J/AJ/125/2728ivo://CDS.VizieR/J/AJ/125/2728doi:10.26093/cds/vizier.51252728CDSAssafin M.Zacharias N.Rafferty T.J.Zacharias M.I.Da Silva Neto D.N.,Andrei A.H.Vieira Martins R.2023-04-06T16:50:55Z2004-07-07T14:12:22ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frastrometryquasarsNew optical positions on the 30mas precision level have been obtained for 172 extragalactic International Celestial Reference Frame (ICRF) sources mainly in the range -30{deg}<=DE<=+25{deg}. Results are presented from a pilot investigation including four Cerro Tololo (CTIO) 0.9m runs (1999-2001). Reference stars in the R~10-16.5mag used. Systematic errors have been investigated, and a field distortion pattern based on the residuals has been removed. The errors of the fainter stars in the CTIO data were assessed by evaluating an auxiliary set of CCD observations of common ICRF sources, taken at the 1.60m Cassegrain telescope of the Laboratorio Nacional de Astrofisica, Brazil. A significant improvement in the optical positions was achieved over a previous determination of source positions. The mean optical positions are compared with the ICRF radio positions. The overall optical minus radio offsets are -6 and -15mas for right ascension and declination, respectively. The formal internal error of these mean offsets is ~2.3mas. his indicates a possible systematic error in the UCAC declinations of 10 to 15mas. Both the optical counterpart observations and the optical reference stars are observed about 9 yr after the Hipparcos mean epoch, and our results set an upper limit for a possible Hipparcos system rotation with respect to the International Celestial Reference System for the z-axis of about 0.7mas/yr.2003AJ....125.2728Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/125/2728CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/251 : VLBI International Celestial Reference Frame (ICRF) (Ma+, 1997)I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)I/268 : UCAC1 Catalogue (Zacharias+ 2000)I/294 : The UCAC2 Bright Star Supplement (Urban+, 2004)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/125/2728https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/125/2728http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/125/2728https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/125/2728https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/125/2728http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/125/2728GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/125/2728/table4 (Optical positions for 172 ICRF sources from CTIO CCD observations)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/125/2728/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/125/2728/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/125/2728/table4?GETtext/xml+votable180.050000true1.557885-6.3931513890.0055555555555555566/60 124 304 532 4436 4448 4696 4770 4820 5154 5163 6164 8199 8299 8345 8487 8717 12301 12352 12475 12580 16962 17110 17188 17215 17351 17516 17529 17541 17579 17734 17791 17857 17909 18002 18022 18035 18037 18084 18214 18271 18378 18457 18506 18624 18661 18669 18718 18755 18871 18907 19088 19101 19190 19271 19370 19398 19523 19567 19609 19629 21012 21564 21758 21768 21924 21935 21960 21968 21972 22363 22396 22501 22658-22659 22917 22950 22965 23099 23121 23127 23335 23383 23478 23761 24003 24084 24116 24123 25196 25302 25428 25503 25630 25742 25864 25990 26000 26083 26100 26115 26131 26292 26301 26303 26363 26550 26900 26966 26983 27060 27220 27310 27322 27423 27466 27514 27583 27909 28167 28184 28208 28339 28453-28454 29714 29795 31211 31334 31355 31391 31430 31451 31529 31535 31664 34675 34699 35786 35801 36155 36188 36417 36554 37994 38189 39848 40344 40692 40730 43399 44614 44658 44661 44776 44805 44832 44899 46964 47016 47080 47540 47941 48023 48123 48228 48362 48589 48595 48610 48965https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/125/2728?format=asciiOpticaldefaultJ/AJ/125/2728/table4Optical positions for 172 ICRF sources from CTIO CCD observationsEpochMean epoch of the observationsyrtime.epochfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintICRFThe ICRF source namemeta.id;meta.maincharRAJ2000Hour of optical right ascension (ICRF)pos.eq.ra;meta.mainDEJ2000Degree of optical declination (ICRF)pos.eq.dec;meta.maine_RAs? Standard deviation of the mean in RA (1)arcsecstat.errorfloatnullablee_DEs? Standard deviation of the mean in DE (1)arcsecstat.errorfloatnullableNumNumber of CCD observationsmeta.numberintRmagThe UCAC R-band magnitudemagphot.mag;em.opt.Rfloate_Rmag? Standard deviation of the mean in Rmag (1)magstat.errorfloatnullableDRAcosDERight ascension optical-radio offsetarcsecpos.eq.ra;arith.difffloatDDEDeclination optical-radio offsetarcsecpos.eq.dec;arith.difffloatsigmaRAMean right ascension error of the "plate solution"arcsecstat.errorfloatsigmaDEMean declination error of the "plate solution"arcsecstat.errorfloatCommSource CCD image peculiarity comments (2)meta.notechar