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. =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 {mu}as 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 {mu}as/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 {mu}as for a catalogue at epoch J2000.0. Description: The presented catalogue is the ICRF2 catalogue (Fey et al., 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). 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: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file icrf2a.dat 130 3414 ICRF2 catalogue at epoch J2000.0 -------------------------------------------------------------------------------- See also: J/AJ/150/58 : VLBI ICRF2 (Fey+, 2015) Byte-by-byte Description of file: icrf2a.dat -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Acknowledgements: Zinovy Malkin, malkin(at)gao.spb.ru ================================================================================ (End) Zinovy Malkin [Pulkovo Observatory], Patricia Vannier [CDS] 06-Jun-2016