Radio evolution of the PN NGC 7027 Virtual Observatory Resource

Authors
  1. Zijlstra A.A.
  2. van Hoof P.A.M.
  3. Perley R.A.
  4. Published by
    CDS
Abstract

We present the results of a 25yr program to monitor the radio flux evolution of the planetary nebula NGC 7027. We find significant evolution of the spectral flux densities. The flux density at 1465MHz, where the nebula is optically thick, is increasing at a rate of 0.251+/-0.015%/yr, caused by the expansion of the ionized nebula. At frequencies where the emission is optically thin, the spectral flux density is changing at a rate of -0.145+/-0.005%/yr, caused by a decrease in the number of ionizing photons coming from the central star. A distance of 980+/-100pc is derived. By fitting interpolated models of post-AGB evolution to the observed changes, we find that over the 25yr monitoring period, the stellar temperature has increased by 3900+/-900K and the stellar bolometric luminosity has decreased by 1.75+/-0.5%. We derive a distance-independent stellar mass of 0.655+/-0.010M_{sun}_ adopting the Blocker stellar evolution models, or about 0.04M_{sun}_ higher when using models of Vassiliadis & Wood. A Cloudy photoionization model is used to fit all epochs at all frequencies simultaneously. The differences between the radio flux density predictions and the observed values show some time-independent residuals of typically 1%. A possible explanation is inaccuracies in the radio flux scale of Baars and coworkers. We propose an adjustment to the flux density scale of the primary radio flux calibrator 3C 286, based on the Cloudy model of NGC 7027. We also calculate precise flux densities for NGC 7027 for all standard continuum bands used at the VLA, as well as for some new 30 GHz experiments.

Keywords
  1. planetary-nebulae
  2. radio-continuum-emission
Bibliographic source Bibcode
2008ApJ...681.1296Z
See also HTML
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/681/1296
IVOA Identifier IVOID
ivo://CDS.VizieR/J/ApJ/681/1296
Document Object Identifer DOI
doi:10.26093/cds/vizier.16811296

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History

2010-11-23T07:51:45Z
Resource record created
2010-11-23T07:51:45Z
Created
2010-12-06T11:26:56Z
Updated

Contact

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