An approach to effective temperature and surface gravity in post–AGB and RV Tauri stars in the near–IR region

 

R. E. Molina

 

Laboratorio de Investigación en Física Aplicada y Computacional, Universidad Nacional Experimental del Táchira, Venezuela. (rmolina@unet.edu.ve).

 

Received 2011 October 20.
Accepted 2012 January 5.

 

RESUMEN

Se determina la temperatura efectiva y la gravedad superficial de un conjunto de estrellas evolucionadas post–AGB y RV Tau a partir de ecuaciones empóricas usando como calibradores los colores intrínsecos de la fotometría 2MASS (Two Micron All Sky Survey). Analizamos un total de 36 estrellas de las cuales 25 son post–AGB y las restantes 11 son RV Tau respectivamente. Utilizamos un grupo de 11 estrellas con medidas de paralaje como calibradores en la determinaciíon de la magnitud absoluta en la banda J. Los resultados para la T_eff y la log g derivadas de los colores intrínsecos (J — H)₀ y (H — K_s)₀ alcanzan una dispersión de 220 K y 0.27, respectivamente. Estimamos la magnitud absoluta en la banda J con una precisión de 0.28 mag. Esto nos indica que los colores (J — H)₀ y (H — K_s)₀ presentan sensibilidad a dicho parámetro.

 

ABSTRACT

A number of empirical correlations that allow us to calculate the effective temperature and surface gravity for a set of evolved post–AGB and RV Tauri stars are determined using as calibrators the intrinsic colors of 2MASS (Two Micron All Sky Survey) photometry. We have analyzed a total sample of 36 stars of which 25 are post–AGB stars and 11 are RV Tauri stars, respectively. A group of 11 stars with parallax measures were used as calibrators of the absolute magnitude. The result for T_eff and log g from intrinsic colors (J — H)₀ and (H — K_s)₀ at the near–infrared pass bands reach a dispersion of 220 K and 0.27, respectively. We can estimate the absolute magnitude using the intrinsic color in the near–infrared band with an uncertainty of 0.28 mag. This indicates that (J — H)₀ and (H — K_s)₀ show sensitivity to the absolute magnitude.

Key Words: stars: fundamental parameters — stars: AGB and post–AGB.

 

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