I/340 UCAC5 Catalogue (Zacharias+ 2017) ================================================================================ UCAC5: New Proper Motions using Gaia DR1. Zacharias N., Finch C., Frouard J. =2017yCat.1340....0Z =2017AJ....153..166Z ================================================================================ ADC_Keywords: Surveys ; Positional data ; Proper motions Keywords: astrometry, proper motions Abstract: New astrometric reductions of the US Naval Observatory CCD Astrograph Catalog (UCAC) all-sky observations were performed from first principles using the TGAS stars in the 8 to 11 magnitude range as reference star catalog. Significant improvements in the astrometric solutions were obtained and the UCAC5 catalog of mean positions at a mean epoch near 2001 was generated. By combining UCAC5 with Gaia DR1 data new proper motions on the Gaia coordinate system for over 107 million stars were obtained with typical accuracies of 1 to 2mas/yr (R=11 to 15mag), and about 5mas/yr at 16th mag. Proper motions of most TGAS stars are improved over their Gaia data and the precision level of TGAS proper motions is extended to many millions more, fainter stars. External comparisons were made using stellar cluster fields and extragalactic sources. The TGAS data allow us to derive the limiting precision of the UCAC x, y data, which is significantly better than 1/100 pixel. Description: The UCAC5 positions on the Gaia coordinate system provide additional data of similar quality to the Hipparcos mission Tycho star observations and thus have the potential to improve the TGAS proper motions. UCAC5 provides new, accurate proper motions for millions of more stars fainter than TGAS, which will allow astronomers to have a preview into research possible only with the next Gaia data release. At the faint end UCAC5 proper motion errors are relatively large due to the low S/N ratio of these observations. Better proper motions for stars fainter than about 15th mag are available from proper motions obtained by combining NOMAD (Cat. I/297/) with Gaia DR1 (Cat. I/337) (catalog of 503 million stars is available upon request), or the recently published PPMXL re-reduction, called the HSOY (Altmann et al., 2017, Cat. I/339) catalog. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file ucac5.sam 161 1000 UCAC5 catalog (107,758,513 sources) readmeU5.txt 79 578 Description of UCAC5 -------------------------------------------------------------------------------- See also: I/297 : NOMAD Catalog (Zacharias+ 2005) I/337 : Gaia DR1 (Gaia Collaboration, 2016) I/339 : Hot Stuff for One Year (HSOY) (Altmann+, 2017) Byte-by-byte Description of file: ucac5.sam -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 11 F11.7 deg RAdeg UCAC right ascension (J2000) at epoch "EPucac" on Gaia reference frame (ira) 13- 23 F11.7 deg DEdeg UCAC declination (J2000) at epoch "EPucac" on Gaia reference frame (idc) 25- 43 I19 --- SrcIDgaia Gaia source ID (srcid) 45- 55 F11.7 deg RAgaia Gaia right ascension (ICRS) at epoch 2015.0 (rag) (1) 57- 67 F11.7 deg DEgaia Gaia declination (ICRS) at epoch 2015.0 (dcg) (1) 69- 73 F5.1 mas e_RAgaia rms uncertainty on RAgaia (erg) (1) 75- 78 F4.1 mas e_DEgaia rms uncertainty on DEgaia (edg) (1) 80 I1 --- Org [1/3] TGAS/NOMAD flag (flg) (2) 82- 83 I2 --- Nu Number of images used for mean position (nu) 85- 92 F8.3 yr EPucac UCAC epoch (epu) 94-100 F7.1 mas/yr pmRA UCAC/Gaia proper motion in RA*cosDE (pmur) 102-108 F7.1 mas/yr pmDE UCAC/Gaia proper motion in DE (pmud) 110-114 F5.1 mas/yr e_pmRA rms uncertainty on pmRA (pmer) 116-119 F4.1 mas/yr e_pmDE rms uncertainty on pmDE (pmed) 121-126 F6.3 mag Gmag Gaia G magnitude (gmag) 128-133 F6.3 mag f.mag ? Means UCAC model magnitude (umag) 135-140 F6.3 mag Rmag ? Photographic R magnitude from NOMAD (rmag) 142-147 F6.3 mag Jmag ? 2MASS J magnitude (jmag) 149-154 F6.3 mag Hmag ? 2MASS H magnitude (hmag) 156-161 F6.3 mag Kmag ? 2MASS K magnitude (kmag) -------------------------------------------------------------------------------- Note (1): The precision of the Gaia position is mas, rounded to integer, while the precision of Gaia position errors is 0.1mas, also rounded to integer. It means that at epoch 2015 the rounded error on Gaia positions is higher than the statistical error. The Gaia 2015 epoch positions and errors were added for convenience, using Gaia data as reference stars at a different epoch than 2015. Thus the position errors at those epochs would be dominated by the proper motion errors. Note (2): Flag as follows: 1 = TGAS 2 = not TGAS, in NOMAD 3 = neither -------------------------------------------------------------------------------- Acknowledgements: Norbert Zacharias, nz(at)usno.navy.mil or nzIAUc8(at)gmail.com ================================================================================ (End) Patricia Vannier [CDS] 13-Mar-2017