Contingut
Imatges
Carregar la teva Imatge
DSS Images Other Images
Articles Relacionats
Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| The Unusual 2001 Periastron Passage in the ``Clockwork'' Colliding-Wind Binary WR 140
We follow, using both optical spectroscopy and photometry, the``textbook'' colliding-wind WR+O binary WR 140 through and between theperiastron passages of 1993 and 2001. An extensive collection ofhigh-quality spectra allows us to derive precise orbital elements forboth components simultaneously. We confirm the extremely higheccentricity of the system, e=0.881+/-0.005, find an excellent match ofthe newly derived period to the previous estimates, P=2899.0+/-1.3 days,and improve the accuracy of the time of periastron passage,T0=HJD2,446,147.4+/-3.7. Around periastron, at orbital phasesφ~0.995-1.015, additional emission components appear on the tops ofthe broad Wolf-Rayet emission lines of relatively low ionizationpotential. The phase-dependent behavior of these excess line emissionspoints to their origin in the wind-wind collision zone, which allows usto place some limits on the orbital inclination of the system,i=50deg+/-15deg, and half-opening angle of the bowshock cone, θ=40deg+/-15deg. The relativelysudden appearance and disappearance of the extra emission componentsprobably signify a rapid switch from an adiabatically to a radiativelydominated regime and back again. Multiyear UBV photometry provides onemore surprise: in 2001 at φ=0.02-0.06, the system went through aseries of rapid, eclipse-like events. Assuming these events to berelated to an episode of enhanced dust formation at periastron, weestimate the characteristic size of the dust grains to be a~0.07 μm.
| Wind Inhomogeneities in Wolf-Rayet Stars. IV. Using Clumps to Probe the Wind Structure in the WC8 Star HD 192103
We present the most intensive, high-quality spectroscopic monitoring ofoptical Wolf-Rayet emission lines ever obtained. The Wolf-Rayet star HD192103 (=WR 135; subtype WC8) was observed in the 5650-5840 Åregime alternately from both the William Herschel Telescope and theCanada-France-Hawaii Telescope. The final data consist of a series of197 spectra spread over 64 hr, each with a resolving powerλ/Δλ~=20,000 and a signal-to-noise ratio in thecontinuum ~=450 per 3 pixel resolution element. We clearly andunambiguously identify stochastic, structured patterns of intrinsicvariability at the 1%-2% level of the line flux in the broad C IIIλ5696 emission line. The λ5801/12 doublet emission is alsofound to be variable at the 0.2%-0.5% level of the line flux. We find acorrelation between the variability patterns observed in C III and C IV,which suggests a significant overlap in the emission volumes of thesetransitions, although C IV is known to arise somewhat closer to thestar. We attempt to reproduce the observed line profile variationpatterns using a simple phenomenological model, which assumes the windto be fully clumped. With a minimal set of assumptions, we are able toreproduce both the shape and the variability in the C III λ5696emission profile. We show that the variability pattern providesconstraints on the radial extent of WR 135's wind where C III isproduced, as well as on the local wind acceleration rate. However, oursimple clump model does not reproduce the lower variability in the C IVdoublet unless we assume the C IV emission to occur in a much largervolume than C III, implying that significant C IV emission occursfarther out in the wind than C III. We suggest that while some C IVemission might occur farther out, possibly because of reionization fromshocks, a more likely explanation is that wind clumping significantlyincreases with distance from the star, leading to larger variabilitylevels in C III, formed farther out than most of C IV. Alternatively,optical depth effects and/or local ionization gradients within clumpscould conspire to attenuate clumping effects in the C IV emission linewhile enhancing them in the C III line.
| A 2.3 Day Periodic Variability in the Apparently Single Wolf-Rayet Star WR 134: Collapsed Companion or Rotational Modulation?
The apparently single WN 6 type star WR 134 (HD 191765) is distinguishedamong the Wolf-Rayet star population by its strong, presumably cyclical(P~2.3 day) spectral variations. A true periodicity-which is still verymuch debated-would render WR 134 a prime candidate for harboring eithera collapsed companion or a rotating, large-scale, inhomogeneous outflow.We have carried out an intensive campaign of spectroscopic andphotometric monitoring of WR 134 from 1989 to 1997 in an attempt toreveal the true nature of this object. This unprecedentedly large dataset allows us to confirm unambiguously the existence of a coherent2.25+/-0.05 day periodicity in the line-profile changes of He IIlambda4686, although the global pattern of variability is different fromone epoch to another. This period is only marginally detected in thephotometric data set. Assuming the 2.25 day periodic variability to beinduced by orbital motion of a collapsed companion, we develop a simplemodel that aims to investigate (1) the effect of this strongly ionizing,accreting companion on the Wolf-Rayet wind structure, and (2) theexpected emergent X-ray luminosity. We argue that the predicted andobserved X-ray fluxes can only be matched if the accretion on thecollapsed star is significantly inhibited. Additionally, we performedsimulations of line-profile variations caused by the orbital revolutionof a localized, strongly ionized wind cavity surrounding the X-raysource. A reasonable fit is achieved between the observed and modeledphase-dependent line profiles of He II lambda4686. However, the derivedsize of the photoionized zone substantially exceeds our expectations,given the observed low-level X-ray flux. Alternatively, we explorerotational modulation of a persistent, largely anisotropic outflow asthe origin of the observed cyclical variability. Although qualitative,this hypothesis leads to greater consistency with the observations.
| Flux Distributions for 59 Stars in Cygnus
Absolute flux distributions are given for 59 Cygnus stars in thespectral range of 320--720 nm with a step of 5 nm. Their rms errors areon the average 2--4%. The synthetic color indices calculated for theflux distributions are compared with the observed color indices in threephotometric systems.
| The X-Ray Emission of A-Type Stars
From X-ray images in the ROSAT public archives, we determine soft X-rayfluxes, or flux upper limits, for 74 A-type stars, which have beenobserved during deep integrations with the PSPC. Nine supposedly single,late A stars (0.20 < B-V < 0.35) are found to coincide with X-raysources. The X-ray luminosities we infer for these stars range fromlevels comparable to the Active Sun, at log L_x ~27.6, to much brighteremission levels similar to those observed for active late-type binarysystems, near log L_x ~30.1. Another 10 sources are identified withearly A stars (0.0 < B-V < 0.2). Five of these are confirmeddouble stars, the rest are ostensibly single. The maximum luminosity wedetect in the early A stars, log L_x = 30.1, is 3.5 orders of magnitudebrighter than the X-ray upper limits for the nondetected stars.Additional study, including radial velocity monitoring and/or opticalinterferometry, will be needed to determine whether the putativelysingle X-ray emitting stars are in fact single, or whether theiremission is produced entirely or in part by unknown or unresolved binarycompanions. The level of X-ray emission associated with chemicallynormal, single A stars thus far appears to be uncorrelated with anyobvious stellar property, including the rotation rate, which is known togreatly influence the dynamo activity and the X-ray emission levels oflower mass stars. (SECTION: Stars)
| The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Abstract 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.
| On the relative luminosities of the stars in the Wolf-Rayet binary V444 Cygni.
A new spectroscopic estimate of the luminosity ratio q=L_WR_/L_O6_ isobtained from the dilution of the absorption lines of the O6V-IIIcomponent in the WR eclipsing binary V444 Cygni (WN5+O6). We findq=0.60+/-0.06 for the range λλ4000-6000A and q=0.56+/-0.13from IUE spectra. This clearly indicates that the light of the O6dominates the combined light of V444 Cyg. This result is in strongcontradiction with the value q=3.1 derived from the light curve solutionfor V444 Cyg (model with T_eff_=40000K for the O-star component) byHamann & Schwarz (1992), but agrees with the light curve solutionsobtained previously by Cherepashchuk (1975) and Cherepashchuk et al.(1984). The discrepancy can be explained if the model of a homogeneousextended atmosphere for WR stars applied by Hamann & Schwarz for thedetermination of q from the emission lines of He I and He II is notapplicable. Clumpy structure of WR winds proposed in earlier papers(Cherepashchuk et al. 1984; Moffat et al. 1988) should be moreapplicable.
| The Wolf-Rayet binary V444 Cygni under the spectroscopic microscope. 1: Improved characteristics of the components and their interaction seen in He I
A large accumulation of high signal-to-noise, moderate-resolutionoptical spectra has led to an unprecedented analysis of the radialvelocities of emission and absorption lines in the close binary systemV444 Cyg (WN 5 + O6 III-V). Improved orbital elements and masses areKWR = 332.6 +/- 3.0 km/s, KO = 108.4 +/- 4.7 km/s,a(sin (i)) = 35.8 +/- 0.4 solar radius, e = 0.036 +/- -0.009,MWR(sin (i))3) = 8.8 +/- 0.4 solar mass,MO((sin(i))3) = 26.3 +/- 1.0 solar mass. With i =78.7 +/- 0.5 deg from previous studies, these yield a = 38.0 +/- 0.5solar radius, MWR = 9.3 +/- 0.5 solar mass, MO =27.9 +/- 1.1 solar mass. Other results include (1) the stable presenceof short-period pulsations, P approximately equals 0.36 days in the O-Cdeviations from the W-R orbital curve based on the He II 4686 and 5412radial velocities; (2) supersynchronous rotation of the O star by afactor approximately 2: ve(sin (i)) = 215 +/- 13 km/s, (3)sensitivity, especially of the He I 4471, 4922, and 5876 lines, to thepresence of a wind-wind collision region in the form of a bow shockaround the O star.
| All-sky Stromgren photometry of speckle binary stars
All-sky Stromgren photometric observations were obtained for 303 specklebinaries. Most stars were in the range of V = 5-8. These data, whencombined with ratios of intensities from the CHARA speckle photometryprogram, will allow the determination of photometric indices for theindividual components of binary stars with separations as small as 0.05arcsec. These photometric indices will complement the stellar massesfrom the speckle interferometry observations to provide a much improvedmass-luminosity relationship.
| ICCD speckle observations of binary stars. X - A further survey for duplicity among the bright stars
Speckle interferometric observations are reported for 1123 starsselected from the Yale Bright Star Catalogue (BSC) in a continuingeffort to detect new binaries among the bright stars. Thirty-twopreviously unresolved binaries have been detected, including companionsto Xi UMa and 15 S Mon. Measures of 107 previously resolved systems,many of which resulted from earlier speckle observations, are alsopresented. No evidence of duplicity within a specific (m, Delta-m, rho)window of detectability was found for 984 bright stars. Many of thesystems discovered earlier have shown significant orbital motions, andwe present preliminary orbital elements for six binaries. This efforthas resulted in the discovery of 75 new, bright binaries. We considersome aspects of the duplicity frequencies among the diverse spectral andluminosity classes represented in this sample. We anticipate that thecompletion of a speckle survey of the BSC would lead to the discovery ofat least 200 additional binary systems with angular separations mostlybelow 0.20 arcsec. Many of these will have periods of the order of onedecade and will be accessible to complementary radial velocity programsof enhanced precision.
| Early-type stars in the stellar associations Per OB1, SCO OB1, and CYG OB1 by observations with space telescope 'Glazar'
This paper presents results of observations at 1640 A carried out inSeptember 1988 with the Soviet space telescope Glazar on the regions ofstellar associations Per OB1, Sco OB1, and Cyg OB1. Thirty twophotographs were obtained, on which 94 images of stars were identifiedand measured. In stellar associations Per OB1, Sco OB1, and Cyg OB1, 42,22, and 30 hot stars brighter than 10 mag at 1640 A were detected,respectively. A comparison of Glazar measurements of stellar magnitudeswith those available from TD-1 telescope measurements and from ANSmeasurements showed reasonably good agreement.
| The Distribution of Early Type Stars in the Direction of Stellar Associations PERSEUS-OB1 SCORPIUS-OB1 and CYGNUS-OB1
Not Available
| MK classification and photometry of stars used for time and latitude observations at Mizusawa and Washington
MK spectral classifications are given for 591 stars which are used fortime and latitude observations at Mizusawa and Washington. Theclassifications in the MK system were made by slit spectrograms ofdispersion 73 A/mm at H-gamma which were taken with the 91 cm reflectorat the Okayama Astrophysical Observatory. Photometric observations in UBV were made with the 1-meter reflector at the Flagstaff Station of U.S.Naval Observatory. The spectrum of HD 139216 was found to show a strongabsorption line of H-beta. The following new Am stars were found:HD9550, 25271, 32784, 57245, 71494, and 219109. The following new Apstars were found: HD6116, 143806, 166894, 185171, and 209260. The threestars, HD80492, 116204, and 211376, were found to show the emission inCaII H and K lines.
| Spectrophotometry of stars in Cygnus
Preliminary results of the observations of 70 stars of early spectraltypes in Cygnus are presented. Spectrophotometric data have beenobtained which can be used to study the structure of the Galaxy withrelatively high reliability.
| ICCD speckle observations of binary stars. II - Measurements during 1982-1985 from the Kitt Peak 4 M telescope
This paper represents the continuation of a systematic program of binarystar speckle interferometry initiated at the 4 m telescope on Kitt Peakin late 1975. Between 1975 and 1981, the observations were obtained witha photographic speckle camera, the data from which were reduced byoptical analog methods. In mid-1982, a new speckle camera employing anintensified charge-coupled device as the detector continued the programand necessitated the development of new digital procedures for reducingand analyzing speckle data. The camera and the data-processingtechniques are described herein. This paper presents 2780 newmeasurements of 1012 binary and multiple star systems, including thefirst direct resolution of 64 systems, for the interval 1982 through1985.
| ICCD speckle observations of binary stars. I - A survey for duplicity among the bright stars
A survey of a sample of 672 stars from the Yale Bright Star Catalog(Hoffleit, 1982) has been carried out using speckle interferometry onthe 3.6-cm Canada-France-Hawaii Telescope in order to establish thebinary star frequency within the sample. This effort was motivated bythe need for a more observationally determined basis for predicting thefrequency of failure of the Hubble Space Telescope (HST) fine-guidancesensors to achieve guide-star lock due to duplicity. This survey of 426dwarfs and 246 evolved stars yielded measurements of 52 newly discoveredbinaries and 60 previously known binary systems. It is shown that thefrequency of close visual binaries in the separation range 0.04-0.25arcsec is 11 percent, or nearly 3.5 times that previously known.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| Distribution of OB stars and absorbing matter in the region around P CYG
The results of spectrophotometric observations of 277 OB stars in a 7 x7-deg region around P Cyg, obtained in 8-sec, 45-sec, and 8-minexposures on ORWO ZU-21 plates with a 4-deg 272-A/mm-dispersionobjective prism on the 40-in. Schmidt telescope at BiurakanAstrophysical Observatory on October 14-19, 1979, are presented intables and graphs and characterized. Data reported include 400-480-nmabsolute spectrophotometric gradients, color excesses, and distances. Itis found that concentrations of OB stars with associated absorbingmatter exist toward the associations Cyg OB9 (two concentrations at 800and 1800 pc), Cyg OB3 (three concentrations at 1.4, 2.5, and 3.7 kpc),OB1 (at 1.6 kpc), Cyg OB8 (at 1.5 kpc), and over the entire observedregion at a distance of about 500 pc.
| UBV Photoelectric Photometry of 259 PZT Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980PASP...92..215G&db_key=AST
| Polarization measurements of 313 nearby stars
The linear polarization of 313 low galactic latitude stars has beenmeasured. With few exceptions all program stars have a spectral typelater than B9 and are within 600 parsec of the sun. 181 stars aresituated at the southern sky and 132 at the northern sky.
| Rotational Velocities of a0 Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJS...28..101D&db_key=AST
| Star catalogs for the Washington and Richmond photographic zenith tubes.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78..642M&db_key=AST
| Four-color and Hβ photometry for the brighter AO type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....5..109C&db_key=AST
| Observations d'étoiles AP et AM
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1....1F&db_key=AST
| Catalogue d'etoiles O et B.
Not Available
| Catalogue et bibliographie des étoiles A à spectre particulier - Deuxième supplément
Not Available
| 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
| La mesure des vitesses radiales au prisme objectif. XV. 7e liste de vitesses radiales déterminées au prisme obtif à vision directe
Not Available
|
Enviar un nou article
Enllaços Relacionats
- - No s'ha trobat enllaços -
Enviar un nou enllaç
Membre dels grups següents:
|
Dades d'Observació i Astrometria
| Constel·lació: | Cygnus |
| Ascensió Recta: | 20h16m03.40s |
| Declinació: | +38°53'52.0" |
| Magnitud Aparent: | 6.27 |
| Distancia: | 125.628 parsecs |
| Moviment propi RA: | -0.8 |
| Moviment propi Dec: | -26.4 |
| B-T magnitude: | 6.283 |
| V-T magnitude: | 6.275 |
Catàlegs i designacions:
|
INHABITED SKY
