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מאמרים קשורים
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.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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
| Observations of Galaxies with the Midcourse Space Experiment
We have imaged eight nearby spiral galaxies with the SPIRIT III infraredtelescope on the Midcourse Space Experiment (MSX) satellite in themid-infrared at 18" resolution at 8.3, 12.1, 14.7, and 21.3 μm. Eachof the eight shows interesting structure not previously detected witholder, lower resolution infrared data sets, such as a resolved nucleusor spiral structure. The MSX data are compared with existing data setsat ultraviolet, optical, and infrared wavelengths, including recentobservations from the Infrared Space Observatory. The infraredstructures in M83 and NGC 5055 show a striking similarity to theultraviolet emission but are less similar to the optical emission.Several point sources with no identified counterparts at otherwavelengths are found near M31, NGC 4945, M83, and M101. Over 200previously known objects are also detected at 8 μm.
| 8-13 μm spectroscopy of NGC 253: a spatially resolved starburst
NGC 253 is a nearby spiral galaxy that is currently undergoing a nuclearburst of star formation in a 100 pc diameter region. We presentspatially resolved 8-13 μm low-resolution spectra at four positionsalong the ridge of 8-13 μm emission. We find that the relativestrengths of the ionic and dust emission features, and dust continuumemission vary with position in the galaxy, but can be accounted foreverywhere without recourse to extinction by silicates. The brightestmid-infrared peak (which is displaced from the nucleus) has elevatedlevels of both continuum and 11.1-12.9 μm `plateau' emission,indicative of dust heated within a photodissociation region. Spectraobtained over the course of 3 yr at the position of the brightestmid-infrared peak show no significant time variation.
| The 3.28 micron emission feature in NGC 253
The 3.28 micrometer polycyclic aromatic hydrocarbon (PAH) emissionfeature in the galaxy NGC 253 comes from an extended star formationregion approximately 100 pc across. The brightest mid-infrared source inthe galaxy, which is displaced approximately 45 pc from the probablenucleus, does not show the PAH feature; it may be a dust-enshroudedrecent supernova.
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| Near-infrared observations of NGC 253
Isophotes of the surface brightness of NGC 253 were obtained at 0.7-0.9,1.25, and 2.2 microns by means of the photographic and photoelectricmethods. The observed color, (0.8 micron)-(2.2 microns), of the diskranges from 2.0 to 2.8 mag, corresponding to the colors of M0 III and M4III stars, respectively. The significant difference of colors betweenthe near and far sides is indicative of the local distribution of dustand stars associated with the galactic arm. The visual extinction in the4-kpc arm is estimated to be 0.5 mag at face-on value. In the centralregion, the observed color, (0.8 micron)-(2.2 microns), amounts to 3.0mag for a 22-arcsec beam due to a strong reddening effect. The amount ofdust within 210 pc from the center is found to produce A(V) = 5-6 mag,equivalent to 10,000-12,000 solar mass. Dust-to-gas ratios are alsoobtained in the disk and bulge of NGC 253 and found to be a littlesmaller than that in the disk of the Galaxy.
| On apparent associations among astronomical objects
An apparent association among bright stars and bright galaxies has beenfound that has a maximum a posteriori probability for chance occurrenceof about 0.008. The ability to find such an association is evidence thatapparent associations among objects of different redshifts should beviewed with great caution.
| Ultrashort-Period Variables and the Masses of Blue Stragglers in the Old Disk Population
Abstract image available at:http://adsabs.harvard.edu/abs/1970PASP...82..274E
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | פסל |
| התרוממות ימנית: | 00h47m34.81s |
| סירוב: | -25°23'41.9" |
| גודל גלוי: | 8.874 |
| מרחק: | 118.203 פארסק |
| תנועה נכונה: | -13.8 |
| תנועה נכונה: | -1.7 |
| B-T magnitude: | 9.561 |
| V-T magnitude: | 8.931 |
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