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I/294A              The UCAC2 Bright Star Supplement              (Urban+, 2006)

The UCAC2 Bright Star Supplement. Urban S.E., Zacharias N., Wycoff G.L. U.S. Naval Observatory, Washington D.C. 2004-2006 <Astron. J. (unpublished) (2004)>
ADC_Keywords: Positional data ; Proper motions ; Stellar distribution ; Surveys Keywords: astrometry - stars - fundamental parameters - catalogs - proper motions - cross identifications Abstract: The UCAC2 Bright Star Supplement (UCAC2 BSS) is meant to be used with the Second U.S. Naval Observatory CCD Astrograph Catalog (UCAC2, CDS Catalogue number I/289) to fill in the missing bright stars and yet-to-be observed northern regions of the UCAC2. In total 430,000 stars, mostly from the region north of +40 degrees declination, make up this supplementary data set. All astrometric data were extracted from either the Hipparcos Catalogue or the Tycho-2 Catalogue; photometric data were extracted from the Hipparcos, Tycho-2, and 2MASS catalogues. Cross references between the data sources are given. Description: The Second U.S. Naval Observatory CCD Astrograph Catalog (UCAC2) has now been completed and distributed (see CDS catalogue I/289). The UCAC2 catalogue contains stars in the R ∼ 8-16 magnitude range with sky coverage from the South Celestial Pole to a ragged northern boundary between declination +40 to +55 degrees. Details of that catalogue and project can be found elsewhere (see UCAC web page at http://ad.usno.navy.mil/ucac/ ). Two noticeable features of the UCAC2 are its lack of bright stars and its incomplete sky coverage. The former is a result of the finite dynamic range of the data acquisition system and observing procedures; they are optimized for the magnitude range of r∼8-16. The brightest stars are over-exposed and little astrometric information is gained. The latter is a result of the on-going nature of the project. The UCAC2 covers over 85% of the sky; the remaining Northern Celestial Pole area is currently being observed and reduced. It is expected that the final UCAC catalogue will be released in 2006. These two features -- the lack of bright stars and the lack of full sky coverage -- are the reasoning behind the UCAC2 Bright Star Supplement (UCAC2 BSS). The UCAC2 BSS is somewhat of a misnomer on two counts. First, there are no UCAC2 data in it. Instead, all astrometric data were extracted from the Hipparcos main catalog (HIP), the Hipparcos Double and Multiple System Annex (DMSA), the Tycho-2 main catalog, or the Tycho-2 Supplement 1. Photometric data were taken from the above catalogues and the Two-Micron All Sky Survey (2MASS). Second, the UCAC2 BSS contains not only bright stars, but all stars from the above mentioned catalogs not found in the UCAC2. This not only includes the spatial area covered by the UCAC2, but also the far northern regions. For this reason, most stars in the UCAC2 BSS are north of +40 degrees. Additional information, including a very extensive catalogue introduction can be found on the UCAC project website at http://ad.usno.navy.mil/ucac/ . This website also contains a binary version of the UCAC2 BSS catalog. This version is very similar in format to the UCAC2 binary data, therefore much of the same software can be utilized. The software can be downloaded from the project webpage. UCAC2 Bright Star Supplement Data Format: ---------------------------------------- The data are arranged in 5 degree zones of declination, starting from the South Celestial Pole, and are sorted by Right Ascension within each zone. The running ID numbers go from 50,000,001 to 50,430,000; they are unique, and have no gaps. The start of the ID number at 50,000,001 was chosen so it did not conflict with any UCAC2 ID number. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file ucac2bss.dat 218 430000 UCAC Bright Star Supplement
See also: http://ad.usno.navy.mil/ucac/ : the UCAC Home Page I/289 : The UCAC2 Catalogue (Zacharias+ 2003) I/239 : The Hipparcos and Tycho Catalogues (ESA 1997) I/259 : The Tycho-2 Catalogue (Hog+ 2000) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) Byte-by-byte Description of file: ucac2bss.dat
Bytes Format Units Label Explanations
1- 8 I8 --- ID [50000001,] UCAC2 BSS identifier (1) 10- 21 F12.8 deg RAdeg RA at epoch J2000.0 (ICRS) (2) 23- 34 F12.8 deg DEdeg Dec at epoch J2000.0 (ICRS) (2) 36- 41 F6.2 mas e_RAdeg S.e. of RA at central ep. (*cos DE) (3) 43- 48 F6.2 mas e_DEdeg S.e. of Dec at central epoch (3) 50 A1 --- src Source catalog for astrometry (4) 52- 58 F7.2 yr EpRAm Central epoch for mean RA (5) 60- 66 F7.2 yr EpDEm Central epoch for mean DE (5) 68- 75 F8.2 mas/yr pmRA ? Proper motion in RA (no cos DE) (6) 77- 85 F9.3 mas/yr pmDE ? Proper motion in DE (6) 86- 91 F6.3 mas/yr e_pmRA ? S.e. of pmRA (*cos DE) (7) 92- 96 F5.2 mas/yr e_pmDE ? S.e. of pmDE (7) 98-102 A5 --- q_pmRA Goodness of fit for pmRA (8) 104-108 A5 --- q_pmDE Goodness of fit for pmDE (8) 110-115 F6.3 mag B-V ? Johnson B-V color index (9) 117-120 F4.2 mag V-I ? Cousins V-I color index (10) 122 A1 --- HvarType Variability type (11) 124-129 F6.2 mag Vmag ? Johnson V magnitude (12) 131-136 F6.3 mag BTmag ? Mean Tycho b magnitude (13) 138-143 F6.3 mag VTmag ? Mean Tycho v magnitude (14) 145-150 F6.3 mag Hpmag ? Median mag in Hipparcos system (15) 152 A1 --- VarFlag HIP course variability flag (16) 154-157 I4 --- TYC1 ? Tycho-2 number (17) 158 A1 --- --- [0] (17) 159-163 I5 --- TYC2 ? Tycho-2 number (17) 164 A1 --- --- [0] (17) 165 I1 --- TYC3 ? Tycho-2 number (17) 167 I1 --- r_TYC2 ? Source of Tycho-2 (18) 169-174 I6 --- HIP ? Hipparcos number (19) 176 A1 --- m_HIP HIP component identifier (20) 178-187 I10 --- 2mID ? 2MASS pts_key star id (21) 189-194 F6.3 mag 2mJmag ? 2MASS J magnitude (22) 196-201 F6.3 mag 2mHmag ? 2MASS H magnitude (22) 203-208 F6.3 mag 2mKsmag ? 2MASS K_s_ magnitude (22) 210-212 A3 --- 2mflags ? 2MASS photo. quality flags (23) 214-216 A3 --- 2mcc ? 2MASS cc_flg (24) 218 A1 --- astflg Warning flag for astrometry (25)
Note (1): The ID field provides the UCAC2 Bright Star Supplement identification number. This is a running number that can be used to link the information between the ASCII version and the binary version. Notice that this ID number changed between the original version and this version, see the "History" section below; the old numbering is available from the on-line version of the catalog if necessary. Note (2): The RA and DE fields provide positions on the International Celestial Reference System (ICRS) as represented by the Hipparcos/Tycho-2 catalogs. The epochs are J2000.0, with conversions being made (where necessary) using the NOVAS software package. In cases where there is no proper motion (fields 9 and 10 are " ", or field 33 is "N"), this position refers to the epoch given in field 4 (for RA) or field 5 (for DE). Note (3): The e_RAm and e_DEm fields provide the standard errors at the central epochs. Note (4): The src field provides the source catalog used for all astrometric data for that star (position, proper motion and errors). It has the following meaning: H = Hipparcos main catalog D = Hipparcos Double and Multiple Star Annex (DMSA) T = Tycho-2 main catalog S = Tycho-2 supplement 1 Note (5): The EpRAm and EpDEm fields provide the central epochs of the astrometric data. The central epoch is the epoch with the lowest positional errors (e_RAm, e_DEm). For all other epochs (including "J2000.0" which corresponds to the RA, DE positions given), the errors in position can be computed as: e_RA (at epoch T) = SQRT ( e_RAm**2 + (e_pmRA * (T-EpRAm))**2) e_DE (at epoch T) = SQRT ( e_DEm**2 + (e_pmDE * (T-EpDEm))**2) Thus, for all epochs other than EpRAm or EpDEm, the positional errors for RA and Dec, respectively, increase going forward or backward in time. Values for EpRAm and EpDEm are usually not equal due to different weights assigned to coordinates in the individual catalogs used in determining the mean positions and proper motions. Note (6): The fields pmRA and pmDE provide the proper motion in right ascension and declination, respectively, referred to the central epoch. Note that pmRA is without cos(DE), thus these values can be large for stars close to the pole. This is done so the units for pmRA and RA are similar, thus facilitating easy computation to change epochs. Both pmRA and pmDE can directly be used to update a star's position for proper motion by: RA (epoch T) = RA + pmRA * (T - 2000.0)/3.6e6 DE (epoch T) = DE + pmDE * (T - 2000.0)/3.6e6 Note, values for RA, and DE provided here are in degrees, while the pmRA and pmDE provided here are in mas/yr, thus the factor 3600000 in the equations. Also note that the above formulas do not account for so-called "second-order" effects, such as the change in the apparent direction of the pole as seen from a star as proper motion is applied or the apparent acceleration of a proper motion due to the distance to a star changing. The first effect is negligible in most instances unless a star has a very high proper motion and is very close to the pole and that proper motion is being applied for many years. The second effect is negligible in most cases unless a star is nearby and has a large radial velocity (often this is unknown). Where no proper motions exist, these fields are " ". Note (7): e_pmRA and e_pmDE are the standard errors of pmRA, pmDE respectively. Note e_pmRA does include cos(DE), which makes both e_pmRA and e_pmDE of comparable size in the tangential plane. Where no proper motions exist, these fields are "_" Note (8): The q_pmRA and q_pmDE fields provide "goodness-of-fit" parameters to give the user some idea of how well determined the astrometry is. For stars with "H" in the src field, the values were extracted from field H30; values above +3 indicate a poor fit to the data. For stars with "D" in the src field, the values were extracted from field DC5. For these records, "A" indicates a good solution, "B" indicates a fair, moderately reliable solution, "C" indicates a poor, less reliable solution, and "D" indicates an uncertain solution. For stars with "T" in the src field, the data gives information on how well the computed proper motions actually fit the catalog positions used to compute them. The values q_pmRA and q_pmDE are actually ratios, "scatter error pm"/e_pmRA (or e_pmDC). Thus, when the actual fit of the proper motion to the catalog positions is better than the formal, model errors (e_pmRA, e_pmDE), the ratio is smaller than 1. In the opposite case, the ratio is larger than 1. Stars with q_pmRA or q_pmDE values exceeding 5 should be used with caution. Values exceeding 9.9 are truncated to 9.90. Note, this value is only defined when the number of catalog positions used to compute the proper motions is greater than 2, else an underscore is given. Note (8): The q_pmRA and q_pmDE fields provide "goodness-of-fit" parameters to give the user some idea of how well determined the astrometry is. For stars with "H" in the src field, the values were extracted from field H30; values above +3 indicate a poor fit to the data. For stars with "D" in the src field, the values were extracted from field DC5. For these records, "A" indicates a good solution, "B" indicates a fair, moderately reliable solution, "C" indicates a poor, less reliable solution, and "D" indicates an uncertain solution. For stars with "T" in the src field, the data gives information on how well the computed proper motions actually fit the catalog positions used to compute them. The values q_pmRA and q_pmDE are actually ratios, "scatter error pm"/e_pmRA (or e_pmDC). Thus, when the actual fit of the proper motion to the catalog positions is better than the formal, model errors (e_pmRA, e_pmDE), the ratio is smaller than 1. In the opposite case, the ratio is larger than 1. Stars with q_pmRA or q_pmDE values exceeding 5 should be used with caution. Values exceeding 9.9 are truncated to 9.90. Note, this value is only defined when the number of catalog positions used to compute the proper motions is greater than 2, else an underscore is given. Note (9): The B-V field provides the Johnson B-V color index. It is only given for stars with an "H" in the src field; it was extracted from HIP field H37. Note (10): The V-I field provides the Cousins V-I color index. It is only given for stars with an "H" in the src field; it was extracted from HIP field H40. Note (11): The HvarType field provides the Hipparcos variability type. It is only given for stars with an "H" in the src field; it was extracted from HIP field H52 and means: C = no variability detected ("constant") D = duplicity-induced variability M = possibly micro-variable (amplitude < 0.03mag) P = periodic variable R = V-I colour index was revised due to variability analysis U = unsolved variable which does not fall in the other categories Note (12): The Vmag field provides the Johnson V magnitude. It is only given for stars with an "H" in the src field; it was extracted from HIP field H5. Note (13): The B_T field provides the mean Tycho b magnitude. For stars with "H" in the src field, the data were extracted from HIP field H32. For stars with "D" in the src field, the data were extracted from DMSA field DC11. For stars with "T" in the src field, the data were extracted from the Tycho-2 BT field. For stars with "S" in the src field, the data were extracted from the Tycho-2 BT field. The users should note that stars from HIP, DMSA, and Tycho-2 Supplement 1 use the initial Tycho magnitudes, whereas the Tycho-2 stars use the Tycho-2 magnitudes. Note (14): The V_T field provides the mean Tycho v magnitude. For stars with "H" in the src field, the data were extracted from HIP field H34. For stars with "D" in the src field, the data were extracted from DMSA field DC13. For stars with "T" in the src field, the data were extracted from the Tycho-2 VT field. For stars with "S" in the src field, the data were extracted from the Tycho-1 VT field. The users should note that stars from HIP, DMSA, and Tycho-2 Supplement 1 use the initial Tycho magnitudes, whereas the Tycho-2 stars use the Tycho-2 magnitudes. Note (15): The Hpmag field provides the median magnitude in the Hipparcos photometric system. For stars with "H" in the src field, the data were extracted from HIP field H44. For stars with "D" in the src field, the data were extracted from DMSA field DC9. There is no comparable magnitude in the Tycho-2 data, so stars with "T" or "D" in the src field are filled with underscores. Note (16): The VarFlag field provides the Hipparcos course variability flag. It is only given for stars with an "H" in the src field; it was extracted from HIP field H6. A flag in this field indicates the star is a variable in the Hipparcos photometric system at the following level: 1 = < 0.06 mag 2 = 0.06 - 0.6 mag 3 = > 0.6 mag Note (17): The TYC-2 field (bytes 162-165) provides the Tycho-2 number. It is extracted from the Tycho-2 catalog fields "TYC1", "TYC2", and "TYC3". Zeros are embedded where blanks existed in the Tycho-2 catalog, therefore all IDs are 12 digits in length. Note (18): The r_TYC-2 field provides the source of the Tycho-2 number. It shows whether it was extracted from the main catalog or a supplement. " " = no Tycho-2 number 0 = extracted from Tycho-2 main catalog 1 = extracted from Tycho-2 Supplement 1 Note (19): The HIP field provides the Hipparcos number. For stars with an "H" in the src field, it was extracted from HIP field H1. For stars with a "D" in the src field, it was extracted from DMSA field DC8. For stars with "T" or "S" in the src field, it was extracted from the HIP field of the respective catalog. Note (20): The comp_id field provides the Hipparcos component identifier. It is only provided for those stars with a "D" in the src field. It was extracted from DMSA field DC7. Note (21): The 2m_id field provides the 2MASS identifier. Given is the "pts_key" star identification number found in the 2MASS point source catalog. Note (22): The 2m_J, 2m_H, and 2m_Ks fields provide the J, H, and Ks magnitudes of 2MASS. They are extracted directly from the 2MASS catalog. Note (23): The 2m_ph field provides the 2MASS photometric quality flags as extracted from the 2MASS catalog. For each color (J, H, K_s) one letter is given. Specific meanings can be found in the 2MASS documentation. General meanings are: A or B = good detections (snr > 7) C or D = weak detections other = the 2MASS documentation should be consulted. Note (24): The 2m_cc field provides the 2MASS contamination and confusion flags as extracted from the 2MASS point source catalog. They indicate the amount of contamination and confusion seen in the 2MASS data. For each color (J, H, K_s) one value is given. Specific meanings can be found in the 2MASS documentation. General meanings are: 0 = no artifacts or contamination seen c = confusion with nearby brighter source other = the 2MASS documentation should be consulted. Note (25): The astflg provides the user with a warning if a star is known to have either non-linear astrometry (in the case of orbit stars, for example), the proper motion was based on photocenter data, the proper motion error in either coordinate is 25.0 mas/yr or higher, or the proper motion is undetermined. "*" = star is Hipparcos G,V,O, or X (in H59); or star's proper motion error in either coordinate is 25.0mas/yr or higher; or star is Tycho-2 photocenter solution "N" = proper motion for this star is not determined
Acknowledgements: The UCAC team is pleased to acknowledge the great effort by the Hipparcos team, the Tycho-2 team, and the Two-Micron All Sky Survey team. Without the great products that they produced, the UCAC2 Bright Star Supplement would not exist. History: * 12-Mar-2004: Original version, from Sean Urban * 14-Oct-2009: Installation of the 2006 version having the same set of stars, but with different ID numbers in the same range 50000001-50430000. The change followed a re-work of BSS at USNO. References: Urban S.E., Zacharias, N, and Wycoff, G.L., 2004, AJ, in preparation The UCAC2 Bright Star Supplement
(End) Sean Urban [USNO, USA] 12-Mar-2004
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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