Contenidos
Imágenes
Subir su imagen
DSS Images Other Images
Artículos relacionados
Rotational Brightness Modulation and Starspots on the RS CVn-type Stars IN Com, IL Com, UX Ari, and V711 Tau
UBVRI photometric observations and models of spotting are presented forfour noneclipsing RS CVn systems: IN Com (G5III/IV), IL Com (F8V+F8V),UX Ari (K01V+G5V), and V711 Tau (K1IV+G5V). A low amplitude variabilitycaused by cold (T=1700K)spots which can occupy up to 19% of the star''ssurface is confirmed for the little-studied star IL Com. Long-term lightcurves are constructed and the stellar magnitudes and color indices ofthe unspotted photospheres are estimated for IN com, UX Ari, and V711Tau. It is shown that UX Ari becomes bluer with decreasing brightness,so its variability cannot be fully explained in terms of cold spots.Models of spotting on In Com and V711 Tau are constructed from the fullset of available photometric observations. The spots on both of thesevariables lie at middle latitudes and occupy up to 22% (In Com) and 33%(V711 Tau) of the stars'' surfaces. Both stars manifest a tendency forthe width of the spots to decrease as their area increases. This is acrude analog of the Maunder butterflies. These stars experience cyclicalspot activity and have a differential rotation of the type found on thesun.
| Simultaneous optical and X-ray observations of flares and rotational modulation on the RS CVn binary HR 1099 (V711 Tau) from the MUSICOS 1998 campaign
We present simultaneous and continuous observations of the Hα,Hβ, He I D3, Na I D1, D2 doubletand the Ca II H & K lines for the RS CVn system HR 1099. Thespectroscopic observations were obtained during the MUSICOS 1998campaign involving several observatories and instruments, both echelleand long-slit spectrographs. During this campaign, HR 1099 was observedalmost continuously for more than 8 orbits of 2.8 deg. Two large opticalflares were observed, both showing an increase in the emission ofHα, Ca II H & K, Hβ and He I D3 and a strongfilling-in of the Na I D1, D2 doublet.Contemporary photometric observations were carried out with the robotictelescopes APT-80 of Catania and Phoenix-25 of Fairborn Observatories.Maps of the distribution of the spotted regions on the photosphere ofthe binary components were derived using the Maximum Entropy andTikhonov photometric regularization criteria. Rotational modulation wasobserved in Hα and He I D3 in anti-correlation with thephotometric light curves. Both flares occurred at the same binary phase(0.85), suggesting that these events took place in the same activeregion. Simultaneous X-ray observations, performed by ASM on board RXTE,show several flare-like events, some of which correlate well with theobserved optical flares. Rotational modulation in the X-ray light curvehas been detected with minimum flux when the less active G5 V star wasin front. A possible periodicity in the X-ray flare-like events was alsofound.Based on observations obtained during the MUSICOS 98 MUlti-SIteCOntinuous Spectroscopic campaign from Observatoire de Haute-Provence,France, Kitt Peak National Observatory, USA, ESO La Silla, Chile, Mt.Stromlo Observatory, Australia, Xinglong National Observatory, China,Isaac Newton Telescope, Spain, Laboratório Nacional deAstrofísica, Brazil, and South African Astronomical Observatory,South Africa. Contemporaneous observations from Catania, Italy andFairborn Observatories, USA, and on data obtained with the Rossi X-rayTiming Explorer.
| Measuring starspot temperature from line depth ratios. I. The method
Gray and collaborators have recently demonstrated that line-depth ratiosare a powerful tool for temperature discrimination, able to resolvedifferences <=10 K. The method has been applied to detect temperaturevariations in the 5-15 K range due to activity cycles (e.g. Gray et al.\cite{Gray96a}, \cite{Gray96b}) or to rotation modulation produced bylarge surface features, called ``star-patches", like that detected in xiBoo A by Toner & Gray (\cite{Toner88}). Cool starspots of a fewtenths of the stellar surface produce bumps in a line profile, whichmigrate through the line profile allowing Doppler-imaging in fastrotating stars. In the hypothesis that in slowly-rotating stars thepassage of dark spots produces modulation of the center line depth ofdifferent amount in lines of different sensitivity to temperature, wehave made test observations on three active binaries of the RS CVn type.Based on observations made at the Catania Astrophysical Observatory at aresolution R = 14 000, we show that line-depth ratios can be effectivelyused to determine spot temperatures of active binary systems. Using, onaverage, ten line pairs, selected in the 6100-6300 Å wavelengthrange, with the help of observations of 30 main sequence and giantstars, we have derived a calibration relation of line-depth ratios (LDR)in an absolute temperature scale, taking into account the gravity effectin the calibration relation. Single LDRs converted to temperaturethrough the calibration relations have led to clear rotationalmodulation of the average surface temperature with amplitudes of 177 K,119 K, and 127 K for VY Ari, IM Peg and HK Lac, with average estimatederrors of about 10 K. We show that the observed temperature variationamplitude allows us to define a minimum fractional spotted area coverageas a function of spot-photosphere temperature ratio. Adopting themaximum value of average temperature, determined from the LDRs, as thatof the unspotted photosphere, we computed the average spot temperaturecorresponding to the minimum spot coverage. Although not univocallyconstrained, the temperature difference (Delta T =Tph-Tsp) obtained for the three systems, Delta T =890 K for VY Ari, Delta T = 750 K for IM Peg, and Delta T = 810 K for HKLac, are in good agreement with values derived with other methods. Basedon observations collected at Catania Astrophysical Observatory, Italy.}
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| Starspot photometry with robotic telescopes. UBV(RI)_C and by light curves of 47 active stars in 1996/97
We present continuous multicolor photometry for 47 stars from October1996 through June 1997. Altogether, 7073 V(RI)_c, UBV, and by datapoints, each the average of three individual readings, were acquiredwith three automatic photoelectric telescopes (APTs) at FairbornObservatory in southern Arizona. Most of our targets arechromospherically active single and binary stars of spectral type G to Kbut there are also four pre-main-sequence objects and three pulsatingstars in our sample. The light variability is generally due torotational modulation of an asymmetrically spotted stellar surface andtherefore precise rotational periods and their seasonal variations aredetermined from Fourier analysis. We also report on photometricvariations of gamma CrB (A0V) with a period of 0.44534 days. All dataare available in numerical form. All data are available from CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Absolute declinations with the photoelectric astrolabe at Calern Observatory (OCA)
A regular observational programme with a photoelectric astrolabe havebeen performed at ``Observatoire du Calern" (Observatoire de laCôte d'Azur, OCA, phi = +43() o44′55.011″; lambda =-0() h27() m42.44() s, Calern, Caussols, France) for the last twentyyears. It has been almost fully automatized between 1984 and 1987. Since1988 the photoelectric astrolabe was used without any modification. Inaddition to determining the daily orientation of the local vertical, theyearly analysis of the residuals permits to derive corrections to theused star catalogue \cite[(Vigouroux et al. 1992)]{vig92}. A globalreduction method was applied for the ASPHO observations. The new form ofthe equations \cite[(Martin & Leister 1997)]{mar97} give us thepossibility of using the entire set of the observing program using datataken at two zenith distances (30() o and 45() o). The program containsabout 41648 stars' transits of 269 different stars taken at``Observatoire du Calern" (OCA). The reduction was based on theHIPPARCOS system. We discuss the possibility of computing absolutedeclinations through stars belonging simultaneously to the 30() o and45() o zenith distances programmes. The absolute declination correctionswere determined for 185 stars with precision of 0.027arcsec and thevalue of the determined equator correction is -0.018arcsec +/-0.005arcsec . The instrumental effects were also determined. The meanepoch is 1995.29. Catalogue only available at CDS in electronic from viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Catalogs of temperatures and [Fe/H] averages for evolved G and K stars
A catalog of mean values of [Fe/H] for evolved G and K stars isdescribed. The zero point for the catalog entries has been establishedby using differential analyses. Literature sources for those entries areincluded in the catalog. The mean values are given with rms errors andnumbers of degrees of freedom, and a simple example of the use of thesestatistical data is given. For a number of the stars with entries in thecatalog, temperatures have been determined. A separate catalogcontaining those data is briefly described. Catalog only available atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Goddard High Resolution Spectrograph Observations of Variability in the RS Canum Venaticorum System V711 Tauri (HR 1099)
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...470.1172D&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.
| H alpha survey of late-type active binaries
H alpha spectrophotometry of 33, chromospherically active, closebinaries (mostly RS CVn), obtained at the Catania AstrophysicalObservatory, is reported. We define the H alpha emission component foreach observed system as the difference between the observed spectrum anda synthetic 'composite' spectrum made up by the weighted sum of spectraof non active stars similar in spectral types to the components of thesystem. This procedure allows us to detect an emission component in theH alpha core, also for some systems which apparently present a normal Halpha absorption profile. We investigate the possible correlationbetween this net H alpha surface flux and luminosity as a function of(B-V) and the rotational period. In particular we find that the net Halpha surface flux correlates moderately well with the rotationalperiod, in agreement with previous results. The trend of increasingactivity with decreasing rotational period can be described either by apower law or an exponential law.
| Improved Mean Positions and Proper Motions for the 995 FK4 Sup Stars not Included in the FK5 Extension
Not Available
| Evolved GK stars near the sun. I - The old disk population
A sample of nearly two thousand GK giants with intermediate band, (R,I),DDO and Geneva photometry has been assembled. Astrometric data is alsoavailable for most of the stars. The some 800 members of the old diskpopulation in the sample yield accurate luminosities (from two sources),reddening values and chemical abundances from calibrations of thephotometric parameters. Less than one percent of the objects arepeculiar in the sense that the flux distribution is abnormal. Thepeculiarity is signaled by strong CH (and Ba II) and weak CH. The CH+stars are all spectroscopic binaries, probably with white dwarfcompanions, whereas the CH- stars are not. A broad absorption band,centered near 3500 A, is found in the CH+ stars whereas the CH- objectshave a broad emission feature in the same region. The intensity of theseabsorptions and emissions are independent of the intensity of abnormalspectral features. Ten percent of the old disk sample have a heavyelement abundance from one and a half to three times the solar value.The distribution of the heavy element abundances is nearly a normal onewith a peak near solar abundance and ranges three times to one sixthsolar. The distribution of the (U, V) velocities is independent of theheavy element abundance and does not appear to be random. Ten percent ofthe old disk stars show a CN anomaly, equally divided between CN strongand CN weak. Several stars of individual astrometric or astrophysicalimportance are isolated.
| Long-term monitoring of active stars. II - UBV(RI)c observations at ESO during January-March 1989
In the framework of a research program focusing on the global propertiesand evolution of photospheres and outer atmospheres of active stars, theauthor presents high-precision UBV(RI)c photometry of 15 selected RSCVn, BY Dra, and FK Com-type systems observed at the European SouthernObservatory (La Silla, Chile) in the period January-March 1989.Significant evolution both in amplitude and shape of the wave-like lightcurves is found with respect to previous observations. Evidence forlong-term variability for most of the observed stars is also presented,and some of the spectral classifications are rediscussed.
| Long-term monitoring of active stars. I - 1988-89 UBV photometry with the PHOENIX APT
As part of a large program aimed at studying the global properties andevolution of active star atmospheres, high-precision UBV photometry ofselected RS CVn, BY Dra, and FK Com-type systems has been carried outsince early 1988 by using the Phoenix 25-cm Automatic PhotoelectricTelescope at Whipple Observatory on Mt. Hopking (USA, AZ). We presentthe results of systematic obsrvations of nine active stars monitoredduring the years 1988 and 1989. Significant evolution of the wave-likelight curves for most of the observed stars, both in amplitude andshape, is found. These photometric data can give important clues on thelifetimes of spotted areas and associated magnetic structures,differential rotation and solar-like cycles, and are required to addressthe question of spatial and physical correlations between confinedstructures in active star photospheres and outer atmospheres, the latterderived from chromospheric and transition region spectral signatures atother wavelengths. Evidence of long-term variability for most of theobserved stars is also presented.
| A critical appraisal of published values of (Fe/H) for K II-IV stars
'Primary' (Fe/H) averages are presented for 373 evolved K stars ofluminosity classes II-IV and (Fe/H) values beween -0.9 and +0.21 dex.The data define a 'consensus' zero point with a precision of + or -0.018 dex and have rms errors per datum which are typically 0.08-0.16dex. The primary data base makes recalibration possible for the large(Fe/H) catalogs of Hansen and Kjaergaard (1971) and Brown et al. (1989).A set of (Fe/H) standard stars and a new DDO calibration are given whichhave rms of 0.07 dex or less for the standard star data. For normal Kgiants, CN-based values of (Fe/H) turn out to be more precise than manyhigh-dispersion results. Some zero-point errors in the latter are alsofound and new examples of continuum-placement problems appear. Thushigh-dispersion results are not invariably superior to photometricmetallicities. A review of high-dispersion and related work onsupermetallicity in K III-IV star is also given.
| High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances
A high-resolution spectroscopic survey of 671 G and K field giants isdescribed. Broad-band Johnson colors have been calibrated againstrecent, accurate effective temperature, T(eff), measurements for starsin the range 3900-6000 K. A table of polynomial coefficients for 10color-T(eff) relations is presented. Stellar atmosphere parameters,including T(eff), log g, Fe/H, and microturbulent velocity, are computedfor each star, using the high-resolution spectra and various publishedphotometric catalogs. For each star, elemental abundances for a varietyof species have been computed using a LTE spectrum synthesis program andthe adopted atmosphere parameters.
| UBVRI observations of southern hemisphere active stars
A program of high-precision UBVRI photometry of selected southernhemisphere active stars has been carried out at the European SouthernObservatory (La Silla, Chile) from November 1985 to February 1987. Oneresult of such monitoring has been the acquisition of the complete orpartially complete light curves for 11 stars. Significant changes oftheir wavelike light curves, both in amplitude and shape, are found.These observations are important to produce a homogeneous and extendeddatabase, which is necessary to track the formation and evolution ofphotospheric active regions.
| Large and kinematically unbiased samples of G- and K-type stars. IV - Evolved stars of the old disk population
Modified Stromgren and (R,I) photometry, along with DDO and Genevaphotometry, are presented for a complete sample of evolved old-disk Gand K giants in the Bright Star Catalogue. Stars with ages of between1.5 x 10 to the 9th and 10 to the 10th yr are found to have anear-normal distribution of heavy element abundances, centered on anFe/H abundance ratio of -0.1 dex. The old disk clusters NGC 3680 and IC4651 contain red-straggler young-disk giants that are probablycontemporaries of the blue stragglers in the clusters.
| Large and kinematically unbiased samples of G- and K-type stars. II - Observations of evolved stars in the Bright Star sample. III - Evolved young disk stars in the Bright Star sample
Four color and RI observations were obtained for a large sample ofG-type and K-type stars in the Bright Star Catalogue. Data are firstpresented for 110 evolved stars. Photometry of evolved young diskpopulation stars have then been calibrated for luminosity, reddening,and metallicity on the basis of results for members of the Hyades andSirius superclusters. New DDO results are given for 120 stars.
| A search for lithium-rich giant stars
Lithium abundances or upper limits have been determined for 644 brightG-K giant stars selected from the DDO photometric catalog. Two of thesegiants possess surface lithium abundances approaching the 'cosmic' valueof the interstellar medium and young main-sequence stars, and eight moregiants have Li contents far in excess of standard predictions. At leastsome of these Li-rich giants are shown to be evolved to the stage ofhaving convectively mixed envelopes, either from the direct evidence oflow surface carbon isotope ratios, or from the indirect evidence oftheir H-R diagram positions. Suggestions are given for the uniqueconditions that might have allowed these stars to produce or accrete newlithium for their surface layers, or simply to preserve from destructiontheir initial lithium contents. The lithium abundance of the remainingstars demonstrates that giants only very rarely meet the expectations ofstandard first dredge-up theories; the average extra Li destructionrequired is about 1.5 dex. The evolutionary states of these giants andtheir average masses are discussed briefly, and the Li distribution ofthe giants is compared to predictions of Galactic chemical evolution.
| Rotational modulation and flares on RS CVn and BY DRA stars
Evidence is presented for spots, plages, and flares on the noneclipsingRS CVn system II Peg and V 711 Tau. The large spot originally found onII Peg in 1981.8 could still be identified in 1983. Two spectroscopicflares of II Peg were detected. For the larger flare the fluxes in thestrongest transition-region lines reached about six times theirquiescent values. A comparison of the 1981 and 1983 flux variations showthat active regions or plages are located on one hemisphere. On V 711Tau at least two flares were observed. Outside of these flares, thestrongest chromospheric and transition-region emission lines exhibitedweak phase-dependent variations that persist over 173 orbital cycles(1981-1983) and are possibly associated with one of the proposed spots.For both stellar systems the fluxes from the higher temperature emissionlines showed the greatest variations.
| E. W. Fick Observatory stellar radial velocity measurements. I - 1976-1984
Stellar radial velocity observations made with the large vacuumhigh-dispersion photoelectric radial velocity spectrometer at FickObservatory are reported. This includes nearly 2000 late-type starsobserved during 585 nights. Gradual modifications to this instrumentover its first eight years of operation have reduced the observationalerror for high-quality dip observations to + or - 0.8 km/s.
| Coordinated Ultraviolet, Optical and Radio Observations of RS CVn and Flare Stars
Not Available
| Uvby-Beta Photometry of Equatorial and Southern Bright Stars - Part Two
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...42..311H&db_key=AST
| Photoelectric Observations of V711 Tauri
Not Available
| 1977-1978 photometry of V711 Tau=HR 1099 - Before the radio outburst
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978AJ.....83.1510B&db_key=AST
| Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson Observatory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
| UBV photometry of 550 F, G and K type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966MNRAS.133..475A&db_key=AST
|
Enviar un nuevo artículo
Enlaces relacionados
- - No se han encontrado enlaces -
En viar un nuevo enlace
Miembro de los siguientes grupos:
|
Datos observacionales y astrométricos
| Constelación: | Tauro |
| Ascensión Recta: | 03h39m51.10s |
| Declinación: | +03°03'25.0" |
| Magnitud Aparente: | 5.57 |
| Distancia: | 122.85 parsecs |
| Movimiento Propio en Ascensión Recta: | -36.8 |
| Movimiento Propio en Declinación: | 8.2 |
| B-T magnitude: | 6.719 |
| V-T magnitude: | 5.658 |
Catálogos y designaciones:
|
INHABITED SKY
