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J/ApJ/441/307       Proper motions and brightness of Cas A (Anderson+ 1995)

The deceleration powering of synchrotron emission from ejecta components in supernova remnant Cassiopeia A Anderson M.C., Rudnick L. <Astrophys. J. 441, 307 (1995)> =1995ApJ...441..307A (SIMBAD/NED BibCode)
ADC_Keywords: Supernova remnants ; Proper motions ; Radio sources Keywords: ISM: individual (Cassiopeia A) - ISM: kinematics and dynamics - ISM: structure - supernova remnants - techniques: interferometric Abstract: The results of a multiple-epoch radio study of secular changes in the SNR Cassiopeia A are reported and used to construct a model for the dynamical evolution of diffuse and clumpy ejecta components in the remnant. To quantify the current dynamical status of various ejecta components, the proper motions and brightness evolution of a sample of 304 compact radio features have been accurately determined from high-quality interferometric observations of the remnant at lambda=6 and 20cm, spanning a total time baseline of 12yr. A simple model of homologous expansion does not provide a good fit to the measured proper motions of the radio knots. We find that a single estimate of the ejecta expansion age is not appropriate, as the expansion derived from compact features varies azimuthally and radially in the remnant and differs for subsets of knots segregated by brightness. We verify that the bulk of the radio-emitting plasma in Cas A has indeed been significantly decelerated by the current epoch; bulk expansion ages of 2.5-4 times the actual age of the remnant are measured . Based on these dynamical data, and information on the kinematics of the fast moving optical knots. we synthesize a model that directly relates the dynamics of ejecta components in Cas A to various radiative processes. This model is based on the premise that the emission from Cas A, at a variety of wavelengths, is deceleration-powered. If ejecta components are distributed over a range of internal densities, a sequential "turning-on" of components, in order of increasing density, should be observed. A model for the current emission distribution in Cas A, at radio, X-ray, and optical wavelengths, is outlined in terms of deceleration considerations. Objects: -------------------------------------------------------------------- RA (2000) DE Designation(s) -------------------------------------------------------------------- 23 23 12.6 +58 48 48 Cas A = SNR 111.7-02.1 -------------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3 106 304 Results of multi-epoch fits
Byte-by-byte Description of file: table3
Bytes Format Units Label Explanations
1- 3 I3 --- Knot [1/304]+ Knot designation number 5- 7 I3 --- KnotT ? Designation number of Tuffs (1986MNRAS.219...13T), for knots which are clearly in both samples 9- 14 F6.1 arcsec Xpos Epoch 1987 knot position (1) 17- 22 F6.1 arcsec Ypos Epoch 1987 knot position (1) 25- 30 F6.1 arcsec BoxX1 Box defining the regression region used for each knot (1) 33- 38 F6.1 arcsec BoxY1 Box defining the regression region used for each knot (1) 41- 46 F6.1 arcsec BoxX2 Box defining the regression region used for each knot (1) 49- 54 F6.1 arcsec BoxY2 Box defining the regression region used for each knot (1) 56- 61 F6.3 arcsec/yr pmRA Proper motion in right ascension 64- 68 F5.3 arcsec/yr e_pmRA rms uncertainty in pmRA (68% confidence) 71- 76 F6.3 arcsec/yr pmDE Proper motion in declination 79- 83 F5.3 arcsec/yr e_pmDE rms uncertainty in pmDE (68% confidence) 86- 89 F4.1 mJy B Estimate of knot brightness at lambda=6cm (mJy/beam, epoch 1987) 91- 96 F6.3 yr-1 DB/B Annual fractional brightness change relative to the large-scale ring 99-103 F5.3 yr-1 e_DB/B rms uncertainty in DB/B (68% confidence) 106 I1 --- Nobs Number of epochs of data used in multi-epoch determinations
Note (1): Positions measured with respect to the optical expansion center at alpha(1950)= 23h21m11s90, delta(1950) = +58deg32'17.6" (Van den Bergh & Kamper 1983ApJ...268..129V)
History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 02-Oct-1996
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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