תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
Absolute properties of BG Ind - a bright F3 system just leaving the main sequence
We present photometric and spectroscopic analysis of the bright detachedeclipsing binary BG Ind. The masses of the components are found to be1.428 ± 0.008 and 1.293 ± 0.008 M&sun; and theradii to be 2.290 ± 0.017 and 1.680 ± 0.038R&sun; for primary and secondary stars, respectively. Spectraand isochrone fittings coupled with colour indices calibration yield[Fe/H]=-0.2 ± 0.1. At an age of 2.65 ± 0.20 Gyr, BG Ind iswell advanced in the main-sequence evolutionary phase - in fact, itsprimary is at TAMS or just beyond it. Together with three similarsystems (BK Peg, BW Aqr and GX Gem), it offers an interestingopportunity to test the theoretical description of overshooting in thecritical mass range 1.2-1.5 M&sun;. Based in part on dataobtained at the South African Astronomical Observatory.
| Absolute Properties of the Eclipsing Triple Star CO Andromedae: Constraints on Convective Core Overshooting
Accurate absolute properties have been determined for the eclipsingtriple star CO And (F8+F8) based on extensive differential photometryobtained by three robotic observatories and CfA spectroscopy. Theeclipsing binary star orbit is circular with a period of 3.655 days. Thetriple nature of this system is revealed by more than a century oftimings of minimum light, and by the presence of third light in thephotometric orbits. The masses of the eclipsing pair are 1.289 ±0.007 and 1.264 ± 0.007 solar masses, and the corresponding radiiare 1.727 ± 0.021 and 1.694 ± 0.017 solar radii. Thesestars are synchronously rotating and are near the end of theirmain-sequence phase, at an age of about 3.6 Gyr. The much fainter widelyseparated third body appears to have a mass of about 0.8 solar masses.The distance to the system is 377 ± 25 pc.
| Absolute dimensions of eclipsing binaries. XXVIII. BK Pegasi and other F-type binaries: Prospects for calibration of convective core overshoot
Context. Double-lined, detached eclipsing binaries are our main sourcefor accurate stellar masses and radii. In this paper we focus on the1.15-1.70 M? interval where convective core overshoot isgradually ramped up in theoretical evolutionary models. Aims: Weaim to determine absolute dimensions and abundances for the F-typedetached eclipsing binary BK Peg, and to perform a detailed comparisonwith results from recent stellar evolutionary models, including a sampleof previously studied systems with accurate parameters. Methods:uvby light curves and uvby? standard photometry were obtained withthe Strömgren Automatic Telescope, ESO, La Silla, andhigh-resolution spectra were acquired with the FIES spectrograph at theNordic Optical Telescope, La Palma. Results: The 5 fd 49 periodorbit of BK Peg is slightly eccentric (e = 0.053). The two componentsare quite different with masses and radii of (1.414 ± 0.007M?, 1.988 ± 0.008 Rsun) and (1.257± 0.005 M?, 1.474 ± 0.017Rsun), respectively. The measured rotational velocities are16.6 ± 0.2 (primary) and 13.4 ± 0.2 (secondary) kms-1. For the secondary component this corresponds to(pseudo)synchronous rotation, whereas the primary component seems torotate at a slightly lower rate. We derive an iron abundance of [Fe/H] =-0.12 ± 0.07 and similar abundances for Si, Ca, Sc, Ti, Cr andNi. The stars have evolved to the upper half of the main-sequence band.Yonsei-Yale and Victoria-Regina evolutionary models for the observedmetal abundance reproduce BK Peg at ages of 2.75 and 2.50 Gyr,respectively, but tend to predict a lower age for the more massiveprimary component than for the secondary. We find the same age trend forthree other upper main-sequence systems in a sample of well studiedeclipsing binaries with components in the 1.15-1.70 M?range. We also find that the Yonsei-Yale models systematically predicthigher ages than the Victoria-Regina models. The sample includes BW Aqr,and as a supplement we have determined a [Fe/H] abundance of -0.07± 0.11 for this late F-type binary. Conclusions: Wepropose to use BK Peg, BW Aqr, and other well-studied 1.15-1.70M? eclipsing binaries to fine-tune convective coreovershoot, diffusion, and possibly other ingredients of moderntheoretical evolutionary models.Based on observations carried out at the Strömgren AutomaticTelescope (SAT) and the 1.5m telescope (63.H-0080) at ESO, La Silla, andthe Nordic Optical Telescope at La PalmaTables 13-17 are available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/516/A42
| Accurate masses and radii of normal stars: modern results and applications
This article presents and discusses a critical compilation of accurate,fundamental determinations of stellar masses and radii. We haveidentified 95 detached binary systems containing 190 stars (94 eclipsingsystems, and ? Centauri) that satisfy our criterion that the massand radius of both stars be known within errors of ±3% accuracyor better. All of them are non-interacting systems, and so the starsshould have evolved as if they were single. This sample more thandoubles that of the earlier similar review by Andersen (Astron AstrophysRev 3:91-126, 1991), extends the mass range at both ends and, forthe first time, includes an extragalactic binary. In every case, we haveexamined the original data and recomputed the stellar parameters with aconsistent set of assumptions and physical constants. To these we addinterstellar reddening, effective temperature, metal abundance,rotational velocity and apsidal motion determinations when available,and we compute a number of other physical parameters, notably luminosityand distance. These accurate physical parameters reveal the effects ofstellar evolution with unprecedented clarity, and we discuss the use ofthe data in observational tests of stellar evolution models in somedetail. Earlier findings of significant structural differences betweenmoderately fast-rotating, mildly active stars and single stars, ascribedto the presence of strong magnetic and spot activity, are confirmedbeyond doubt. We also show how the best data can be used to testprescriptions for the subtle interplay between convection, diffusion,and other non-classical effects in stellar models. The amount andquality of the data also allow us to analyse the tidal evolution of thesystems in considerable depth, testing prescriptions of rotationalsynchronisation and orbital circularisation in greater detail thanpossible before. We show that the formulae for pseudo-synchronisation ofstars in eccentric orbits predict the observed rotations quite well,except for very young and/or widely separated stars. Deviations dooccur, however, especially for stars with convective envelopes. Thesuperior data set finally demonstrates that apsidal motion rates aspredicted from General Relativity plus tidal theory are in goodagreement with the best observational data. No reliable binary dataexist, which challenge General Relativity to any significant extent. Thenew data also enable us to derive empirical calibrations of M and R forsingle (post-) main-sequence stars above {0.6 M_{odot}}. Simple,polynomial functions of T eff, log g and [Fe/H] yield M and Rwithin errors of 6 and 3%, respectively. Excellent agreement is foundwith independent determinations for host stars of transiting extrasolarplanets, and good agreement with determinations of M and R from stellarmodels as constrained by trigonometric parallaxes and spectroscopicvalues of T eff and [Fe/H]. Finally, we list a set of 23interferometric binaries with masses known to be better than 3%, butwithout fundamental radius determinations (except ? Aur). Wediscuss the prospects for improving these and other stellar parametersin the near future.
| Absolute dimensions of eclipsing binaries. XXVII. V1130 Tauri: a metal-weak F-type system, perhaps with preference for Y = 0.23-0.24
Context. Double-lined, detached eclipsing binaries are our main sourcefor accurate stellar masses and radii. This paper is the first in aseries with focus on the upper half of the main-sequence band and testsof 1-2 M? evolutionary models. Aims: We aim todetermine absolute dimensions and abundances for the detached eclipsingbinary V1130 Tau, and to perform a detailed comparison with results fromrecent stellar evolutionary models. Methods: uvby light curvesand uvby? standard photometry have been obtained with theStrömgren Automatic Telescope, and high-resolution spectra havebeen acquired at the FEROS spectrograph; both are ESO, La Sillafacilities. We have applied the Wilson-Devinney model for thephotometric analysis, spectroscopic elements are based on radialvelocities measured via broadening functions, and [Fe/H] abundances havebeen determined from synthetic spectra and uvby calibrations. Results: V1130 Tau is a bright (mV = 6.56), nearby (71± 2 pc) detached system with a circular orbit (P = 0.80d). Thecomponents are deformed with filling factors above 0.9. Their masses andradii have been established to 0.6-0.7%. We derive a [Fe/H] abundance of-0.25 ± 0.10. The measured rotational velocities, 92.4 ±1.1 (primary) and 104.7 ± 2.7 (secondary) km s-1, arein fair agreement with synchronization. The larger 1.39M? secondary component has evolved to the middle of themain-sequence band and is slightly cooler than the 1.31M? primary. Yonsai-Yale, BaSTI, and Granada evolutionarymodels for the observed metal abundance and a “normal” Hecontent of Y = 0.25-0.26, marginally reproduce the components at agesbetween 1.8 and 2.1 Gyr. All such models are, however, systematicallyabout 200 K hotter than observed and predict ages for the more massivecomponent, which are systematically higher than for the less massivecomponent. These trends can not be removed by adjusting the amount ofcore overshoot or envelope convection level, or by including rotation inthe model calculations. They may be due to proximity effects in V1130Tau, but on the other hand, we find excellent agreement for 2.5-2.8 GyrGranada models with a slightly lower Y of 0.23-0.24. Conclusions:V1130 Tau is a valuable addition to the very few well-studied 1-2M? binaries with component(s) in the upper half of themain-sequence band, or beyond. The stars are not evolved enough toprovide new information on the dependence of core overshoot on mass (andabundance), but might - together with a larger sample of well-detachedsystems - be useful for further tuning of the helium enrichment law.Analyses of such systems are in progress.Based on observations carried out at the Strömgren AutomaticTelescope (SAT) and the 1.5 m telescope at ESO, La Silla (62.H-0319,62.L-0284, 63.H-0080, 64.L-0031, 66.D-0178). Table 11 is available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/510/A91
| Radii of Rapidly Rotating Stars, with Application to Transiting-Planet Hosts
The currently favored method for estimating radii and other parametersof transiting-planet host stars is to match theoretical models toobservations of the stellar mean density ?*, theeffective temperature T eff, and the composition parameter[Z]. This explicitly model-dependent approach is based on readilyavailable observations, and results in small formal errors. Itsperformance will be central to the reliability of results fromground-based transit surveys such as TrES, HAT, and SuperWASP, as wellas to the space-borne missions MOST, CoRoT, and Kepler. Here, I use twocalibration samples of stars (eclipsing binaries (EBs) and stars forwhich asteroseismic analyses are available) having well-determinedmasses and radii to estimate the accuracy and systematic errors inherentin the ?* method. When matching to the Yonsei-Yalestellar evolution models, I find the most important systematic errorresults from selection bias favoring rapidly rotating (hence probablymagnetically active) stars among the EB sample. If unaccounted for, thisbias leads to a mass-dependent underestimate of stellar radii by as muchas 4% for stars of 0.4 M sun, decreasing to zero for massesabove about 1.4 M sun. Relative errors in estimated stellarmasses are three times larger than those in radii. The asteroseismicsample suggests (albeit with significant uncertainty) that systematicerrors are small for slowly rotating, inactive stars. Systematic errorsarising from failings of the Yonsei-Yale models of inactive starsprobably exist, but are difficult to assess because of the small numberof well-characterized comparison stars having low mass and slowrotation. Poor information about [Z] is an important source of randomerror, and may be a minor source of systematic error as well. Withsuitable corrections for rotation, it is likely that systematic errorsin the ?* method can be comparable to or smaller than therandom errors, yielding radii that are accurate to about 2% for moststars.
| Absolute Dimensions of the G7+K7 Eclipsing Binary Star IM Virginis: Discrepancies with Stellar Evolution Models
We report extensive spectroscopic and differential photometric BVRIobservations of the active, detached, 1.309-day double-lined eclipsingbinary IM Vir, composed of a G7-type primary and a K7 secondary. Withthese observations, we derive accurate absolute masses and radii of M1 = 0.981 ± 0.012 M sun, M 2 =0.6644 ± 0.0048 M sun, R 1 = 1.061 ±0.016 R sun, and R 2 = 0.681 ± 0.013 Rsun for the primary and secondary, with relative errors under2%. The effective temperatures are 5570 ± 100 K and 4250 ±130 K, respectively. The significant difference in mass makes this afavorable case for comparison with stellar evolution theory. We findthat both stars are larger than the models predict, by 3.7% for theprimary and 7.5% for the secondary, as well as cooler than expected, by100 K and 150 K, respectively. These discrepancies are in line withpreviously reported differences in low-mass stars, and are believed tobe caused by chromospheric activity, which is not accounted for incurrent models. The effect is not confined to low-mass stars: therapidly rotating primary of IM Vir joins the growing list of objects ofnear-solar mass (but still with convective envelopes) that show similaranomalies. The comparison with the models suggests an age of 2.4 Gyr forthe system, and a metallicity of [Fe/H] ?-0.3 that isconsistent with other indications, but requires confirmation.
| Absolute Dimensions of the F-Type Eclipsing Binary Star VZ Cephei
We present new V-band differential photometry and radial velocitymeasurements of the unevolved, 1.18 day period, F+G-type, double-linedeclipsing binary VZ Cep. We determine accurate values for the absolutemasses, radii, and effective temperatures as follows: M A =1.402 ± 0.015 M sun, R A = 1.534 ±0.012 R sun, and T eff = 6690 ± 160 K forthe primary, and M B = 1.1077 ± 0.0083 Msun, R B = 1.042 ± 0.039 R sun,and T eff = 5720 ± 120 K for the secondary. Acomparison with current stellar evolution models suggests an age of 1.4Gyr for a metallicity that is near solar. The temperature differencebetween the stars, which is much better determined than the absolutevalues, is found to be ~ 250 K larger than predicted by theory. If allof this discrepancy is attributed to the secondary (which would then betoo cool compared to models), the effect would be consistent withsimilar differences found for other low-mass stars, generally believedto be associated with chromospheric activity. However, the radius of VZCep B (which unlike the primary, still has a thin convective envelope)appears normal, whereas in other stars affected by activity the radiusis systematically larger than predicted. Thus, VZ Cep poses a challengenot only to standard theory but also to our understanding of thediscrepancies in other low-mass systems.
| Absolute Properties of the Main-Sequence Eclipsing Binary Star GX Geminorum: Constraints on Convective Core Overshooting
We present 12,155 new differential photometric observations in the Vfilter made with the Undergraduate Research Studies in Astronomy andNF\Observatory WebScopes, as well as 33 radial velocities fromspectroscopic observations of the detached, 4.04 day double-linedeclipsing binary star GX Gem. Absolute dimensions of the components aredetermined from these new, and also from previously published, data withhigh precision (less than 0.7% in the masses and radii) for the purposeof testing various aspects of theoretical modeling. We obtain 1.488± 0.011 solar masses and 2.327 ± 0.012 solar radii for theprimary, and 1.467 ± 0.010 solar masses and 2.238 ± 0.012solar radii for the secondary. The effective temperatures andinterstellar reddening of the stars are accurately determined from thespectra, uvby?, and UBV photometry: 6195 ± 100 K for theprimary, 6165 ± 100 K for the secondary, corresponding tospectral types of F7 and F7 V, and 0.068 mag for the color excessEb - y . Spectral line widths give rotational velocities thatare synchronous with the mean orbital motion in a circular orbit. Thecomponents of GX Gem are relatively old main-sequence stars with an ageof about 2.8 billion years according to models. Because the componentsare located right at the end of their main-sequence evolutionary paths,we can place good limits on the convective core overshooting parameter.The lowest value of ?ov consistent with theobservations would appear to be approximately ?ov =0.18. Two different theories of tidal synchronization andcircularization agree that the components should be synchronouslyrotating, but disagree about whether or not the orbits should becircular.
| New Times of Minima of Some Eclipsing Variables
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.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| 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/.
| Sektion Lichtelektrische und CCD-Fotometrie 2002-2004.
Not Available
| The detached eclipsing binary system GX Geminorum.
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries
Not Available
| The detached eclipsing binary system GX Geminorum
Results of the photometric analysis by means of the Wilson-Devinneymethod, combined with an empirical mass-radius relation for LC IV starssupport the hypothesis that GX Gem is a well detached evolved system ofsubgiant stars. The solution is consistent with the known spectroscopicparameters obtained by Popper (1996) and the photometric data of Lacy(2002a).
| Times of Minima of Eclipsing Binaries
Not Available
| uvbyβ Photometry of Selected Eclipsing Binary Stars
New uvbyβ observations of 51 eclipsing binary stars are presented,and outside-eclipse averages for 45 of them are given. Many of thesebinaries are detached main-sequence pairs that have been discovered tobe double-lined spectroscopic binaries and appear suitable fordeterminations of accurate absolute dimensions and masses. Photometricproperties are recomputed for 14 of the binaries, for which absoluteproperties have been published previously. Intercomparisons are madewith previous photometry, when available, and notes are given for someindividual systems.
| Bericht vom Veranderlichen-Beobachter-Treffen im Mai in Hartha.
Not Available
| 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.
| Coordinates and Identifications for Sonneberg Variables on MVS 308-316
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries
Not Available
| A Spectroscopic Survey of Late F--K Eclipsing Binaries
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..106..133P&db_key=AST
| UBV photometry of selected eclipsing binary stars
The study reports new UBV observations of 69 eclipsing binary stars andprovides outside-eclipse averages. Revised photometric properties offive of the binaries, for which absolute properties were publishedpreviously, are computed. Comparisons are made with previous photometry,when available, and notes are given for some individual systems.
| UBVRI photometry of G, K, M HIPPARCOS stars
UBVRI data are presented for a set of 229 late-type stars, most of thembeing high proper motion stars. All these data are part of the InputCatalog planned observations for the Hipparcos mission.
| Program of Parallax Measurements from Space for the Nearest Eclipsing Binaries
Not Available
| The List of the Nearest and Bright Eclipsing Binaries from the HIPPARCOS Program
Not Available
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | תאומים |
| התרוממות ימנית: | 06h46m09.14s |
| סירוב: | +34°24'52.7" |
| גודל גלוי: | 11.718 |
| תנועה נכונה: | 5.9 |
| תנועה נכונה: | -18.7 |
| B-T magnitude: | 12.053 |
| V-T magnitude: | 11.746 |
קטלוגים וכינוים:
|
