A. Arellano Ferro
Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70–264, México D.F. 04510, México (armando@astro.unam.mx).
Received 2010 May 25
Accepted 2010 July 2
RESUMEN
]]> A partir de datos fotoeléctricos en el sistema uvby — β y de valores precisos sintéticos y espectroscópicos de T eff y log g en 50 supergigantes de tipos espectrales F–G, hemos calculado relaciones funcionales que permiten la estimación inicial de la temperatura efectiva y la gravedad en este tipo de estrellas. Se demuestra que aunque las calibraciones de Teff fueron calculadas con los datos de estrellas supergigantes jóvenes y masivas, también son válidas para estrellas evolucionadas post–AGB y RV Tau de temperaturas similares. La gravedad superficial también puede calcularse a partir del índice Δ[c1] con una precisión de 0.26 dex. Aunque se puede distinguir una correlación entre MV y Δ[c1], no hemos encontrado una correlación que prediga MV de manera suficientemente precisa.
ABSTRACT
From photoelectric uvby — β data and recent accurate synthetic and spectroscopic values of Teff and log g for 50 F–G supergiants, we have calculated functional relationships that lead to initial estimates of effective temperature and gravities for these types of stars. It is shown that while the Teff relationships are calculated using the data on young massive supergiants, they are also valid for evolved stars of similar temperatures like post–AGB and RV Tau stars. The gravity can also be predicted from the Δ[c1]index with an uncertainty of about 0.26 dex. Although a clear and significant trend between MV and Δ[c1] is seen, no calibration is found that predicts accurate values of MV.
Key Words: stars: AGB and post–AGB — supergiants — techniques: photometric.
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ACKNOWLEDGMENTS
Numerous comments and suggestions made by Prof. Sunetra Giridhar and an anonymous referee are thankfully acknowledged. This work was supported by DGAPA–Universidad Nacional Autónoma de México grant through project IN114309. This research has made extensive use of the Simbad data base operated at CDS, Strasbourg, France and of the NASA ADS Astronomy Query Form.
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