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2006MNRAS.371.1793K -
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Mon. Not. R. Astron. Soc., 371, 1793-1812 (2006/October-1)
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Metallicity and absolute magnitude calibrations for UBV photometry.
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KARATAS Y. and SCHUSTER W.J.
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Abstract (from CDS):
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Calibrations are presented here for metallicity ([Fe/H]) in terms of the ultraviolet excess, [δ(*U* - *B*) at *B* - *V* = 0.6, hereafter δ_{0.6}], and also for the absolute visual magnitude (*M*_{V}) and its difference with respect to the Hyades (Δ*M*^{H}_{V}) in terms of δ_{0.6}and (*B* - *V*), making use of high-resolution spectroscopic abundances from the literature and *Hipparcos* parallaxes. The relation [Fe/H]-δ_{0.6}has been derived for dwarf plus turn-off stars, and also for dwarf, turn-off, plus subgiant stars classified using the *M*_{V}-(*B* - *V*)_{0}plane of Fig. 11, which is calibrated with isochrones from Bergbusch & VandenBerg (and also VandenBerg & Clem). The [Fe/H]-δ_{0.6}relations in our equations (5) and (6) agree well with those of Carney, as can be seen from Fig. 5(a). Within the uncertainties, the zero-points, +0.13(±0.05) of equation (5) and +0.13(±0.04) of equation (6), are in good agreement with the photometric ones of Cameron and of Carney, and close to the spectroscopic ones of Cayrel et al. and of Boesgaard & Friel for the Hyades open cluster. Good quantitative agreement between our estimated [Fe/H] abundances with those from *uvby*-β photometry and spectroscopic [Fe/H]_{spec}values demonstrates that our equation (6) can be used in deriving quality photometric metal abundances for field stars and clusters using *UBV* data from various photometric surveys.

For dwarf and turn-off stars, a new hybrid *M*_{V}calibration is presented, based on *Hipparcos* parallaxes with σ_{π}/π ≤ 0.1 and with a dispersion of ±0.24 in *M*_{V}. This hybrid *M*_{V}calibration contains δ_{0.6} and (*B* - *V*) terms, plus higher order cross-terms of these, and is valid for the ranges of +0.37 ≤ (*B* - *V*)_{0}≤ +0.88,- 0.10 ≤ δ_{0.6}≤ +0.29 and 3.44 ≤ *M*_{V}≤ 7.23. For dwarf and turn-off stars, the relation for Δ*M*^{H}_{V} is revised and updated in terms of (*B* - *V*) and δ_{0.6}, for the ranges of -0.10 ≤ δ_{0.6}≤ +0.29, and +0.49 ≤ (*B* - *V*)_{0}≤ +0.89, again making use of *Hipparcos* parallaxes with σ_{π}/π ≤ 0.1. These parallaxes for metal-poor dwarf and turn-off stars in our sample reveal that the difference of Δ*M*^{H}_*V*_(*B* - *V*) relative to Hyades at (*B* - *V*) = +0.70 should be 1.37mag, instead of the 1.58mag given by Laird et al. In general, *Hipparcos* parallaxes are larger than ground-based ones, causing a divergence of our Δ*M*^{H}_{V}(*B* - *V*,δ_{0.6}) relation (the solid line in Fig. 15b), from the one of Laird et al. (the dashed line) for the range +0.10 ≤ δ_{0.6}≤ +0.29; our absolute magnitudes are fainter, as has been confirmed for local subdwarfs by Reid. Our final calibrations for Δ*M*^{H}_{V}(*B* - *V*, δ_{0.6}), equations (16) and (17)), are third-order polynomials in δ_{0.6}, pass through the origin, and provide photometric distances in reasonable agreement with those obtained directly from *Hipparcos* parallaxes (Fig. 18).

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Abstract Copyright:
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2006 The Authors. Journal compilation © 2006 RAS

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Journal keyword(s):
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stars: abundances - stars: distances - solar neighbourhood
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VizieR on-line data:
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<Available at CDS (J/MNRAS/371/1793): table1.dat refs.dat>

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Simbad objects:
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533

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2019.09.16-04:58:04

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