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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.
| Candidate Pre-Main-Sequence F Stars with Circumstellar Dust Identified Using Combined 2MASS and uvby Data
We propose a method that uses near-infrared plus uvby photometry toidentify potentially extensive circumstellar dusty environments around Fand A stars. The method has been applied to a sample of ~900 metal-richreddened F stars with 2 Micron All Sky Survey and uvby data, suggestingthe presence of circumstellar dust emitting in the near-infrared for ~70stars. The logTe-MV diagram suggests that most, ifnot all, are likely pre-main-sequence (PMS) stars. They seem to be acontinuation of the class of Herbig Ae/Be PMS stars in the spectral typeF. Their number drops sharply downward of logTe~3.84(spectral types later than ~F5), which may provide new clues to the PMSevolution of 1-2 Msolar stars. We present a list of 21 of themost conspicuous candidate stars with circumstellar dust. About half ofthem are associated with the extended star-forming region around ρOphiuchi. The brightest of these 21 stars, with V<~7.5, turn out tobe IRAS sources, suggesting the presence of heated dust emitting in thefar-infrared. Also in this list, HD 81270 is reported as a very unusualstar moving away from the Galactic plane at a projected speed of 70 kms-1.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| Estimation of spectral classifications for bright southern stars with interesting Stromgren indices
This paper investigates the degree of success with which uvby photometrycan be applied to predict spectral classifications for 947 A, F, and Gstars brighter than an apparent magnitude of 8.3 and with four-colorindices indicating some kind of interesting, unusual, or peculiarspectrum. One or several possible spectral classifications are estimatedfor each star from photometry alone, double stars are distinguished, andthe estimates are compared with published classifications. The resultsshow that the framework provided by uvby photometry can be extended toinclude most G and K stars, reddened stars, peculiar stars, and certaintypes of double star.
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | נושא הנחש |
| התרוממות ימנית: | 16h54m50.01s |
| סירוב: | -26°24'47.1" |
| גודל גלוי: | 8.213 |
| מרחק: | 229.358 פארסק |
| תנועה נכונה: | -14.5 |
| תנועה נכונה: | -7.9 |
| B-T magnitude: | 8.66 |
| V-T magnitude: | 8.25 |
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