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Nochmal SZ Cam.
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| Young Stars in the Camelopardalis Dust and Molecular Clouds. I. The Cam OB1 Association
The distribution of dust and molecular clouds in the direction ofGalactic longitudes 132--158° and latitudes ± 12\degr\ isinvestigated. The maps of dust distribution in the area were plottedfrom the following surveys: the star counts in the DSS I database byDobashi et al. (2005), the survey of the average infrared color excessesby Froebrich et al. (2007) and the thermal dust emission survey at 100μ m by Schlegel et al. (1998). The distribution of molecular cloudswas taken from the whole sky CO survey by Dame et al. (2001). All thesesurveys show very similar cloud patterns in the area. Using the radialvelocities of CO, the distances to separate clouds are estimated. Arevised list of the Cam OB1 association members contains 43 stars andthe open cluster NGC 1502. 18 young irregular variable and Hαemission stars are identified in the area. All this proves that the starforming process in the Camelopardalis clouds is still in progress.
| A high-resolution spectroscopy survey of β Cephei pulsations in bright stars
We present a study of absorption line-profile variations in early-B typenear-main-sequence stars without emission lines. We have surveyed atotal of 171 bright stars using the Nordic Optical Telescope (NOTSA),William Herschel Telescope (ING) and Coudé Auxiliary Telescope(ESO). Our sample contains 75% of all O9.5-B2.5 III-V non-emission-linestars brighter than 5.5 mag. We obtained high signal-to-noise,high-resolution spectra of the SiIII λ4560 triplet - for 125stars of our sample we obtained more than one spectrum - and examinedthese for pulsational-like line-profile variations and/or structure. Weconclude that about half of our sample stars show evidence forline-profile variations (LPV). We find evidence for LPV in about 65% ofour sample stars brighter than V=5.5. For stars with rotationalbroadening V sin i 100 km s-1, we find evidence for LPVin about 75% of the cases. We argue that it is likely that these LPV areof pulsational origin, and that hence more than half of thesolar-neighbourhood O9.5-B2.5 III-V stars is pulsating in modes that canbe detected with high-resolution spectroscopy. We detected LPV in 64stars previously unknown to be pulsators, and label these stars as newβ Cep candidates. We conclude that there is no obvious differencein incidence of (pulsational) LPV for early-B type near-main-sequencestars in binaries or in OB associations, with respect to single fieldstars.
| 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.
| SZ Camelopardalis - ein Bedeckungsveraenderlicher in einem gravitativen Vierfachsystem.
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| On the Hipparcos parallaxes of O stars
We compare the absolute visual magnitude of the majority of bright Ostars in the sky as predicted from their spectral type with the absolutemagnitude calculated from their apparent magnitude and the Hipparcosparallax. We find that many stars appear to be much fainter thanexpected, up to five magnitudes. We find no evidence for a correlationbetween magnitude differences and the stellar rotational velocity assuggested for OB stars by Lamers et al. (1997, A&A, 325, L25), whosesmall sample of stars is partly included in ours. Instead, by means of asimulation we show how these differences arise naturally from the largedistances at which O stars are located, and the level of precision ofthe parallax measurements achieved by Hipparcos. Straightforwardlyderiving a distance from the Hipparcos parallax yields reliable resultsfor one or two O stars only. We discuss several types of bias reportedin the literature in connection with parallax samples (Lutz-Kelker,Malmquist) and investigate how they affect the O star sample. Inaddition, we test three absolute magnitude calibrations from theliterature (Schmidt-Kaler et al. 1982, Landolt-Börnstein; Howarth& Prinja 1989, ApJS, 69, 527; Vacca et al. 1996, ApJ, 460, 914) andfind that they are consistent with the Hipparcos measurements. AlthoughO stars conform nicely to the simulation, we notice that some B stars inthe sample of \citeauthor{La97} have a magnitude difference larger thanexpected.
| A Galactic O Star Catalog
We have produced a catalog of 378 Galactic O stars with accuratespectral classifications that is complete for V<8 but includes manyfainter stars. The catalog provides cross-identifications with othersources; coordinates (obtained in most cases from Tycho-2 data);astrometric distances for 24 of the nearest stars; optical (Tycho-2,Johnson, and Strömgren) and NIR photometry; group membership,runaway character, and multiplicity information; and a Web-based versionwith links to on-line services.
| Speckle Interferometry at the US Naval Observatory. IX.
The results of 3056 speckle interferometric observations of doublestars, made with the 26 inch (66 cm) refractor of the US NavalObservatory, are presented. Each speckle interferometric observation ofa system represents a combination of over a thousand short-exposureimages. These observations are averaged into 1675 mean relativepositions and range in separation from 0.19" to 45.21", with a medianseparation of 2.99". This is the ninth in a series of papers presentingmeasures obtained with this system and covers the period 2002 January 1through 2002 December 29. Included in these data are 28 older measureswhose positions were previously deemed possibly aberrant but are nolonger classified this way following a confirming observation. Nine ofthese systems have new orbital elements, which are presented here aswell.
| Masses and other parameters of massive binaries
Binary stars provide us with the means to measure stellar mass. Here Ipresent several lists of known O-type stars with reliable mass estimatesthat are members of eclipsing, double-lined spectroscopic binaries. Themasses of young, unevolved stars in binaries are suitable for testingthe predictions of evolutionary codes, and there is good agreementbetween the observed and predicted masses (based upon temperature andluminosity) if the lower temperature scale from line-blanketed modelatmospheres is adopted. A final table lists masses for systems in awide variety of advanced evolutionary stages.
| Confirmation of a Double Nature of the Third Body in SZ Cam
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| Spectroscopy of four early-type eclipsing binaries
New spectroscopic data were obtained for the early-type binariesV337 Aql, V649 Cas, V382Cyg, and V431 Pup. Their radial velocitycurves are presented. These are the first such data for V337Aql and V431 Pup. In the case ofV382 Cyg, our data confirm previously obtainedresults. Especially for V649 Cas our radial velocitycurve yields important new implications for the component masses: thedetection of third body lines, which are blended with the lines of theprimary component, solves the problem of the unacceptably small massesformerly deduced for this binary; now we determine masses closer to thevalues expected for spectral type B 0. V431 Pup is animportant object, because it is a new member of the small group ofearly-type eclipsing binaries with an evolved component. A publishedlight curve of V337 Aql is solved by the MORO code, and systemparameters are derived. The period of V649 Cas isfound to be variable, and a more accurate period is calculated forV431 Pup. Based on observations collected at theEuropean Southern Observatory, La Silla, Chile, and at theGerman-Spanish Astronomical Center (DSAZ), Calar Alto, operated by theMax-Planck-Institut für Astronomie Heidelberg jointly with theSpanish National Commission for Astronomy.
| The evolution of the theoretical bolometric albedo in close binary systems
Until now the bolometric albedo in close binary systems was computedonly for a few, and sometimes unrealistic cases. In this paper wepresent, for the first time, the evolution of the bolometric albedo as afunction of the external flux, of the geometry and of the evolutionarystatus of an irradiated star. A new numerical method, based on theisoentropy at the bottom of the perturbed and the non-irradiatedhemispheres, is introduced. A variant of this numerical method wasalready used by us to predict gravity darkening exponents and it isappropriate to radiative and convective envelopes. The procedure canalso combine consistently the coupling interior-envelope-atmospheresmodels. The theoretical predictions are compared with the inferredvalues of the bolometric albedo available in the literature whenpossible. A theoretical transition zone is predicted forlogTeff~3.8 which coincides approximately with that forgravity darkening exponents. This value cannot be confirmed by theobservations as a result of the high scattering of the empirical points.More extensive and careful analysis of light curves of eclipsingbinaries is needed in order to clarify the scenario.
| Optical spectroscopy of XMEGA targets in the Carina Nebula - III. The multiple system Tr 16-104 (≡CPD -59° 2603)
We discuss the orbital elements of the multiple system Tr 16-104 whichis usually believed to be a member of the open cluster Trumpler 16 inthe Carina complex. We show that Tr 16-104 could be a hierarchicaltriple system consisting of a short-period (2.15d) eclipsing O7V+O9.5Vbinary bound to a B0.2 IV star. Our preliminary orbital solution of thethird body indicates that the B star most probably describes aneccentric orbit with a period of ~285 or ~1341d around the close binary.Folding photometric data from the literature with our new ephemerides,we find that the light curve of the close binary exhibits rather narroweclipses indicating that the two O stars must be well inside their Rochelobes. Our analysis of the photometric data yields a lower limit on theinclination of the orbit of the close binary of i>=77°. Thestellar radii and luminosities of the O7 V and O9.5 V stars aresignificantly smaller than expected for stars of this spectral type. Ourresults suggest that Tr 16-104 lies at a distance of the order of 2.5kpcand support a fainter absolute magnitude for zero-age main-sequence Ostars than usually adopted. We find that the dynamical configuration ofTr 16-104 corresponds to a hierarchical system that should remain stableprovided that it suffers no strong perturbation. Finally, we also reportlong-term temporal variations of high-velocity interstellar Caiiabsorptions in the line of sight towards Tr 16-104.
| High-mass binaries in the very young open cluster NGC 6231. Implication for cluster and star formation
New radial-velocity observations of 37 O- and B stars in the very youngopen cluster NGC 6231 confirm the high frequency of short-periodspectroscopic binaries on the upper main sequence. Among the 14 O-typestars, covering all luminosity classes from dwarfs to supergiants, 8 aredefinitively double-lined systems and all periods but one are shorterthan 7 days. Several additional binaries have been detected among theearly B-type stars. NGC 6231 is an exceptional cluster to constrain thescenarios of cluster- and binary-star formation over a large range ofstellar masses. We discuss the evidences, based on NGC 6231 and 21 otherclusters, with a total of 120 O-type stars, for a clear dichotomy in themultiplicity rate and structure of very young open clusters containingO-type stars in function of the number of massive stars. However, wecannot answer the question whether the observed characteristics resultfrom the formation processes or from the early dynamical evolution.
| The early-type multiple system QZ Carinae
We present an analysis of the early-type quadruple system QZ Car,consisting of an eclipsing and a non-eclipsing binary. The spectroscopicinvestigation is based on new high dispersion echelle and CAT/CESspectra of H and He lines. The elements for the orbit of thenon-eclipsing pair could be refined. Lines of the brighter component ofthe eclipsing binary were detected in near-quadrature spectra, whilesignatures of the fainter component could be identified in only fewspectra. Lines of the primary component of the non-eclipsing pair and ofboth components of the eclipsing pair were found to be variable inposition and strength; in particular, the He ii 4686 emission line ofthe brighter eclipsing component is strongly variable. An ephemeris forthe eclipsing binary QZ Car valid at present was derived Prim. Min. =hel. JD 2448687.16 + 5fd9991 * E. The relative orbit of the two binaryconstituents of the multiple system is discussed. In contrast to earlierinvestigations we found radial velocity changes of the systemicvelocities of both binaries, which were used - together with an O-Canalysis of the expected light-time effect - to derive approximateparameters of the mutual orbit of the two pairs. It is shown that thisorbit and the distance to QZ Car can be further refined by minima timingand interferometry. Based on observations collected at the EuropeanSouthern Observatory, La Silla, Chile.
| Classification and properties of UV extinction curves
The catalog of Savage et al. (\cite{ref27}) reporting colour excesses of1415 stars from ANS photometry offers the opportunity to deeplyinvestigate the characteristics of UV extinction curves which differfrom the standard extinction of the diffuse interstellar medium. To thisaim we have selected a sample of 252 curves, which have been comparedwith the relations derived by Cardelli et al. (\cite{ref4}; CCM in thefollowing) for a variety of R_V values in the range 2.4-5 and have beenclassified as normal if they fit at least one of the CCM curves oranomalous otherwise. We find that normal curves with small R_V are justas numerous as those with large R_V. The anomalous objects are arrangedinto two groups according to the strength of the bump at 0.217 mu . Fora given value of c_2 this increases along the sequence: type Aanomalous, normals and type B anomalous, suggesting that this sequenceshould correspond to an increase of the amount of small grains along thesightline. Considerations concerning the environmental characteristicsindicate that the anomalous behaviour is not necessarily tied to theexistence of dense gas clouds along the line of sight.
| 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.
| On the Variability of O4-B5 Luminosity Class III-V Stars
We investigate the Hipparcos Satellite photometry of O4-B5 luminosityclass III-V stars. Some for which further study is desirable areidentified. These stars in general are more variable than cooler stars
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 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
| UBVR-Photometry of the Eclipsing Binary SZ Cam
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| V606 Centauri: an early-type eclipsing contact binary
We present a spectroscopic and photometric analysis of the early-typeeclipsing binary V606 Cen. Based on new high-resolution CCD spectra thefirst radial velocity curve of this system is given, which allows for anaccurate determination of radial velocity amplitudes (K_1=181.8 km s(-1), K_2=345.2 km s(-1) ) and the spectroscopic mass ratio q_spec=0.527.Moreover, equivalent widths are listed. The line strengths of He i 4922show strong variations with the orbital phase, related to the so-called(and hitherto unexplained) ``Struve-Sahade effect". In this context,some aspects concerning the determination of equivalent widths in closebinary systems are discussed, with special reference to the influence ofthe ellipsoidal light variations. For the first time, photoelectric UBVlight curves of V606 Cen are presented, which were solved with the MOROcode, based on the Wilson-Devinney model. The first set of solutions wasachieved with effective temperatures according to the previous spectralclassification B1-2 Ib/IIb, but the derived absolute dimensions, surfacegravities, as well as an investigation of the equivalent widths led to arevision of the spectral type. We now suggest B0-0.5 V for the primary,and B2-3 V for the secondary component, respectively. Using thecorresponding effective temperatures, another light curve analysis wasperformed, yielding the following absolute dimensions: M_1=14.7 M_sun,M_2=8.0 M_sun, R_1=6.8 R_sun, R_2=5.2 R_sun, log L_1/L_sun=4.48, and logL_2/L_sun=3.74. In all cases, a contact configuration is found. Theevolutionary state of V606 Cen is discussed in the light of modernevolutionary grids. It turns out that this contact system was formedduring the slow phase of case A mass transfer after reversal of its massratio. In this respect it is similar to other early-type contactbinaries such as V382 Cyg, V701 Sco or RZ Pyx. Based on observationscollected at the European Southern Observatory, La Silla, Chile
| Interacting OB star binaries: LZ Cep, SZ Cam and IU AUR
New spectroscopic observations of three O+O binary stars (LZ Cep, SZ Camand IU Aur), obtained over a number of years at the DominionAstrophysical Observatory, are analysed using state-of-the-artcross-correlation techniques to produce radial velocity curves. Theseresults are combined with new (LZ Cep) and published (SZ Cam and IU Aur)photometry to yield masses, temperatures, radii and luminosities. Wefind that LZ Cep is a semi-detached system, in agreement with theresults of Howarth et al., with the secondary star filling its Rochelobe. We find a distance modulus of 9.6+/-0.2, which is slightly smallerthan the distance modulus to Cep OB2 (=9.9).The reddening of LZ Cep isalso at the lower end of the cluster range, suggesting that the binaryis located on the near side of the cluster. SZ Cam is a triple system,and we are able to measure the radial velocities of the three componentsthat are observed in the absorption lines. A light-curve solutionemploying our new mass ratio shows that the short-period binary isdetached. The third body emits about 40 per cent of the radiation fromthe system, and is probably a binary itself. The distance modulus for SZCam (=9.88) is in good agreement with that of its parent cluster NGC1502 (=9.71). IU Aur is another triple system, although we are unable tofind spectroscopic evidence for the tertiary. The close binary issemi-detached, with the secondary filling its Roche lobe. The distancemodulus of the system is 11.0, which is in approximate agreement withthat of the Aur OB1 association (=10.6+/-0.2). We note that the currentmodels for interacting massive binaries all assume case B mass transfer,in which the mass-loser becomes a Wolf-Rayet star. Case A mass-transfermodels (in which the mass-loser fills its Roche lobe while still on themain sequence) are required in order to see whether or not they canexplain the observed properties of these interacting systems.
| SZ Camelopardalis - an early-type eclipsing binary embedded in a multiple system
We present a spectroscopic and photometric analysis of a complexmultiple system: the early-type eclipsing binary SZ Cam (O9 IV + B0.5 V)is physically bound to a third body, which itself is a close binary;this quadruple system has a visual companion, which shows evidence forduplicity as well. A careful deconvolution of spectral lines in our CCDspectra yields rv curves of the SB2 system (K_1 = 180 km s(-1) , K_2 =261 km s(-1) ; P = 2fd 6984) and of its SB1 companion (K_{1{,T}} = 25 kms(-1) ; P 2fd 7966). UBV light curves of Kitamura & Yamasaki (1970)are reanalyzed and absolute dimensions of the eclipsing pair arederived. Both components of this close detached binary are overluminousfor their masses. The photometric solution suggests third light of ~20-30%, which confirms the spectroscopic and speckle interferometricdetection (Mason 1995) of the third component. The observed light timeeffect encompasses the long period range to ~ 50-60 years. Comparison ofcalculated orbits with the speckle interferometric result yields adistance of 1050 pc, which is ~ 10% larger than the value derived fromthe absolute bolometric magnitude, and ~ 20% above the photometricdistance of the open cluster NGC 1502. The minimum mass of the thirdcomponent is 20-30 M_ȯ, depending on the long orbital period andinclination assumed. This high mass supports the binary nature of thethird body. An analysis of the spectra of the visual companion ADS 2984A confirms its binarity. Based on observations collected at theGerman-Spanish Astronomical Centre, Calar Alto, operated by theMax-Planck-Institut für Astronomie, Heidelberg, jointly with theSpanish National Commission for Astronomy
| ICCD speckle observations of binary stars. XIX - an astrometric/spectroscopic survey of O stars
We present the results of a speckle interferometric survey made with theCHARA speckle camera and 4 m class telescopes of Galactic O-type starswith V less than 8. We can detect with the speckle camera binaries inthe angular separation range 0.035-1.5 arcsec with delta M less than 3,and we have discovered 15 binaries among 227 O-type systems. We combinedour results on visual binaries with measurements of wider pairs from theWashington Double Star Catalog and fainter pairs from the HipparcosCatalog, and we made a literature survey of the spectroscopic binariesamong the sample. We then investigated the overall binary frequency ofthe sample and the orbital characteristics of the known binaries.Binaries are common among O stars in clusters and associations but lessso among field and especially runaway stars. There are many triplesystems among the speckle binaries, and we discuss their possible rolein the ejection of stars from clusters. The period distribution of thebinaries is bimodal in log P, but we suggest that binaries with periodsof years and decades may eventually be found to fill the gap. The massratio distribution of the visual binaries increases toward lower massratios, but low mass ratio companions are rare among close,spectroscopic binaries. We present distributions of the eccentricity andlongitude of periastron for spectroscopic binaries with ellipticalorbits, and we find strong evidence of a bias in the longitude ofperiastron distribution.
| Physical parameters of multiple systems like the Trapezium of early spectral types, derived from uvby-beta photometry. II.
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| Application of the KOREL cross-correlation technique to radial-velocity measurements of early-type close binaries.
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| The three-body system V 505 Sagittarii.
It is known that the period of the eclipsing binary V 505 Sgr changes,and that the changes can be explained - at least partly - by alight-time effect. The system is also known as a speckle binary. In thispaper parameters of the third body orbit are suggested in order toexplain both sets of data. Some discrepancies in the size of the orbitand radial velocity data remain. Next periastron passage should be at1998.9.
| Cross Identification in the Region of Cluster NGC 1502
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114..222W&db_key=AST
| MSC - a catalogue of physical multiple stars
The 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
| Physical parameters of multiple systems like the Trapezium of early spectral types, derived from uvby-beta photometry. I.
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