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Phase-dependent X-ray observations of the β Lyrae system. No eclipse in the soft band
Aims.We report on observations of the eclipsing and interacting binaryβ Lyrae from the Suzaku X-ray telescope. This system involves anearly B star embedded in an optically and geometrically thick disk thatis siphoning atmospheric gases from a less massive late B II companion. Methods: Motivated by an unpublished X-ray spectrum from the EinsteinX-ray telescope suggesting unusually hard emission, we obtained timewith Suzaku for pointings at three different phases within a singleorbit. Results: From the XIS detectors, the softer X-ray emissionappears typical of an early-type star. What is surprising is theremarkably unchanging character of this emission, both in luminosity andin spectral shape, despite the highly asymmetric geometry of the system.We see no eclipse effect below 10 keV. The constancy of the softemission is plausibly related to the wind of the embedded B star andThomson scattering of X-rays in the system, although it might be due toextended shock structures arising near the accretion disk as a result ofthe unusually high mass-transfer rate. There is some evidence from thePIN instrument for hard emission in the 10-60 keV range. Follow-upobservations with the RXTE satellite will confirm this preliminarydetection.
| A period study and light-curve synthesis for the Algol-type semidetached binary XXCephei
We obtained CCD photometric observations of the Algol-type semidetachedbinary XXCephei (XXCep) during 15 nights from 2002 September 17 to 2003February 2, and also on 2005 January 21. Except for those data taken onthe last night of the concentrated observing season, the 3881measurements were obtained over an interval of only 106 nights. Fromthese data, four new times of minimum light were calculated. The (O- C)diagram formed from all available timings, and thus the orbital periodof the system, can be partly represented as a beat effect between twocyclical variations with different periods (yr, yr) and amplitudes(K1=0.015d, K2=0.103d), respectively. Bothphysical and non-physical interpretations of these cycles wereinvestigated. The long-term sinusoidal variation is too long formagnetic cycling in solar-type single and close binary stars. Inaddition, we have studied the effect of a possible secular periodvariation. By analysing the residuals from our Wilson-Devinney (WD)binary model, we found small light variations with a period of 5.99dwith amplitudes growing toward longer wavelengths. We think that theseoscillations may be produced by instabilities at the systemicL1 point (also occupied by the point of the cool star) andthat these instabilities are, in turn, caused by non-uniform andsporadic convection. There is also a short-period oscillation of about45min in the WD light residuals that is attributed to accretion on tothe mass-gaining primary component from a feeble gas stream originatingon the cool donor star.
| Indirect imaging of an accretion disk rim in the long-period interacting binary W Crucis
Context: .Light curves of the long-period Algols are known for theircomplex shape (asymmetry in the eclipse, light variations outside theeclipse, changes from cycle-to-cycle), but their interpretation is notpossible in the standard model of binary stars. Aims: . Wedetermined that complex structures present in these active Algol systemscould be studied with the eclipse-mapping method that was successfullyapplied to the new 7-color photometric observations in the Geneva systemof W Cru, belonging to the isolated group of these active Algols.Methods: . Several cycles of this long-period (198.5 days) eclipsingbinary were covered by observations. We used a modified Rutten'sapproach to the eclipse-mapping. The optimization of the system'sparameters and the recovery of the disk intensity distribution areperformed using a genetic algorithm (GA). Results: .The finding ofa primary (hot) component is hidden in thick accretion disk confirmsprevious solutions. The mass of the primary component, M1 =8.2 Mȯ, indicates that it is a mid-B type star. Themass-losing component fills its critical lobe, which, for the system'sparameters, means it is a G-type supergiant with a mass M2 =1.6 Mȯ. The disk is very extended geometrically, and itsouter radius is about 80% of the primary's critical lobe. Areconstructed image reveals the rather clumpy and nonuniform brightnessdistribution of an accretion disk rim in this system that is seen almostedge-on. This clumpiness accounts for light curve distortions andasymmetries, as well as for secular changes.
| UBVRI polarimetry of the massive interacting binary SX Cassiopeiae: modeling the electron-scattering circumstellar envelope
Aims.We perform a study of the structure, density, and distribution ofionized circumstellar gas in the strongly interacting binary SX Cas. Methods: .We apply our new model codes for electron scattering incircumstellar matter to analyze a previously unpublished, extensivelinear polarization data set for SX Cas, collected during foursuccessive observing periods in 1981-84 at the Crimean AstrophysicalObservatory. These data are complemented by our polarizationobservations carried out in 2000 and 2005 with the KVA-60 telescope atLa Palma. Results: .A clear, phase-locked pattern of polarizationvariations over the 36.6-day orbital period is revealed in each season,showing significant 1st and 2nd harmonic Fourier components andpronounced effects in the U and B bands at the primary eclipse, when thehot component and the surrounding circumstellar matter are obscured bythe companion star. Seasonal variability is also found, but the majorfeatures of the polarization curves are well explained by a model withan extended scattering region on the trailing side of the accretingstar, where the stream from the companion hits the accretion disk. Nosignificant polarized flux is detected from the disk. We interpret thisas being due to multiple scattering and strong absorption effects in theoptically thick medium, which reduce the polarization of the lightemerging from the disk to low levels. The modeled scattering region isabove the orbital plane by about 10°, as seen from the center of themass gainer. We attribute this to dominant electron scattering takingplace on the upper side of an optically and geometrically thickaccretion disk seen at an inclination i ˜ 78° by theobserver.
| 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.
| Polarimetric Study of the Massive Interacting Binary W Serpentis: Discovery of High-Latitude Scattering Spot/Jet
We present multicolor (UBVRI) polarimetry and additional B-band CCDpolarimetry of the peculiar, strongly interacting binary W Ser, withgood coverage over the 14.16 day orbital period in the three observingseasons 2001-2003. An interesting finding is that the first harmonicdominates in polarization variations over the binary cycle in eachseason, indicating that the main contribution to the polarized flux iscoming from a localized region away from the orbital plane. We apply ournew model codes for electron scattering in circumstellar matter tointerpret the data and find that a ``spot or jet'' like region atlatitude φ~65deg has clearly the best signal-to-noiseratio (>30) among the detected scattering components. Significantshell and stream components are also found, but no disk is seen in thepolarized light. The upper limits for the total number of free electronsin an optically thin scattering disk are an order of magnitude lowerthan in the spherical shell around the primary star. A possible reasonis that the accretion disk is optically thick and has a clearly definedand visible pseudophotosphere. Multiple scattering and absorptioneffects in an optically thick regime reduce the polarization of theobserved light to small levels. Scattering from optically thin parts ofthe circumstellar matter, the shell, the stream, and the high-latitudespot/jet, possibly associated with optically thin polar regions of theaccretion disk, dominates in the observed polarization of W Ser.
| Infrared Photometry for Five Close Binary Systems
We present the JHKLM photometry for five close (W Ser) binary systemsobtained in the period 1996 2004. Positive phase shifts (with respect ofthe adopted ephemerides) have been found in the orbital infrared lightcurves for three binaries, RX Cas, KX And, and β Lyr; the rates ofincrease in their periods are 3.5 × 10-4, 1.6 ×10-3, and 1.4 × 10-4 days yr-1, respectively. We haveperformed the spectral classification of the components of the binariesunder study and estimated their parameters.
| G287.84-0.82: an infrared star cluster in the Carina nebula
We have studied the properties of an infrared cluster embedded in thegas and dust of the southern part of the Carina nebula (NGC 3372), wherethe probable existence of current star formation has already beenpredicted. We used mid-infrared (A and C bands) and near-infrared(JHKs) images from the Midcourse Space Experiment and theTwo-Micron All-Sky Survey, respectively, combined with an opticalHα narrow-band filter image obtained at the Cerro TololoInter-American Observatory. The infrared star cluster has at least 17members, and its parameters, radius and stellar density are in very goodagreement with high- to intermediate-mass star formation scenarios. Thedetected infrared sources have roughly the same intrinsic infraredexcess determined from their position in colour-colour andcolour-magnitude diagrams, suggesting that these objects could berelated to pre-main-sequence stars of high to intermediate mass.Furthermore, we present a low-dispersion spectrum of the LS 1883 (O9.5V)star located near the centre of the infrared cluster. The position ofthis object in the colour-colour and colour-magnitude infrared diagramslies close to the reddening vector of a zero-age main-sequence O9Vspectral-type star, and it seems to be the first star of this cluster toemerge. All these facts are consistent with the current star-formingscenarios associated with highly embedded star clusters.
| 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.
| Up-to-Date Linear Elements of Eclipsing Binaries
About 1800 O-C diagrams of eclipsing binaries were analyzed and up-todate linear elements were computed. The regularly updated ephemerides(as a continuation of SAC) are available only in electronic form at theInternet address: http://www.as.ap.krakow.pl/ephem/.
| Catalogue of Algol type binary stars
A catalogue of (411) Algol-type (semi-detached) binary stars ispresented in the form of five separate tables of information. Thecatalogue has developed from an earlier version by including more recentinformation and an improved layout. A sixth table lists (1872) candidateAlgols, about which fewer details are known at present. Some issuesrelating to the classification and interpretation of Algol-like binariesare also discussed.Catalogue is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/417/263
| The WR+OB Progenitor RY Scuti: Intensive Spectroscopy of Its Compact Double-Ring Nebula
We present a detailed spectroscopic analysis of the peculiar nebulaaround RY Scuti using data from the Space Telescope Imaging Spectrograph(STIS) and various ground-based observatories. This massive contactbinary may represent a rapid evolutionary phase in transition to ashort-period WR+OB system, and it is surrounded by a young nebula withunusual geometry. The ionized nebula is only about 1" across, so STIShas allowed us to spatially resolve the spectrum of the star from itscircumstellar nebula for the first time. Combining STIS data withground-based spectra at optical and infrared wavelengths solves somegeometric ambiguities posed by previous images and reveals the kinematicrelationship between the nebular geometry and RY Scuti's complexemission-line profiles. We offer a new determination of the systemicvelocity of 20+/-3 km s-1, and we estimate the distance to RYScuti as 1.8+/-0.1 kpc. Nebular lines show subtle phase-dependentvariability in addition to expected changes in equivalent width due toeclipses of stellar continuum. These changes in equivalent width yieldan updated ephemeris, but a previously suggested period change is stilluncertain after considering these new data. The nebula contains roughly0.003 Msolar of material that is He- and N-rich and probablyO-deficient compared to solar abundances, indicating that CNO-processedmaterial has reached the surface in at least one component of the binarysystem. Diagnostic line ratios suggest that the electron density andtemperature in the nebula are 2×105 cm-3 and~9500 K, respectively. There are concentrated regions of higher densityas well; emission knots seen around the rings suggest that commonenvelope mass loss during massive contact binary evolution may becharacterized by strong azimuthal asymmetry and sporadic mass ejectionevents. Based on observations made 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 NAS 5-26555.
| Variability of the Hα spectral line in the interacting binary AX Monocerotis
The interacting binary system AX Mon (K-giant + B(e)star) has been observed at the Tartu Observatory, Estonia, from 1985 to2000. In the present paper, mostly the behaviour of the hydrogenHα line from 1996 to 2000 is investigated. We have found that theHα profiles are variable on time scales from hours to years, withmain features appearing around the conjunctions of the stars (K-star infront). Those features include weakening of the main absorptioncomponent of the P Cygni like profile and appearance of additionalabsorption and/or emission components. Occasionally, the Hα lineas a whole shifts on the wavelength scale. All those effects seem tooccur much stronger at every second conjunction, which we propose tocall ``strong'' conjunctions. We propose that this variability is due toa gas cloud close to the Be star. This cloud is a region, where a streamof matter from the K-giant collides with the circumstellar gas from theBe-star. The mass transfer process seems to have become more unstablethan in 1960s. It is possible that a cyclic behaviour of the Hαline with a periodicity of about two orbital periods is present.
| Eclipsing Binary Stars: Past, Present, and Future
A brief history of eclipsing binary star light curve analysis and anoverview of the current state of affairs is given. The photometricsearches for extra-solar planets in the next few years will eventuallyresult in millions of light curves and such volumes of data will requirethe efforts of amateur astronomers in their analysis. This article is athinly veiled plea to AAVSO members to join the current efforts of a fewAAVSO members in the observation and analysis of eclipsing binary stars.
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| From OAO2 to HST. A quarter of a century of ultraviolet astronomy.
Not Available
| UBVI photometry and polarimetry of V373 Cas.
Not Available
| The strongly constrained interacting binary BY Crucis.
We discuss spectroscopic and photometric observations (UV to IR) of BYCrucis, a new bright member of the interacting binaries of the WSerpentis class. The orbital period is 106.4days, and the mass functionamounts to 5.92Msun_. The primary is an early-F supergiantwhich fills its Roche lobe; the massive secondary is hidden inside athick accretion disk, which is probably the dominant light source in theultraviolet. The observed variations in the photometric lightcurves arecaused mainly by ellipsoidal variations. It is unlikely that an eclipseoccurs. A particularly interesting circumstance is that BY Cru is aprobable member of a visual multiple system which contains anotherevolved star. This circumstance enables us to estimate with someaccuracy the age of the interacting binary and the initial mass of theprimary. The history of this binary is then much more constrained thanfor the other W Serpentis stars. Also taking into account the fact thatthe binary has avoided Case C Roche lobe overflow, we determine upperand lower bounds for the initial and present masses of both components,and conclude that mass transfer has only been moderatelynon-conservative.
| 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.
| Goddard High-Resolution Spectrograph Observations of the Interacting Binary System W Serpentis
Abstract image available at:http://adsabs.harvard.edu/abs/1995ApJ...447..401W
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Binary-star light curve models
The historical development of binary-star light-curve models is tracedfrom the early 1900s to the present, with emphasis on recent progress. Amajor break with tradition occurred about 1970 when physical models,based on equipotentials and made possible by fast computers, replacedgeometrical models. Physical models have been improving in accuracy,efficiency, generality, and user friendliness. Further improvements canbe expected. Astrophysical advances due to the new models range from newways to estimate mass ratios and rotation rates to confirmation oftheoretical predictions about the structure of W Ursae Majoris stars andbehavior of irradiated convective envelopes. The morphology of closebinaries, including extensions to nonsynchronous rotation and orbitaleccentricity, is interwoven with physical models and their applications.The origins and influence of the four morphological types -- detached,semidetached, overcontact, and double contact -- are inseparable fromthe development of light-curve models. Parameter adjustment is an activearea, with contributions on Differential Corrections, the Marquardtalgorithm, the Simplex algorithm, and other methods for reaching aleast-squares minimum. Solutions with applied constraints andsimultaneous solutions of two or more kinds of observations are cominginto more frequent usage. Observables other than photometric brightnessinclude radial velocity, polarization, photospheric spectral lineprofiles, and spectral distributions due to circumstellar flows. Some ofthe newer models extend into these areas and are leading to new kinds ofobserving programs.
| Investigation of the Emission Line Spectrum of Ry-Scuti - the Circumstellar and Nebular Gaseous Structures
Not Available
| Radio observations of peculiar emission-line Algol binary stars
Twelve peculiar emission-line Algol (PELA) binaries were observed at cmwavelengths. Six of these objects, WW And (tentative), KX And, AM Aur,V644 Mon, DN Ori, and AY Per were detected at the 100 to 400 micro-Jylevel, corresponding to luminosity densities of order 10 exp 17erg/s/Hz. These luminosity densities, combined with nearly flat cmspectra and high brightness temperatures, are consistent with thenonthermal gyrosynchrotron radiation model proposed as the result ofobservations from the previous PELA survey. Also, the star V367 Cyg wasreobserved at thirteen different orbital phases; no variability wasfound within the errors. V367 Cyg's lack of variability andwell-determined average spectral index, however, imply the possibilityof a different emission mechanism, thermal bremsstrahlung, although thenonthermal model cannot be entirely ruled out. The characteristicbrightness temperature of thermal bremsstrahlung is only about 10,000 K,which means that the radius of the emission region would have to be muchlarger than previously assumed, about 10 AU. Suggestions for furtherobservations of all previously observed PELAS are presented in order todetermine the correct emission mechanism.
| New optical spectrographic observations of W Serpentis
New spectroscopic data of the peculiar interacting binary system WSerpentis in the region of H-alpha and H-beta are being reported,through the phase interval 0.95-0.16 p. We recognize the six sets oflines described by Sahade and Struve (1957). In addition to the Fe IIconcentration lines in the blue region, reported in earlier work, wefind the presence of O I concentration in the red that confirms theexistence of a low density region surrounding the system, as suggestedby Sahade and Struve (1957). We confirm the difficult interpretation offeatures in the Mg II 4481 A region. We present radial velocities fromHe I for the first time.
| Speckle observations of visual and spectroscopic binaries. IV
This is the fourth paper of this series giving results of speckleobservations for 22 visual and 161 spectroscopic binaries. Theobservation was carried out by using the 212 cm telescope of San PedroMartir Observatory in Mexico on 7 nights from July 20 to July 26, 1991.We obtained fringes in power spectra of 19 visual and 11 spectroscopicbinaries (6 newly resolved ones) with angular separation larger than0.06 arcsec. We introduced a new ICCD TV camera in this observation, andwere able to achieve the diffraction-limit resolution of the 212 cmtelescope.
| Speckle observations of visual and spectroscopic binaries. III
This is the third paper of this series giving results of speckleobservations carried out for seven visual and 119 spectroscopic binariesat seven nights from May 20 to May 27, 1989, and for 30 visual and 272spectroscopic binaries at 12 nights from June 11 to June 15, and fromAugust 28 to September 3, 1990, using the 212-cm telescope at San PedroMartir Observatory in Mexico. Fringes in the lower spectrum of 31 visualand spectroscopic binaries with angular separation larger than 21 arcsecare obtained. Additionally to two spectroscopic binaries, HD41116 andHD206901, named in the second paper of this series, six spectroscopicbinaries are found each of which has the third component starsurrounding two stars of spectroscopic binary having periodic variationof radial velocity.
| Spectroscopic Observations of the W Serpentis Binary System with the HST Goddard High Resolution Spectrograph
Not Available
| Close binaries observed polarimetrically
Not Available
| Energy distribution in the spectrum of RX CAS
The spectral energy distribution for the envelope around the maincomponent in the RX Cas system is investigated on the basis of 22spectrograms with a dispersion of 166 A/mm. The spectral class of theenvelope corresponds to gG2-5.
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