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Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| A Theoretical γ Doradus Instability Strip
In this paper, we present the first theoretical γ Doradusinstability strip. We find that our model instability strip agrees verywell with the previously established, observationally based, instabilitystrip of Handler & Shobbrook. We stress, as do Guzik et al., thatthe convection zone depth plays the major role in the determination ofour instability strip. Once this depth becomes too deep or too shallow,the convection zone no longer allows for pulsational instability. Ourtheoretical γ Dor instability strip is bounded by ~6850 and 7360 Kat the red and blue edge, respectively, on the zero-age main sequenceand by ~6560 and 7000 K at the red and blue edge, respectively,approximately 2 mag more luminous. This theoretical strip, transformedto the observer's color-magnitude diagram, overlays the region wheremost of the 30 bona fide γ Dor stars are found.
| A Dozen New γ Doradus Stars
We use new high-dispersion spectroscopic and precise photometricobservations to identify 12 new γ Doradus stars. Two of the 12systems are double-lined binaries that show obvious velocityvariability. Five other stars have metallic lines with compositeprofiles characterized by a narrow feature near the center of each broadcomponent. Spectrograms of the Hα line indicate that all fivestars are binaries rather than shell stars. The remaining five stars inour sample are probably single. All 12 stars are photometricallyvariable with amplitudes between 6 and 87 mmag in Johnson B and periodsbetween 0.3 and 1.2 days. Four stars are monoperiodic; the rest havebetween two and five independent periods. The variability at all periodsapproximates a sinusoid. Although many of the stars lie within theδ Scuti instability strip, none exhibit the higher frequencyvariability seen in δ Scuti stars. We have increased the sample ofknown γ Doradus stars by 40% and revised the positions of a numberof variables in the H-R diagram by accounting for duplicity. Our list of42 confirmed γ Doradus variables gives some of their properties.All are dwarfs or subgiants and lie within a well-defined region of theH-R diagram that overlaps the cool edge of the δ Scuti instabilitystrip. We compare the observed location of the γ Doradus variableswith a recently published theoretical γ Doradus instability stripand find good agreement.
| Six New γ Doradus Stars
We present high-resolution spectroscopy and precision photometry of sixnew γ Doradus stars, one of which was independently discovered byanother group. This brings the total number of confirmed γ Doradusvariables to 30. All six of these variables fall in the spectral classrange F0-F2 all but one are subgiants. The six stars have between oneand five photometric periods in the range 0.3-1.2 days. We find noevidence for higher frequency δ Scuti pulsations in any of thesesix stars. Our spectroscopic observations reveal HD 108100 to be thefirst confirmed γ Doradus variable with composite broad and narrowline profiles suggesting the presence of a circumstellar shell or disk.HD 221866 has the most asymmetric absorption lines of the six stars inthis paper and also the largest photometric amplitude. Most of the 30confirmed γ Doradus variables lie in a fairly tight region of theH-R diagram on or just above the main sequence that partially overlapsthe cool edge of the δ Scuti instability strip. However, threestars, including two of the new variables in this paper, are subgiantsthat lie well within the δ Scuti strip. Among the 30 confirmedγ Doradus variables, we find no correlation between thephotometric periods and intrinsic color, absolute magnitude, orluminosity.
| 10 New γ Doradus and δ Scuti Stars
We present high-resolution spectroscopy and precision photometry of fivenew γ Doradus and five new δ Scuti variables. The five newγ Doradus variables substantially increase the number of confirmedstars of this class. All 10 stars fall in the spectral class rangeF0-F2, but they are cleanly separated into two groups by theirluminosity and photometric periods. However, the period gap between theγ Doradus and δ Scuti stars is becoming very narrow since weconfirm that HD 155154 is a γ Doradus star with the shortestperiods reported to date (the shortest of its four periods is ~0.312days). We do not find any evidence in our sample for stars exhibitingboth δ Scuti- and γ Doradus-type pulsations.
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| The Photometric Variability of Sun-like Stars: Observations and Results, 1984--1995
Using differential Stromgren b, y photometry, we monitored thebrightness variations of 41 program stars and their 73 comparison starsfrom 1984 through 1995. The predominantly main-sequence program starsspanned ranges of temperature and mean chromospheric activity centeredon solar values. About 40% of all the stars showed measurablevariability, typically at levels below 0.01 mag (~1%), on bothnight-to-night and year-to-year timescales. The variability correlatedwith mean chromospheric activity and advancing spectral type. We presentdifferential light curves and statistical descriptions of ourobservations.
| Photometry of Stars in the Field of ZZ Draconis
Not Available
| Photometry for Stars in the Field of V Bootis
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.
| Common proper motion stars in the AGK 3
A search was made of common-proper-motion (CPM) systems among AGK 3stars. The selection of physical systems was based upon the ratiobetween the angular separation (rho) and the proper motion (mu); the CPMstars found are presented in two tables. Table I lists systems withrho/mu less than 1000 years. It contains 326 entries, and the proportionof optical pairs is estimated to be 1 percent. Table II lists systemswith rho/mu in the range 1000 to 3500 years; it contains 113 systems,but only 60 percent of them are physical. Nevertheless, these systemsoften have separations larger than 10,000 AU and are the mostinteresting for the study of the tail of the distribution function ofthe semimajor axes.
| An investigation of the consistency of the calibrations of the UVBY beta and GNKMF photometric systems.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971A&A....15..161O&db_key=AST
| Magnitudes and colors for 833 Northern and Southern stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955AJ.....60...65E&db_key=AST
| On the cause underlying the spectral differences of the stars.
Not Available
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Pozíciós és asztrometriai adatok
| Csillagkép: | Kígyótartó |
| Rektaszcenzió: | 17h39m04.54s |
| Deklináció: | +02°03'15.0" |
| Vizuális fényesség: | 7.741 |
| Távolság: | 109.769 parszek |
| RA sajátmozgás: | 45.1 |
| Dec sajátmozgás: | -23.2 |
| B-T magnitude: | 8.2 |
| V-T magnitude: | 7.779 |
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