J/MNRAS/445/845 Implications of the Galactic aberration for CRF (Malkin, 2014)
On the implications of the Galactic aberration in proper motions for the
Celestial Reference Frame.
Malkin Z.
<Mon. Not. R. Astron. Soc., 445, 845-849 (2014)>
=2014MNRAS.445..845M 2014MNRAS.445..845M (SIMBAD/NED BibCode)
ADC_Keywords: Interferometry ; VLBI ; Positional data
Keywords: methods: data analysis - astrometry - reference systems
Abstract:
During the last few years, much attention has been paid to the
astrometric implications of the galactic aberration in proper motions
(GA). This effect causes systematic errors in astrometric measurements
at a µas level. Some authors consider it so serious that it
requires redefinition of the Celestial Reference Frame (CRF). We argue
that such attention to the GA is exaggerated too much. It is just a
small astrometric correction that must be taken into account during
highly accurate astrometric and geodetic data processing. The accuracy
of this correction depends on the accuracy of the Galactic rotation
parameters and, for most applications, on the accuracy of the rotation
matrix between Galactic and equatorial systems. Our analysis has shown
that our current knowledge of these two factors is sufficient to
compute the correction of the GA with an accuracy better than 10 per
cent. The remaining effect at the level of a few tenths µas/yr is
negligible nowadays. Another consequence of introducing the GA
correction is the necessity to return to classical astrometric
modelling of the extragalactic radio source position - derived by
very-long-baseline interferometry (VLBI) - by the linear trend model.
Changing the current paradigm of the VLBI-derived CRF, based on the
assumption of zero motion of radio sources, to classical one leads to
bias in the radio source positions of up to several tens of µas for
a catalogue at epoch J2000.0.
Description:
The presented catalogue is the ICRF2 catalogue (Fey et al.,
2015AJ....150...58F 2015AJ....150...58F) brought to the epoch J2000.0 by applying the
source proper motions caused by the Galactic aberration using the
algorithm described by Malkin (2014MNRAS.445..845M 2014MNRAS.445..845M). The file format
and content are the same as for the ICRF2 catalogue (Vizier
J/AJ/150/58) except the coordinates of the ICRF2 radio sources (bytes
32-66).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
icrf2a.dat 130 3414 ICRF2 catalogue at epoch J2000.0
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See also:
J/AJ/150/58 : VLBI ICRF2 (Fey+, 2015)
Byte-by-byte Description of file: icrf2a.dat
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Bytes Format Units Label Explanations
-------------------------------------------------------------------------------
1- 4 A4 --- --- [ICRF]
6- 21 A16 --- ICRF2 Designation in International Celestial
Reference Frame (ICRF2)
23- 30 A8 --- IERS Designation in International Earth Rotation and
Reference Systems Service (IERS)
32- 33 I2 h RAh Hour of Right Ascension (J2000)
35- 36 I2 min RAm Minute of Right Ascension (J2000)
38- 48 F11.8 s RAs Second of Right Ascension (J2000)
50 A1 --- DE- Sign of the Declination (J2000)
51- 52 I2 deg DEd Degree of Declination (J2000)
54- 55 I2 arcmin DEm Arcminute of Declination (J2000)
57- 66 F10.7 arcsec DEs Arcsecond of Declination (J2000)
68- 77 F10.8 s e_RAs Uncertainty in RAs
79- 87 F9.7 arcsec e_DEs Uncertainty in DEs
89- 94 F6.3 --- Corr Correlation between estimates of RA and DE
96-102 F7.1 d MJD Modified Julian date of observation mean
104-110 F7.1 d MJD0 Modified Julian date of observation start
112-118 F7.1 d MJD1 Modified Julian date of observation end
120-123 I4 --- Nexp Number of experiments
125-130 I6 --- Nobs Number of observations
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Acknowledgements:
Zinovy Malkin, malkin(at)gao.spb.ru
(End) Zinovy Malkin [Pulkovo Observatory], Patricia Vannier [CDS] 06-Jun-2016