A Model for the Chromosphere/Wind of 31 Cygni and Its Implications for Single Stars
I develop a detailed empirical model for the chromosphere and wind of 31Cyg based on a previously published analysis of InternationalUltraviolet Explorer spectra from the 1993 eclipse and on thethermodynamics of how the wind must be driven. I then use this model tointerpret observations of single supergiant stars and to assess theevidence that their winds are fundamentally different from those ofsupergiants in binary systems. This model naturally predicts a certainlevel of clumping of the gas to balance the pressure that drives thewind. It also predicts that anisotropic turbulence, such as would resultfrom transverse displacements of Alfven waves directed along radialmagnetic flux lines, would not give the roughly Gaussian profiles ofemission lines seen in cool giant stars. Furthermore, it implies that CII] may not tell us much at all about general conditions inchromospheres. Finally, I speculate that chaotic magnetic fields, indynamical equilibrium with the gas of the wind, are the actual drivingmechanism.
|
Properties of the ? Aur-Type Binary System 22 Vul = QS Vul
The 22 Vul system is important for studying the winds and chromospheresof cool evolved stars because the G4 I component is rotating rapidly andprobably faster than synchronously. We discuss the system's physicalproperties in the context of a wide range of constraints on them andpropose values that may be marginally better than previous ones (see theend of § 3). We use H? spectroscopy to assess the variabilityof the cool star's wind, and archival IUE observations to measurevariation of density in the wind and rotation of the chromosphere. Weargue that the terminal velocity of the wind must be at least as greatas the edge velocity of Mg II and derive a new value ofv?>~208+/-5 km s-1. Directly measuredcolumn densities for hydrogen (from Ly?), combined with columndensities for metals, imply a ?~2.5 velocity law for the wind witha mass-loss rate of ~1.6×10-8 Msolaryr-1, about 4 times the surface flux of 31 Cyg. Excitationtemperatures and turbulent velocities in the inner 3R* of thewind are similar to those in other ? Aur binaries. The apparentfaster-than-synchronous rotation Griffin and coworkers found in theoptical persists in IUE spectra out to at least 2.5R(G4 I). This impliesthat the wind is locked to the star through magnetic fields or that thematerial in the wind is viscous enough to maintain approximatelysolid-body rotation.
|
Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
|
A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
|
Astrometric orbits of SB^9 stars
Hipparcos Intermediate Astrometric Data (IAD) have been used to deriveastrometric orbital elements for spectroscopic binaries from the newlyreleased Ninth Catalogue of Spectroscopic Binary Orbits(SB^9). This endeavour is justified by the fact that (i) theastrometric orbital motion is often difficult to detect without theprior knowledge of the spectroscopic orbital elements, and (ii) suchknowledge was not available at the time of the construction of theHipparcos Catalogue for the spectroscopic binaries which were recentlyadded to the SB^9 catalogue. Among the 1374 binaries fromSB^9 which have an HIP entry (excluding binaries with visualcompanions, or DMSA/C in the Double and Multiple Stars Annex), 282 havedetectable orbital astrometric motion (at the 5% significance level).Among those, only 70 have astrometric orbital elements that are reliablydetermined (according to specific statistical tests), and for the firsttime for 20 systems. This represents a 8.5% increase of the number ofastrometric systems with known orbital elements (The Double and MultipleSystems Annex contains 235 of those DMSA/O systems). The detection ofthe astrometric orbital motion when the Hipparcos IAD are supplementedby the spectroscopic orbital elements is close to 100% for binaries withonly one visible component, provided that the period is in the 50-1000 drange and the parallax is >5 mas. This result is an interestingtestbed to guide the choice of algorithms and statistical tests to beused in the search for astrometric binaries during the forthcoming ESAGaia mission. Finally, orbital inclinations provided by the presentanalysis have been used to derive several astrophysical quantities. Forinstance, 29 among the 70 systems with reliable astrometric orbitalelements involve main sequence stars for which the companion mass couldbe derived. Some interesting conclusions may be drawn from this new setof stellar masses, like the enigmatic nature of the companion to theHyades F dwarf HIP 20935. This system has a mass ratio of 0.98 but thecompanion remains elusive.
|
VLA Observations of ζ Aurigae: Confirmation of the Slow Acceleration Wind Density Structure
Studies of the winds from single K and early M evolved stars indicatethat these flows typically reach a significant fraction of theirterminal velocity within the first couple of stellar radii. The mostdetailed spatially resolved information of the extended atmospheres ofthese spectral types comes from the ζ Aur eclipsing binaries.However, the wind acceleration inferred for the evolved primaries inthese systems appears significantly slower than for stars of similarspectral type. Since there are no successful theories for mass loss fromK and early M evolved stars, it is important to place strong empiricalconstraints on potential models and determine whether this difference inacceleration is real or an artifact of the analyses. We have undertakena radio continuum monitoring study of ζ Aurigae (K4 Ib + B5 V)using the Very Large Array to test the wind density model of Baade etal. that is based on Hubble Space Telescope (HST) Goddard HighResolution Spectrograph ultraviolet spectra. ζ Aur was monitored atcentimeter wavelengths over a complete orbital cycle, and fluxvariations during the orbit are found to be of similar magnitude tovariations at similar orbital phases in the adjacent orbit. Duringeclipse, the flux does not decrease, showing that the radio emissionoriginates from a volume substantially larger thanR3K~(150Rsolar)3 surroundingthe B star. Using the one-dimensional density model of the K4 Ibprimary's wind derived from HST spectral line profile modeling andelectron temperature estimates from previous optical and new HSTstudies, we find that the predicted radio fluxes are consistent withthose observed. Three-dimensional hydrodynamic simulations indicate thatthe accretion flow perturbations near the B star do not contributesignificantly to the total radio flux from the system, consistent withthe radio eclipse observations. Our radio observations confirm the slowwind acceleration for the evolved K4 Ib component. ζ Aur's velocitystructure does not appear to be typical of single stars with similarspectral types. This highlights the need for more comprehensivemultiwavelength studies for both single stars, which have been sadlyneglected, and other ζ Aur systems to determine if its windproperties are typical.
|
SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
|
A wind accretion wake in RW Hydrae?
RW Hydrae is an eclipsing detached binary star system, consisting of amass losing M-giant and a hot white dwarf on circular orbits. We analyzeUV observations of RW Hydrae. Approximately at phi = 0.78, clearlyunrelated to the primary eclipse, we detect in the UV light curve anevent with significantly reduced UV flux. The spectral characteristicsof this event indicate Rayleigh scattering due to a high column densityof neutral hydrogen in the line of sight to the hot white dwarf. Wemodel this observation in the framework of an accretion wake trailingthe white dwarf. This interpretation is analogous to comparable modelsfor zeta Aur systems and X-ray binaries. We find qualitative agreementbetween our 3D hydrodynamical accretion simulation and the observed UVlight curve of RW Hya. Based on observations with the InternationalUltraviolet Explorer and observations with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc. under NASA contract No. NAS5-26555.
|
The polarimetric variability of 32 CYG during its 1993 October eclipse
Six spectropolarimetric observations of 32 Cyg were taken during its1993 October eclipse. Two additional observations were made out ofeclipse. They are the first reliable high-quality polarimetricobservations of the system. The data were initially modelled assuming aspherical scattering region around the K giant only and then with anadditional accretion disc around the B star. While both models poorlyrepresented the data, it is evident that a scattering region in additionto the known extended atmosphere of the K giant is required in order toexplain the observations. It is suggested that the system is in a stateof mass transfer.
|
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.
|
The light-curve of the zeta-Aurigae-type eclipsing binary AL Velorum
Not Available
|
The 1992/93 eclipse of 31 Cygni
Extensive new ultraviolet and optical spectra of an atmospheric eclipsedefine the physical properties throughout the wind and chromosphere of31 Cyg. These data require mass loss of approximately 3 x10-8 solar masses/yr in a wind that may merge smoothly intothe chromosphere. Considerations of how energy is injected into thewind, however, suggest that the chromosphere and wind are separatestructures. Most, if not all, of the velocity structure in metalliclines, which we have heretofore simulated with Doppler widths in therange 15-25 km/s, results from differential expansion of the atmosphere.Electron densities in the inner Rstar of the chromosphere arein the range 1.5 x 109 - 2 x 108/cu cm, whichimplies clumping of the gas. The ionization of oxygen and nitrogen isconsistent with clumping by factors of 3-30 in the outer chromosphere,roughly the amount required to give enough gas pressure to support thechromosphere. Chromospheric gas in 31 Cyg becomes hotter with increasingheight, thus with decreasing optical depth, in a way that seems similarfor all the zeta Aur binaries. Excitation temperature for Fe II in1992/93 rises from about 5000 K at the deepest points sampled to about12,500 K high in the wind. Strengths of violet Balmer lines give anexcitation temperature for hydrogen of 6200-6500 K above a radial masscolumn density of approximately 0.01 g/sq cm. This amount of excitationimplies that Lyman-alpha is thermalized beneath about 4 x10-3 g/sq cm. The outer atmosphere was symmetrical to withina factor of 2 in 1992/93, although it was clearly variable at thislevel, and it had similar mass column densities as in 1982. Onemanifestation of the variability was a flow toward the B star at phases0.013-0.022 spanning velocities 45-100 km/s. Several lines of evidencepoint to a complicated and variable ionization in the wind: At largedistance from the K star, measured mass column densities are less by upto a factor of 3 than required by a smoothly flowing wind. Also, much ofthe gas beyond r = 350 solar radii = 1.75 Rstar has anegative radial velocity. Radial velocities of the shell lines imply theouter atmosphere rotates in the direction of orbital motion, possiblythrough the deflection of wind flow lines in this direction.
|
A deep atmospheric eclipse of AL Velorum
I have obtained new International Ultraviolet Explorer (IUE)observations in 1992 to search for an accretion column in and to analyzean atmospheric eclipse of AL Vel, a low luminosity zeta Aurigae binary.Rich shell spectra recorded at three phases of atmospheric eclipse givecolumn densities and excitation temperatures for the chromospheric gas.The chromospheric density falls off exponentially with a scale height of3 solar radius, an order of magnitude greater than expected for supportby thermal motions. Excitation temperatures at 2 - 5 scale heights intothe chromosphere are approximately 7000 K, with Doppler widths near 17km/s. Absorption features that could be formed in an accretion columnwere detected at phases 0.70 and 0.75 in a series of spectra spanningthe range 0.63-0.80 in orbital phase. They imply a very slowacceleration of the wind, consistent with results for other zeta Aurbinaries, but the wind speed implied is inconsistent with profiles ofwind lines. The terminal velocity of this wind, greater than orapproximately = 360 km/s, is higher than that in any of the other zetaAur binaries. Wind and chromospheric features in 1992 were much moreprominent than in 1988, which implies that both the wind andchromosphere were much more massive: we seem to have witnessed in 1992 aburst of activity with a mass-loss rate greater than 10-8solar mass/yr.
|
Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...79S&db_key=AST
|
Simultaneous UVBY Photometry of 28-ANDROMEDAE
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...273..473R&db_key=AST
|
Statistical Analysis of a Sample of Spectroscopic Binaries Containing Late Type Giants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...271..125B&db_key=AST
|
Zeta-Aurigae Type Binaries
Not Available
|
Wind driven mass transfer in interacting binary systems
Quantitative estimates for conditions governing wind-driven masstransfer in interacting binary systems are presented. It is shown that,for a semidetached system in which the lobe-filling star is a red giant,mass loss from this star by the system as a whole can drive masstransfer. If the mass is lost on a sufficiently short time-scale, thiswind-driven mass transfer can dominate over the traditional-nucleardriven mass transfer. If additional angular momentum is lost because theescaping material is forced to corotate out to some Alfven radius, themass transfer can be driven at an even greater rate. In this case therates of mass transfer and of mass loss can be quantified as functionsof the mass ratio and the Alfven radius. Some numerical models of theexpected evolution are presented and observational predictions areexamined. It is found that the radii of evolved semidetached systems aremore consistent with wind-driven evolution than the traditionalnuclear-driven Riche-lobe overflow.
|
The zeta-Aurigae-type binary AL Velorum
Not Available
|
Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)
This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
|
The long-period binary AL Velorum - The atmospheric eclipse of a bright K0 giant
The properties of the AL Vel binary system, a Zeta Aur system containinga B dwarf and a bright K0 giant, are reviewed with reference to IUEobservations of its atmospheric eclipse and eclipse of the accretiondisk around the B-dwarf component. It is found that the conditions inthe chromosphere are rather similar to those in the Zeta Aursupergiants, once allowance is made for the different sizes and scaleheights involved. The conditions for Mg II suppression in the windthrough ionization by the B star is discussed, and it is found thatradiative excitation and subsequent ionization will suffice for theconditions encountered in the AL Vel system.
|
Eclipsing binaries in open clusters. I - Preliminary study
A preliminary list of suspected eclipsing binaries in open clusters ispresented. The period, the mass ratio, the correlation between the massratio and cluster age, and the periodicity diagram are investigated.
|
Catalogue of Eclipsing and Spectroscopic Binary Stars in the Regions of Open Clusters
Not Available
|
A uvby, beta photometric survey of southern hemisphere
A uvby, beta photometric study of southern hemisphere eclipsing binarystars has been undertaken at Cerro Tololo Inter-American Observatory.The standardized colors and V magnitudes for 288 binaries at quadratureand/or at minimum are presented, along with an indication of theaccuracy of the standardization and photometry. Discussions of theresolving time of the pulse-counting photometers and of the atmosphericextinction at CTIO are included.
|
IAU Archives of Unpublished Observations of Variable Stars
Not Available
|
I.A.U. Archives of Unpublished Observations of Variable Stars - 1979-1981 Data
Not Available
|
Information on the Photoelectric Observations of Variable Stars Deposited at Odessa-Astronomical
Not Available
|
Two Eclipses of Al-Velorum
Abstract image available at:http://adsabs.harvard.edu/abs/1980MNRAS.193..867W
|
A catalogue of parameters for eclipsing binaries
Not Available
|
Photoelectrically-Neglected Eclipsing Binaries
Not Available
|
INHABITED SKY
