arXiv subjects

E. Masana

Publications and source records attributed to E. Masana.

41 records · Page 3Linked to original sources

arXiv2006

Effective temperature scale and bolometric corrections from 2MASS photometry

This paper presents a method to determine effective temperatures, angular semi-diameters and bolometric corrections for population I and II FGK type stars based on V and 2MASS IR photometry. Accurate calibration is accomplished by using a sample of solar analogues, whose average temperature is assumed to be equal to the solar effective temperature of 5777 K. By taking into account all possible sources of error we estimate associated uncertainties better than 1% in effective temperature and in the range 1.0-2.5% in angular semi-diameter for unreddened stars. Comparison of our new temperatures with other determinations extracted from the literature indicates, in general, remarkably good agreement. These results suggest that the effective temperaure scale of FGK stars is currently established with an accuracy better than 0.5%-1%. The application of the method to a sample of 10999 dwarfs in the Hipparcos catalogue allows us to define temperature and bolometric correction (K band) calibrations as a function of (V-K), [m/H] and log g. Bolometric corrections in the V and K bands as a function of effective temperature, [m/H] and log g are also given. We provide effective temperatures, angular semi-diameters, radii and bolometric corrections in the V and K bands for the 10999 FGK stars in our sample with the corresponding uncertainties.

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arXiv2004

uvby-Hbeta CCD Photometry of NGC 1817 and NGC 1807

We have investigated the area of two NGC entries, NGC 1817 and NGC 1807, with deep CCD photometry in the uvby-Hbeta intermediate-band system. The photometric analysis of a selected sample of stars of the open cluster NGC 1817 yields a reddening value of E(b-y)= 0.19$\pm$0.05, a distance modulus of V0-MV= 10.9$\pm$0.6, a metallicity of [Fe/H]= -0.34$\pm$0.26 and an age of log t = 9.05$\pm$0.05. Our measurements allow us to confirm that NGC 1807 is not a physical cluster.

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arXiv2003

Effective temperatures and radii of planet-hosting stars from IR photometry

In this paper we present and analyse determinations of effective temperatures of planet-hosting stars using infrared (IR) photometry. One of our goals is the comparison with spectroscopic temperatures to evaluate the presence of systematic effects that could alter the determination of metal abundances. To estimate the stellar temperatures we have followed a new approach based on fitting the observed 2MASS IR photometry with accurately calibrated synthetic photometry. Special care has been put in evaluating all sources of possible errors and incorporating them in the analysis. A comparison of our temperature determinations with spectroscopic temperatures published by different groups reveals the presence of no systematic trends and a scatter compatible with the quoted uncertainties of 0.5-1.3%. This mutual agreement strengthens the results of both the spectroscopic and IR photometry analyses. Comparisons with other photometric temperature calibrations, generally with poorer performances, are also presented. In addition, the method employed of fitting IR photometry naturally yields determinations of the stellar semi-angular diameters, which, when combined with the distances, results in estimations of the stellar radii with remarkable accuracies of ~2-4%. A comparison with the only star in the sample with an empirically determined radius (HD 209458 -- from transit photometry) indicates excellent agreement.

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arXiv2000

The luminosity calibration of the uvby-$β$ photometry

The ESA HIPPARCOS satellite has provided astrometry of unprecedented accuracy, allowing to reassess, improve and refine the pre-HIPPARCOS luminosity calibrations. We review the "classical" absolute magnitude calibrations with the Stroemgren-Crawford intermediate-band photometric system. A small zero point correction of about 2-4% seems necessary, as well as to refine the dependences on metallicity and projected rotational velocity. The need of a rigorous statistical treatment of the extremely precise HIPPARCOS to derive definite dependences of the luminosity on physical stellar parameters is emphasized.

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arXiv1998

CP stars: Photometric calibrations of luminosity using Hipparcos data

The application of the Stromgren photometric luminosity calibrations to different types of CP stars is reexamined in the light of the new Hipparcos data. A first attempt is made to use the LM statistical parallax method (Luri et al., 1996) -- based on the maximum likelihood principle -- to obtain a calibration of the absolute magnitude as a function of two Stromgren colour indices, thus reflecting effective temperature and evolution. Its application to a sample of Si stars and to a sample of normal main sequence stars in the same spectral range allows us to compare the calibrations obtained and to discuss the position of Si stars in the HR diagram. Additionally, a sample of bonafide, spectroscopically selected Am stars together with normal main sequence stars are used to derive a new absolute magnitude calibration for late A-type main sequence stars, taking into account the effects of evolution, metallicity and stellar rotation.

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