of the relative orbit are available. From anextensive literature search we have selected 145 potential systems, ofwhich 46 yielded eventually a satisfactory solution. For eight systemswith the largest separations, the peculiarities of the natural directionassociated to the Hipparcos observations, the 'hippacentre', have beenfully exploited to derive the mass ratio of the components without anyadditional assumption. For the remaining 38, the derivation of the massratio was possible only by taking the magnitude difference between thetwo components from other sources. The parallax determinedsimultaneously, is then used to produce the individual masses of thecomponents. The astrophysical relevance of the results is discussed andwhen possible (17 systems) the masses are compared to ground-basedvalues. The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circleThe 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. ICCD Speckle Observations of Binary Stars. XVI. Measurements During 1982-1989 from the Perkins 1.8-M Telescope.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.1623F&db_key=AST MSC - a catalogue of physical multiple starsThe MSC catalogue contains data on 612 physical multiple stars ofmultiplicity 3 to 7 which are hierarchical with few exceptions. Orbitalperiods, angular separations and mass ratios are estimated for eachsub-system. Orbital elements are given when available. The catalogue canbe accessed through CDS (Strasbourg). Half of the systems are within 100pc from the Sun. The comparison of the periods of close and widesub-systems reveals that there is no preferred period ratio and allpossible combinations of periods are found. The distribution of thelogarithms of short periods is bimodal, probably due to observationalselection. In 82\% of triple stars the close sub-system is related tothe primary of a wide pair. However, the analysis of mass ratiodistribution gives some support to the idea that component masses areindependently selected from the Salpeter mass function. Orbits of wideand close sub-systems are not always coplanar, although thecorresponding orbital angular momentum vectors do show a weak tendencyof alignment. Some observational programs based on the MSC aresuggested. Tables 2 and 3 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 ICCD Speckle Observations of Binary Stars.XV.An Investigation of Lunar Occultation SystemsAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2260M&db_key=AST ICCD Speckle Observations of Binary Stars. XIII. Measurements During 1989- 1994 From the Cerro Tololo 4 M TelescopeAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111..936H&db_key=AST The λ 3984 feature in late-B spectroscopic binaries.We report about a spectroscopic study aimed at searching the line Hg IIλ 3984 in a sample of 28 spectroscopic binaries with primaries inthe same temperature range as HgMn stars. One system, HD 75642, showsthis line very prominently. In another system, HD 41040, Hg may besomewhat overabundant, while HD 87751 shows marginal Mn and Penhancement. The present study does not bring a definitive answer to thequestion of the relation between binarity, slow rotation, and theappearance of HgMn anomalies in late B stars, possibly because othereffects (like the influence of a magnetic field), which could not betaken into consideration, are important too. In the course of thisstudy, 11 new double-lined spectroscopic binaries were discovered, 10 ofwhich were previously known as single-lined systems. Of particularinterest among them are 4 stars that may have the Si or He weakpeculiarities. Speckle observations of visual and spectroscopic binaries. VI.Not Available Speckles and Shadow BandsSpeckle interferometry has for the past two decades provided a means tomeasure very accurate relative positions of binary stars, data crucialto the fundamental determination of basic stellar parameters. As atechnique for observing small angular separations speckle interferometryis exceeded only by long baseline interferometry (a technique still ininfancy) and the observation of lunar occultation phenomena. As the moonpasses in front of stars the light coming from those stars is occulted.Occultations of binary stars can determine relative intensities and canmeasure separations which are comparable to those measured bylong-baseline interferometers. The data are difficult to interpret sincethe measured separation is a projection of the true angular separationand non-standard filters are often used. No complete listing of alloccultation measures has been published since the compilation of DavidEvans (IAU Colloquium No. 62, Current Techniques in Double and MultipleStar Research, Lowell Observatory Bulletin No. 167, 1981, eds.Harrington, R.A. \& Franz, O.G., Lowell Observatory, Flagstaff). Thedissertation presents 772 measures of 357 systems, an increase of 60\%over the Evans catalog. The methodology of speckle interferometry ispresented, followed by 362 re-reduction measures and 253 new measures.The re-reduction measures were cases where prior analysis showed nocompanion. With improved reduction algorithms, detection frequencysignificantly increased. One observation in eight previously showing nocompanion produced a measurable result. Results were obtained with the1.8-m Perkins telescope of Lowell Observatory, the 2.5-m Hookertelescope of Mt. Wilson Observatory, the 3.8-m Mayall telescope of KittPeak National Observatory and the 4.0-m telescope at Cerro TololoInterAmerican Observatory. All but 130 of the occultation objects havespeckle observations. The likelihood of future detection by speckle isconsidered. An analysis of 131 negative results is presented. Of theremaining 96 systems, 66 have been detected by speckle interferometry,13 for the first time, and 17 new orbits have been calculated. Of theseorbits, five (HR 793 = Bla Aa, ADS 3608 = A 1844, HR 3880 = McA 34, HR5652 = B 2531 Aa, HR 7776 = $\beta$ Cap) have improved elements overprevious orbit calculations, four (BD$+$24~1805 = Cou 929, ADS 17052 = A2700, HR 9041 = Fin 359, ADS 17111 = A 2100) have previous butsignificantly different orbits, five (HR 132 = McA 1 Aa, HR 1808 = McA19 Aa, HR 2343 = Btz Aa, HR 8060 = Fin 328, HR 8704 = McA 73) are firstorbits, and three (HR 763 = McA 7, HR 2130 = McA 24, HR 2846 = McA 30Aa) are first orbits of spectroscopic binaries. The occultation catalog,speckle measures, and new orbits will be presented in subsequent CHARApublications. The detection of occultation binaries by speckleinterferometry seems to be predictable, however, there appear to be asmall sample of occultation binaries which cannot be detected. These maybe spurious. Lunar occultation measures place a good limit on $\Delta$mfor speckle of about 3.0. CHARA hopes to complete a survey of alloccultation objects with current scheduled runs which should result in afurther five to ten objects resolved for the first time. While the rateof occultation measures has dropped significantly, they are stillcontinuing to provide useful complementary data for other binary starmethods. (SECTION: Dissertation Summaries) The Relation between Rotational Velocities and Spectral Peculiarities among A-Type StarsAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&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. Radio continuum emission from stars: a catalogue update.An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed. A new list of effective temperatures of chemically peculiar stars. II.Not Available Second astrolabe catalogue of Santiago.Positions for 350 FK5 and 164 FK5 Extension stars as determined with theDanjon astrolabe of Santiago and differences astrolabe-catalogue aregiven for Equinox J2000.0 and for the mean observation epoch of eachstar. The average mean error in alpha is +/-0.005s and +/-0.07" indelta. The mean epoch of observation of the catalogue is J1979.96. ICCD speckle observations of binary stars. VIII - Measurements during 1989-1991 from the Cerro Tololo 4 M telescopeOne-thousand eighty-eight observations of 947 binary star systems,observed by means of speckle interferometry with the 4 m telescope onCerro Tololo, are presented. These measurements, made during the period1989-1991, comprise the second installment of results stemming from theexpansion of our speckle program to the southern hemisphere.
Submit a new article

• - No Links Found -