700 pc for its distance.700 pc para la distancia a ella.]]>
700 pc for its distance.]]>
Luis F. Rodríguez and Yolanda Gómez
Centro de Radiostronomía y Astrofísica, UNAM, Apdo. Postal 3–72, (Xangari), 58089 Morelia, Michoacán, México (y.gomez@astrosmo.unam.mx, l.rodriguez@astrosmo.unam.mx)
Received 2006 August 4
Accepted 2006 November 23
RESUMEN
]]> Para la nebulosa planetaria NGC 7009, presentamos una comparación de dos conjuntos de datos sin publicar del archivo del Very Large Array tomados con una separación temporal de 8.09 años para confirmar los movimientos propios observados en el óptico en sus ansas. Determinamos valores de 23±6 y 34±10 mas año – 1 para las ansas este y oeste, respectivamente. Hay evidencia marginal de que las densidades de flujo de los chorros que conectan a las ansas con el cuerpo principal de la nebulosa disminuyeron en un 30% en el periodo que separa a las dos observaciones. También establecemos un límite superior para la expansión del cuerpo principal de la nebulosa planetaria, y obtenemos un límite inferior de700 pc para la distancia a ella.
ABSTRACT
For the planetary nebula NGC 7009, we present a comparison of two unpublished Very Large Array archive data sets taken with a time separation of 8.09 years to confirm the proper motions of its ansae observed in the optical. We determine values of 23±6 and 34±10 mas yr – 1 for the eastern and western ansae, respectively. There is marginal evidence suggesting that the flux densities of the jets that connect the ansae with the main body of the nebula diminished in about 30% over the period between the two observations. We also set an upper limit to the expansion of the main body of the planetary nebula, setting a lower limit of 700 pc for its distance.
Key Words: PLANETARY NEBULAE: INDIVIDUAL (NGC 7009) — TECHNIQUES: INTERFEROMETRIC
DESCARGAR ARTÍCULO EN FORMATO PDF
ACKNOWLEDGEMENT
We thank an anonymous referee for the careful reading of the manuscript. LFR and YG acknowledge the support of DGAPA, Universidad Nacional Autónoma de México, and of Conacyt (México). This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.
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