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I/172 International Reference Stars (IRS) (Corbin 1991)
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International Reference Stars (IRS)
Corbin T.E., Warren Jr. W.H.
<NASA, NSSDC 91-11 (1991)>
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ADC_Keywords: Positional data ; Proper motions
Description:
The IRS is an all-sky catalog of positions and proper motions that is
based on the AGK3R (Corbin 1977, 1978) in the Northern Hemisphere and
on the newly completed SRS (Smith et al. 1990) in the south. The data
for the 36027 stars of the IRS were compiled in B1950.0 FK4 and then
transformed to J2000.0 FK5.
The IRS was compiled by matching 122 meridian circle catalogs with the
AGK3R and SRS to provide the data base. Catalogs whose stars had been
observed using screens to minimize the magnitude equation and that
contained FK4 (Fricke and Kopff 1963) stars were used to form a
preliminary system. These catalogs were reduced to the FK4 by direct
comparison; the resulting positions and proper motions were then used
to reduce all of the other catalogs. Thus, the IRS is a differential
catalog compiled from 164,917 positions reduced to the FK4 system.
The IRS is divided into two parts. Part 1 contains the stars having
better observational histories and, therefore, more reliable positions
and proper motions. This part constitutes 81 percent of the catalog;
mean errors of the proper motions are 0.43 and 0.44 seconds of
arc/century (4.3 and 4.4 mas/yr) in right ascension and declination,
respectively. The stars in Part 2 have poor observational histories
and consist mostly of objects for which only two catalog positions in
one or both coordinates were available when the proper motions were
computed. Where accuracy is the primary consideration, it is best to
use only the stars in Part 1, while if the highest possible density is
desired, the two parts should be combined, as they are systematically
the same.
The data included are catalog part, IRS number, equatorial coordinates
(equinox, equator, epoch B1950.0 and J2000.0), centennial proper
motions (B1950.0 and J2000.0), original epochs, weights for right
ascension and declination, and reference data such as DM numbers (BD,
CD, CPD), AGK3 and CPC2 designations, and an IAU-recommended IRS
identifier (based on coordinates).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
irs.doc 80 420 ascii documentation
irs.tex 80 416 LaTeX documentation
adc.sty 78 68 Style file to process irs.tex
irs1.dat 192 29163 Part 1: more reliable positions and
proper motions
irs2.dat 192 6864 Part 2: stars with poor observational history
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See also:
I/15 : FK4 Catalogue (Fricke and Kopff, 1963)
I/72 : AGK3R Catalogue (Corbin, 1978)
I/85 : CPC2 (2nd Cape Photographic Catalogue 1950, Nicholson et al., 1984)
I/138 : SRS (Southern Reference Star catalogue, Smith, 1988)
I/149 : FK5 Catalogue (Fricke et al., 1988, Veroff. ARI 32)
For a high density of stars with accurate positions and proper motions
on FK5 system, see also the catalogues:
I/146 : PPM-North (Roeser and Bastian, 1988)
I/193 : PPM-South (Bastian and Roeser, 1993)
Byte-by-byte Description of file: irs1.dat, irs2.dat
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Bytes Format Units Label Explanations
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1 I1 --- PartNum [1,2] Catalog Part number, '1' or '2'
2- 7 I6 --- IRS *[1/76865]+ IRS sequential number
9- 10 I2 h RAh Hours RA, equinox=B1950, Epoch=B1950.0
11- 12 I2 min RAm Minutes RA, equinox, epoch B1950.0
13- 17 I5 ms RAms Seconds RA, equinox, epoch B1950.0
18 A1 --- DE- Sign Dec, equinox, epoch B1950.0
19- 20 I2 deg DEd Degrees Dec, equinox, epoch B1950.0
21- 22 I2 arcmin DEm Minutes Dec, equinox, epoch B1950.0
23- 26 I4 10mas DEcs Seconds Dec, equinox, epoch B1950.0
27- 29 I3 ms e_RAms ?Mean error in RA at original epoch
30- 32 I3 10mas e_DEcs ?Mean error in Dec at original epoch
33- 38 I6 0.01ms/yr pmRA RA proper motion, FK4 system
39- 45 I7 0.1mas/yr pmDE DE proper motion, FK4 system
46- 49 I4 0.01ms/yr e_pmRA ?Mean error on pmRA
51- 53 I3 0.1mas/yr e_pmDE ?Mean error on pmDE
54- 60 I7 0.001yr EpRA Original epoch of RA
(epoch of mean position)
61- 67 I7 0.001yr EpDE Original epoch of DE
(epoch of mean position)
68- 70 I3 --- o_RAms Number of positions in RA
71- 73 I3 --- o_DEcs Number of positions in DE
74- 77 I4 0.1 w_RAms Sum of the weights in RA
78- 81 I4 0.1 w_DEcs Sum of the weights in DE
82- 86 I5 0.01mag Pmag [520/1000] Photographic magnitude
87- 89 A3 --- SpType Spectral type
90- 97 A8 --- BD Bonner Durchmusterung number <I/122>
98-105 A8 --- CD Cordoba Durchmusterung number <I/114>
106-113 A8 --- CP Cape Photographic Durchmusterung <I/108>
114-120 A7 --- AGK3 AGK3 number <I/61>
121-126 A6 --- CPC2 Second Cape Photograpic Catalog <I/85>
127-150 A24 --- IRSJ *IRS number, IRS Jhhmmss.ssSddmmss.s
151-152 I2 h RA2000h *Hours RA, Equinox=J2000, Epoch=J2000
153-154 I2 min RA2000m *Minutes RA, equinox, epoch J2000.0
155-159 I5 ms RA2000ms *Seconds RA, equinox, epoch J2000.0
160-165 I6 0.01ms/yr pmRA2000 Centennial RA proper motion, J2000.0
166-171 I6 0.001yr EpRA-J2000 Original epoch - J2000.0 in RA
172 A1 --- DE2000- Sign Dec, equinox, epoch J2000.0
173-174 I2 deg DE2000d *Degrees Dec, equinox, epoch J2000.0
175-176 I2 arcmin DE2000m *Minutes Dec, equinox, epoch J2000.0
177-180 I4 10mas DE2000cs *Seconds Dec, equinox, epoch J2000.0
181-186 I6 0.1mas/yr pmDE2000 Centennial Dec proper motion, J2000.0
187-192 I6 0.001yr EpDE-J2000 Original epoch - J2000.0 in DE
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Note on IRS:
This number is between 1 and 29163 for the first part,
between 70001 and 76865 for Part 2.
Note on RA2000h, RA2000m, RA2000ms, DE2000d, DE2000m, DE2000cs:
The J2000 positions are given for equinox and epoch J2000.0 on the
system of FK5 after transformation of the B1950.0 values. The
transformation was done using the coefficients and software package of
Schwan (see Schwan 1988) and the algorithm given in the 1991
Astronomical Almanac (page B42) (foreshortening terms set to zero).
(See Section 3.1 of the documentation for additional details.)
Note on IRSJ:
This identifier is based upon the recommended IAU nomenclature (see
PASP, 102, 1444, 1990). The field consists of an origin in bytes
127-130 (IRS) and a coordinate specification in bytes 132-150 (byte
132 contains a "J" to indicate that the following coordinates are in
the Julian reference system and are for the year 2000.0, the standard
equinox designated for Julian system coordinates). Bytes 127 and 131
are blank for this catalog.
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References:
Corbin, T.E. 1977, The Proper-Motion System of the AGK3R (Ann Arbor,
University Microfilms, Inc.)
Corbin, T.E. 1978, in IAU Colloquium 48, Modern Astrometry, ed. F.V.
Prochazka and R.H. Tucker (Vienna, University Obs.), p. 505
(Catalog <I/72>)
Fricke, W., and Kopff, A. 1963, "Fourth Fundamental Katalog (FK4)", Veroeff.
Astron. Rechen-Inst. Heidelb. No. 10
(Catalog <I/15>)
Schwan, H., =1988A&A...198..363S
Smith, C.A., Corbin, T.E., Hughes, J.A., Jackson, E.S., Krutskaya, E.V.,
Polozhentsev, A.D., Polozhentsev, D.D., Yagudin, L.I., and Zverev, M.S.
1990, in IAU Symposium No. 141, Inertial Coordinate System on the Sky,
ed. J.H. Lieske and V.K. Abalakin (Dordrecht, Reidel), p.457
(Catalog <I/138>)
Historical Notes:
* 16-Apr-1991: the completed machine-readable IRS was transferred to
the Astronomical Data Center (NASA/Goddard)
* Catalogue distributed on the "Selected Astronomical Catalogs" Vol. 1
CD-ROM (1991), directory /astrom/irs
* 29-Nov-1995: ReadMe file standardized at CDS
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(End) Gail L. Schneider [SSDOO/ADC], Francois Ochsenbein [CDS] 29-Nov-1995