Садржај
Слике
Уплоадјуј своје слике
DSS Images Other Images
Везани чланци
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.
| Flickering variability of T Coronae Borealis
We present electro-photometric UBV and high-speed U-band flickeringobservations of the recurrent nova T CrB during a period when its Ubrightness varies by more than 2 mag. The V band is dominated by theellipsoidal variability of the red giant; however, the variability ofthe hot component also causes ~0.15-mag variations in V. We define a setof parameters that characterize the flickering. The Fourier spectra ofall 27 nights are similar to each other. The power spectral density ofthe variations has a power-law component (~f-1.46 onaverage). We do not detect a dependence of the Fourier spectra andautocorrelation function on the brightness of the object. Havingsubtracted the contribution of the red giant, we show that theflickering amplitude correlates with the average flux of the accretingcomponent. A comparison with CH Cyg and MWC 560 indicates that theflickering of T CrB is more stable (at least during the time of ourobservations) than that in these jet-ejecting symbiotic stars. The dataare available in electronic form from the authors.
| 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
| Studies of the flickering in cataclysmic variables. V. The recurrent nova T Coronae Borealis
The flickering activity in the recurrent nova and symbiotic star T CrBis investigated using light curves taken in the Johnson U band. In orderto be able to compare the results with those of other CVs thecontribution of the red giant secondary is first estimated andsubtracted. It is found to be ~10% on the average. The U band fluxvaries considerably over long time scales, but the ratio of the flux ofthe flickering light source and the quiet part of the primary remainsconstant. This is in contrast to the behaviour of dwarf novae around theoutburst cycle. A wavelet analysis reveils a remarkable constancy of thedistribution of flickering energy among different time scales ascompared to other CVs. With the exception of the particular, not wellunderstood feature that the activity can disappear temporarily,flickering in T CrB is on the whole indistinguishable from that innormal cataclysmic variables, in particular in classical novae, althoughthe geometrical dimensions are very different. This is one moreindication that the vicinity of a white dwarf, being of similar size inall CVs independent of their absolute dimensions, is the site of theflickering.
| UBV Observations of T CrB
Not Available
| Activity of T Coronae Borealis in 1996
Not Available
| 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.
|
Додај нови чланак
Линкови у сродству са темом
Додај нови линк
Чланови следећих група \:
|
Посматрања и Астрометриски подаци
| Сазвежђа: | Змија |
| Ректацензија: | 15h56m24.77s |
| Deклинација: | +25°10'33.7" |
| Apparent магнитуда: | 8.418 |
| Даљина: | 105.042 parsecs |
| Proper motion RA: | -44 |
| Proper motion Dec: | 27.3 |
| B-T magnitude: | 9.032 |
| V-T magnitude: | 8.469 |
Каталог и designations:
|
