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J/A+A/375/661       Stability of VLBI reference frame        (Gontier+, 2001)

Stability of the extragalactic VLBI reference frame Gontier A.-M., Le Bail K., Feissel M., Eubanks T.M. <Astron. Astrophys. 375, 661 (2001)> =2001A&A...375..661G
ADC_Keywords: QSOs ; VLBI ; Positional data ; References Keywords: quasars - techniques: interferometric - astrometry - reference systems Description: The file table 2 gives the results of various tests and noise measurements performed on time serie of extragalactic radio source coordinates. Systematic and random behaviours in time serie of individual determinations of cooordinates for 283 sources over 1987-1999 are investigated. The random variability of the source coordinates is characterized by the χ2 test (Bevington, 1969, p.187) and the "goodness of fit (gof)" (Bevington, 1969, p.188). The Allan variance method (Allan, 1966, Proc. IEEE, vol. 54, 221) is used to investigate spectral characteristics of the time series. The source structure index (Fey & Charlot, 1997ApJS..111...95F, 2000, Cat. J/ApJS/128/17) qualifies the level of position disturbance expected at the date of the map (1 for the less disturbed, 4 for the most disturbed). The estimation of "linear rates" in the coordinates is a qualifier of the systematic parts of the source instability. This table contains the 283 best observed sources and is divided in three parts, with the left hand side giving general information and counts, the middle part giving statistics in the source local frame, and the right hand side giving statistics in the equatorial frame. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 96 264 Observational and statistical characteristics of the sources over 1987-1999, in the local and equatorial coordinate systems table2.tex 76 626 LaTeX version of the table
See also: J/AJ/110/880 : Radio reference frame (Johnston+ 1995) J/ApJS/128/17 : VLBA obs. of radio reference frame sources. III. (Fey+, 2000) I/171 : Astrographic Catalog Reference Stars (ACRS) (Corbin+ 1991) I/172 : International Reference Stars (IRS) (Corbin 1991) I/246 : The ACT Reference Catalog (Urban+ 1997) I/251 : VLBI International Celestial Reference Frame (ICRF) (Ma+, 1997) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 8 A8 --- IERS IERS designation of the radio source 10 A1 --- n_IERS [dcon] ICRF status of the source (1) 12- 15 I4 --- Nses Number of sessions with more than two observations of the source. 17- 18 I2 --- Nyears Number of years with observations of the source in at least six sessions. 20- 22 I3 deg Angle ? Angle of the axis of maximum local variability with the declination axis. 24 A1 --- l_gofPos Limit flag on gofPos 25- 29 F5.1 --- gofPos Goodness of fit of the yearly coordinate in the direction of maximum local variability. 31- 36 F6.2 --- e_Pos ? Allan standard error of yearly coordinate in the direction of maximum local variability 38 I1 --- Index ? Fey & Charlot (1997ApJS..111...95F and 2000, Cat. J/ApJS/128/17) source structure index 40- 43 I4 yr EpIndex ? Epoch of source structure index 45 A1 --- Noise [WF] Spectral type of noise in the direction of maximum local variability: White noise (W) or Flicker noise (F). 47- 51 F5.2 mas/yr Rate ? Rate of apparent motion in the direction of maximum local variability 53- 56 F4.2 mas/yr e_Rate ? rms uncertainty on Rate 58 A1 --- n2RA [#] # marks poor estimates 59- 62 F4.1 --- 2_RA ? χ2 of individual right ascensions 64 A1 --- lgof2RA Limit flag on gof2_RA 65- 69 F5.1 --- gof2_RA Goodness of fit of yearly right ascensions 71- 75 F5.2 --- e_RAcosDE ? Allan standard error of yearly RAcosDE 77 A1 --- n2DE [#] # marks poor estimates 78- 81 F4.1 --- 2_DE ? χ2 of individual declinations 83 A1 --- lgof2RE Limit flag on gof2_RE 84- 89 F6.1 --- gof2_RE Goodness of fit of yearly declinations 91- 96 F6.2 --- e_DE ? Allan standard error of yearly declinations
Note (1): ICRF status of the source: d: definition c: candidate o: other n: new
Acknowledgements: Anne-Marie Gontier References: Bevington, P.R. 1969, Data reduction and Error analysis for the physical sciences, McGraw-Hill, New York.
(End) Patricia Bauer [CDS] 09-Jul-2001
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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