uvby – β Photoelectric Photometry of the Open Clusters NGC 6811 and NGC 6830¹

J. H. Peña,² L. Fox Machado,³ H. García,⁴ A. Rentería,² S. Skinner,^2,5 A. Espinosa,² and E. Romero²

² Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70–264, México, D. F. México (jhpena@astroscu.unam.mx).

³ Observatorio Astronómico Nacional, Instituto de Astronomía, Ensenada, Apdo. Postal 877, 22800, Ensenada, B. C., México (lfox@astrosen.unam.mx).

⁴ Observatorio Astronómico de la Universidad Nacional Autónoma de Nicaragua, Nicaragua.

⁵ Universidad Nacional de Panamá, Panama.

Received 2010 October 27
Accepted 2011 June 15

RESUMEN

A partir de la fotometría fotoeléctrica uvby — β de los cúmulos abiertos NGC 6811 (75 estrellas) y NGC 6830 (19 estrellas) realizamos la determinación de distancias y, por ende, la pertenencia de las estrellas a cada cúmulo. Asimismo, se determinaron la edad y el enrojecimiento de cada uno. Dado que recientemente se han determinado estrellas variables para el primero, realizamos un estudio de dichas variables.

ABSTRACT

From uvby —β photometry of the open clusters NGC 6811 (75 stars), and NGC 6830 (19 stars) we were able to determine membership of the stars to each cluster, and fix the age and reddening for each. Since several short period stars have recently been found, we have carried out a study of these variables.

Key Words: open clusters and associations: individual (NGC 6811, NGC 6830) — techniques: photometric.

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ACKNOWLEDGMENTS

We would like to thank the staff of the OAN and E. Romero for their assistance in securing the observations. This work was partially supported by PAPIIT IN110102 and IN114309. HG, ER, SS, AE and ARL thank the IA– Universidad Nacional Autónoma de México, for the opportunity to carry out the observations. JHP thanks the hospitality of the UNAN. Typing and proofreading were done by J. Orta, and J. Miller, respectively. C. Guzmán, F. Ruiz and A. Díaz assisted us in the computing. This research has made use of the Simbad databases operated at CDS, Strasbourg, France and NASA ADS Astronomy Query Form.

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NOTAS

¹ Based on observations collected at the San Pedro Mártir Observatory, Mexico.