Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001a%26a...375..308c&link_type=abstract
Astronomy and Astrophysics, v.375, p.308-318 (2001)
Astronomy and Astrophysics
Astrophysics
5
Astrometry
Scientific paper
In this paper, we present our results towards the extension of the ICRF to the optical domain down to the 15{th} V magnitude, for some regions of special astronomical interest. This extension is given by accurate positions and proper motions in the ICRS. Present epoch positions were obtained with the CCD transit circle of the Abrahão de Moraes Observatory, in the city of Valinhos - São Paulo. Proper motion derivation is achieved by combining our meridian circle positions with those from available astrometric catalogues and SERC-J plate measurements performed with the MAMA measuring machine (Paris). The final result is presented as a catalogue containing positions, proper motions, magnitudes and cross-identifications with major catalogues for 41 721 objects. A full description of the employed data is given along with an analysis of the uncertainties on positions and proper motions in our final catalogue. On average, stars with V<= 14.0 have positional precisions better than 50 mas in both coordinates, and 100 mas at the detection limit of our instrument (V ~ 16.0). For proper motions, average precisions are better than 4 mas/year, whatever the magnitude, when delta >= -17{o}. To the south of this declination, precisions become magnitude-dependent, providing figures of 3 mas/year when V<=12.0 and reaching 17 mas/year at the detection limit. The declination dependence affects the fainter stars and reflects a feature of our main first epoch material for this magnitude range, the USNO-A2.0 catalogue. The Valinhos CCD transit circle observations cover a variety of regions of great interest. Here, we consider those containing extragalactic radio sources, mostly from ICRF, and pre-main sequence stars in southern star-forming regions (Chamaeleon, Lupus and Upper Scorpius - Ophiuchus), where positions from the SERC-J plates were employed. Based on observations made with the CCD transit circle at the Abrahão de Moraes Observatory, Valinhos - São Paulo. Based on measurements made with the MAMA automatic measuring machine. Table 6 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/375/308
Benevides-Soares Paulo
Camargo I. B. J.
Ducourant Ch.
Teixeira Ramachrisna
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