proper motions of hipparcos stars in two plate areas
TRANSCRIPT
CHINESE ASTRONOMY AND ASTROPHYSICS
PERGAMON Chinese Astronomy and Astrophysics 24 (2000) 257-264
Proper motions of Hipparcos
in two plate areas * t
stars
WANG Shu-he TANG Zheng-hong JIN Wen-jing Shanghai Observatory, Chinese Academy of Sciences, Shanghai 200030
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012
Abstract Using the ACT reference catalogue as preliminary reference we have
reduced 31 exposures on 15 plates in two areas taken with the 40-cm refractor
of our Observatory. Using the central overlapping technique and an iterative
procedure we have derived high-precision positions and proper motions for 54
stars, including 16 Hipparcos stars. For the latter, the mean standard errors. in
right ascension and declination, are 0.70 and 0.59mas/yr in proper motion, and
10.5 and 7.5 mas in position.
Key words: astrometry-proper motion-Hipparcos stars
1. INTRODUCTION
The successful completion of the HIPPARCOS Program in the 1990s marked a revolutionary
achievement in astrometry. The HIPPARCOS catalogue 111, however, is only a reference
system composed mainly of stars brighter than magnitude 9, and the satellite’s observation
only spanned a little over 3 years. The problem common to available catalogues with limiting
magnitudes fainter than magnitude 12 is this: either the limiting magnitude is not faint
enough, or the precision of positions and proper motions is not high enough, or the star
density is not high enough. The IAU has established a Working Group of International
Celestial Reference System (ICRS) t o replace the original Working Group of Reference
Frame (WGRF); it has 6 tasks12~31: maintenance and extension of the ICRS, densification in
optics, ties with previous and new catalogues, link to the dynamical system, computational
consequences, and relation with the International Earth Rotation Service (IERS). These
have been hot points of research in reference to three specific problems of the HIPPARCOS
t Supported by National Natural Science Foundation, Chinese Academy of Sciences and National
Scaling-the-Heights Program
Received 1998-09-07; revised version 1998-12-10
* A translation of Acla Astton. Sin. Vol. 40, No. 4, pp. 351-359, 1999
0275-1062/00/$ - see front matter @ 2000 Elsevier Science B. V. All rights reserved.
PII: SO275-1062(00)00050-3
258 WANG Shu-he et al. / Chinese Astronomy and Astrophysics 24 (2000) 257.264
catalogue, namely, improving the precision of proper motions so as to maintain the system
for a long time, extending to fainter magnitudes to include more faint objects and linking to
the extragalactic reference system to approximate more closely with a quasi-initial system.
The Shanghai astronomical Observatory has a long history of photographic astrometry.
Since 1901, the 40-cm refractor (f=6895 mm) at She-Shan Station of Shanghai Astronomical
Observatory has made observations; now, after nearly a century, it has accumulated some
10 thousand photographs on plates 141. The plate size is 30 cm x 24cm (2.5’ x2’). There
are about 4000 plates in stock, and 3435 of these have known plate centers and belong
to 764 different sky areas. In these areas, there are about 10,000 HIPPARCOS stars, so,
making full use of these plates, especially those including external galaxies, will be a valuable
contribution to the maintenance and extension of the HIPPARCOS catalogue. This paper
is part of the results of our long research program “Maintenance and Extension of the
HIPPARCOS Catalogue with She-Shan Plates”.
Using ACT151 Reference Catalogue as a preliminary reference catalogue, plates of two
sky areas taken with the 40-cm refractor were reduced by means of the central overlapping
technique, and high precision positions and proper motions of HIPPARCOS stars and field
stars in the two areas obtained.
2. ACT REFERENCE CATALOGUE
The U.S. Naval Observatory has completed the compilation of the ACT Reference Catalog
in 1997.9, its positions are combined from new reductions of the Astrographic Catalogue
(AC 2000) and Tycho catalogue, the later is part of the results of HIPPARCOS satellite.
The Tycho catalogue contains 1,058,322 stars, its astrometric precision is 25ma.s (for all
stars), 7mas (for those brighter than mag 9). The ACT catalogue contains 988,758 stars
covering the entire sky, with about 25 stars per square degree. The positions and proper
motions of ACT are on the HIPPARCOS System (52000.0) for epoch J2000.0, and the mean
precision is 22.5 mas for position, and 2.2 mas/yr for proper motion. It seems that the ACT
catalogue is better than those often used as reference catalogues such as AGK3, PPM and
ACRS. Another purpose of this paper is to check the precision of the ACT with actual data
reduction.
3. OBSERVATIONAL DATA
The photographic plates used in this paper are listed in Table 1. Each exposure is regarded
as one observation. All the plates were digitally measured with the PDS-1OlOMS micro-
densitometer of Purple Mountain Observatory, and the precision of star image measurement
is better than lpm. For detailed description of the measurement we refer to the references
[7-91.
4. CHOOSING MODEL OF PLATE CONSTANTS
Considering that the stars are distributed in quite a large field (2Ox1.5’) and that their
WANG Shu-he et al. / Chinese Astronomy and Astrophysics 24 fZOO0) 257-264
magnitudes range from 7.8 to 12.5, we first used both a 14parameter model
parameter model (eqn. (1)) as tests, and found the latter to be the better one.
259
and the 20-
Cij = aijxij + a2jYij + a3j + a4jXtj + QjXijyij + a6jY:j + aTjXij(Xfj + yfj)
+asj% + a9jmiXij + CLlojCi
Tij = hjxij + b2jYij + b3j + b4jXfj + b5j xijyij + bgjy~j + bTjxij( xF~ + $j )
+bsjmi + bgjmixij + blojci
here, <ij and qij are the standard coordinates of the i-th star in the j-th exposure, xcij
and yij are the corresponding measured coordinates, aij...oiej, blj_..bloj are the 20 plate
constants, m is the B magnitude, and c(= B - V) is the color index, both are taken from the
ACT catalogue, and are derived from HIPPARCOS data and standardized to the Johnson
standard photometry system.
In this preliminary treatment as well in the following reduction, the weight of the star
image is computed as in Ref. [lo].
Table 1 Observational Material
NO. Plate No. Observational Date Exposure (min) Observer
1 G56063 1956-11-25 60 ZHAI Shu-wen
2 G57037 1957-11-17 60 ZHANG Xia-shun
3 G57047 1957-12-15 60 ZHAI Shu-wen
4 RS85060 1985-12-15 70 CHU Zong-yuan
5 MS5063 1985-12-16 75 CHU Zong-yuan
6 RS85069 1985-12-19 15, 15, 15 CHU Zong-yuan
7 RS86003 1986-01-04 15, 15, 15 XU Tong-qi
8 RS86009 1986-01-05 15, 15, 15 XU Tong-qi
9 RS86019 1986-01-07 15, 15, 15 CHU Zong-yuan
1 G58020 1958-05-26 20 HU Kun-lin
2 G64064 1964-08-07 15 GUO Qi-wei
3 G85007 198546-19 5, 5, 5 CHU Zong-yuan
4 G85019 1985-08-l 5 5, 5, 5 CHU Zong-yuan
5 G85022 1985-08-06 5, 5, 5 CHU Zong-yuan
6 G85025 1985-08-09 7, 7, 7 CHU Zong-yuan
5. REDUCTION
In this paper, the ACT Reference Catalogue was used as a preliminary reference catalogue,
and the central overlapping technique and an iterative procedure were used in the reduction,
the relevant equations are the same as in Ref. [lo].
The standard coordinate system used in the reduction is J2000.0 mean equator coordi-
nate system. The positions of the preliminary reference stars were transferred from J2000.0
to the plate epoch, by adding the correction for the proper motion, to obtain the standard
frame of the plate to be referred to in the first round. At the same time, the positions of the
preliminary reference stars were also corrected for their proper motions between 32000.0
260 WANG Shu-he et al. / Chinese Astmnomy and Astrophysics 24 (2000) 257~264
1 15216
2 15437
3 15494
4 15496
5 15544
6 15731
7 15791
8 15831
9 1431966
10 1431967
11 1432046
12 1432178
13 1432289
14 1432302
15 1432326
16 1432400
17 1432438
18 1432509
19 1432513
20 1432535
21 143254-l
22 1432702
23 1432728
24 1432736
25 1432754
26 1432834
27 1432867
28 1432872
29 1432910
NO. (I 0. 6 08 f% 0, pa aa T.x Tdr
1900 +
89.13
86.89
86.30
86.61
90.16
90.01
90.34
90.57
85.56
81.23
85.77
81.01
82.51
81.95
85.64
85.83
88.32
81.09
82.91
81.22
80.83
86.77
81.75
8X.88
82.78
89.61
83.83
80. RJ 85.74
h m s . I ”
3 16 08.50313 52 + 41 51 36.8842 42
3 18 57.15936 67 +41 11 10.8369 69
3 19 39.22016 180 +40 58 42.6276 95
3 19 41.14401 68 +42 10 33.8959 61
3 20 17.28997 38 +41 53 49.9567 55
3 22 39.73493 65 +41 55 34.5989 43
3 23 30.59719 58 + 41 12 24.9448 74
3 23 55.55156 68 +41 20 13.3548 78
3 15 59.81386 113 +40 59 58.5480 76
3 15 59.88190 173 +42 16 13.5700 198
3 16 45.12255 134 +42 13 10.0194 94
3 18 01.74778 172 +40 41 57.9925 119
3 18 56.09920 112 +42 05 29.2583 119
3 19 01.94996 159 +41 03 26.7126 237
3 19 16.62328 131 +40 56 42.3817 64
3 19 52.78895 56 +42 12 31.0378 130
3 20 15.10473 74 + 42 13 26.5267 124
3 20 42.36495 184 +40 45 38.0473 116
3 20 47.13620 125 + 42 13 19.1475 122
3 20 56.71178 114 +41 05 58.8969 90
3 21 00.00874 268 +41 05 44.5602 124
3 22 19.70284 73 +42 10 02.0535 63
3 22 33.109Sh 59 + 31 25 33.3848 107
3 22 36.74056 83 +41 41 30.3189 88
3 22 46.34602 94 +41 30 27.9283 122
3 23 26.56738 55 + 41 42 30.8435 81
3 23 46.52907 63 +41 07 11.3914 95
3 23 49.30358 138 +41 23 47.5337 131
3 24 08.26054 75 + 40 58 07.5748 154
“/yr -0.00253 44
- 0.00376 55
0.00734 129
0.02053 45
0.01365 38
0.02441 69
0.01196 61
-0.00175 73
-0.00658 90
-0.01353 70
-0.00345 74
0.04171 83
0.01545 62
-0.00229 81
-0.00884 100
0.01032 35
0.03188 61
-0.01702 94
0.00005 58
0.04199 58
-0.00325 126
-0.00058 63
0.0182.1 15 -.
0.00127 68
0.00200 43
0.00354 58
0.00032 31
0.01234 69
0.01272 57
“/yr
-0.01553 32
-0.00511 43
-0.01257 52
-0.00737 33
-0.01485 46
-0.03857 35
-0.02664 64
-0.00155 71
-0.00141 38
-0.00646 88
-0.00879 54
-0.12349 54
-0.00655 52
0.00319 110
-0.00192 33
-0.00900 75
-0.02779 79
0.00598 51
0.00158 54
-0.02827 39
-0.00553 51
-0.02549 35
0 OO’J50 47
-0.00019 61
-0.02001 57
- 0.00325 62
- 0.005 I8 48
-0.017OJ 57
-0.01999 79
1900 +
89.08
88.88
88.20
88.86
90.77
90.75
90.91
90.95
88.41
81.84
87.65
79.52
84.34
83.81
88.03
88.48
89.94
82.01
85.22
82.37
81.53
89.14
83.16
90.11
81.63
90.60
85.95
81.78
88.45
Table 2 Results of Reduction of 16 HIPPARCOS Stars and 38 Field Stars (ACT Star)
in Two Areas
30 1432912
1 88595
2 88721
3 88730
4 88760
5 88876
6 88884
7 88932
8 89071
9 2798247
10 2798872
11 2798959
12 2798984
13 2798990
14 2799052
15 2799212
16 2799236
17 2799551
18 2799562
19 2800155
20 2800161
21 2800235
22 2800622
23 2800628 24 2801692
3 24 08.84812 29 +40 43 08.2715 141 -0.00411 23 -0.00490 88 89.54 87.10
18 05 22.72106 35 -21 4023.4548 108 -0.06137 39 -0.12914 97 90.02 90.20
18 06 46.12010 94 -22 27 52.3941 48 0.00164 83 0.00047 37 8X.28 89.05
1806 51.19763 110 -21 30 19.1994 86 0.00363 138 -0.00104 81 90.12 90.41
1807 11.34790 115 -21 26 38.2366 70 0.00138 175 -0.00960 77 91.05 91.12
18 08 38.57827 68 -21 26 58.4563 77 -0.00412 78 -0.00766 61 89.54 89.75
18 08 44.91245 II5 -22 09 38.4797 85 -0.00146 137 -0.00503 79 89.98 90.29
18 09 12.16651 137 -22 11 01.4753 124 -0.00997 91 -0.09493 67 83.22 84.22
18 10 44.13652 47 - 22 14 22.9825 88 -0.00452 53 -0.00698 72 89.37 89.51
18 05 13.65165 129 -22 24 35.4464 210 -0.00480 66 -0.01401 102 80.88 83.58
18 05 50.99733 82 - 22 12 16.0792 67 -0.00292 83 -0.00081 54 88.57 89.23
18 06 05.63857 79 - 22 06 58.9918 69 -0.00012 72 -0.00293 44 88.07 88.80
18 06 10.40892 85 -21 27 42.2301 56 0.00231 90 -0.00411 47 89.01 89.49
18 06 11.09697 96 - 22 27 34.9771 126 -0.00433 75 -0.00266 86 85.83 87.72
18 06 22.96120 108 -22 43 16.4534 182 -0.00015 75 0.00285 102 83.93 85.20
18 06 49.52924 71 - 22 02 47.8883 42 -0.00885 74 -0.00758 35 88.86 89.57
18 06 52.45512 143 - 22 35 53.6007 237 -0.00068 82 -0.00616 121 81.16 83.30
18 07 38.22705 60 - 22 06 57.4601 108 -0.00219 59 -0.00209 85 88.44 89. 15
18 07 39.86621 76 - 22 04 37.7680 72 -0.02341 69 -0.02352 54 87.63 88.76
18 08 55.63322 48 -21 24 08.8958 105 0.00211 36 -0.00398 74 86.52 87.90
18 08 56.41370 83 - 22 10 34.2077 132 -0.00030 74 -0.00487 102 88.48 88.91
18 09 04.80647 97 -21 24 24.8047 110 0.00067 75 -0.00150 70 85.69 86.81
18 09 48.39131 56 -22 07 23.8335 86 -0.01309 40 -0.00449 48 85.37 85.53
18 09 48.61312 61 - 22 03 22.5520 103 0.00110 54 -0.00019 70 87.75 88.05 18 11 43.03962 66 - 22 06 16.7789 145 0.00076 70 -0.00369 98 88.78 88.62
WANG Shu-he et al. / Chinese Astronomy and Astrophysics 24 (2000) .257-264 261
and the epoch given in the catalogue, resulting in the preliminary positions used in the
reduction of proper motions. To each star that has been reduced, its standard coordinates
given by the reference catalogue were adjusted for position and proper motion. The adjusted
positions and proper motions then define a new catalogue. This new catalogue would then
be used as the new initial reference in the next round of the reduction. With the new stan-
dard coordinates and the new values of the weights. the positions and proper motions were
solved again. This iterative procedure would continue until there was no further noticeable
improvement in the precision of the positions and proper motions. The final root-mean-
square values are 12, 4, 5 and 4 units in the last decimal in Table 2, and the maximum
errors are 35, 8, 6 and 7 units.
6. RESULTS AND EXTERNAL COMPARISON
The results of positions and proper motions of the stars in the two sky areas are listed in
Table 2, where column 1 gives the serial number of the star in this paper, column 2 is its
serial number in the HIPPARCOS Catalogue (5 digits) or the AC2000 Catalogue (7 digits),
columns 3 and 5 are its right ascension and declination referred to the equinox and epoch
of 52000.0; columns 7 and 9, its proper motions in right ascension and declination, while
columns 4, 6, 8 and 10 are the corresponding standard errors, in units of the last decimal
of the quantities concerned; lastly, columns 11 and 12 are the central epochs for the right
ascension and declination, being the weighted means of the observational epochs of all the
plates used. Since the ACT catalogue is regarded as one observation, and its precision is
high, the epochs given are near the epoch of the ACT, i.e. J1991.25.
There are 16 HIPPARCOS stars in Table 2; for these, the mean internal errors are
10.5 mas and 7.5 mas in right ascension and declination and 0.70 mas/yr and 0.59 mas/yr in
the two components of proper motion. The corresponding mean errors for all the 54 stars
in the two sky areas are 11.7 and 10.5mas, and 0.59 and 0.64mas/yr.
Comparison of positions and proper motions of stars common to different catalogues
will bring out the differences between catalogues. Table 3 gives the difference between our
results and the ACT, HIPPARCOS and PPM catalogues. It should be pointed out that,
here, the rms here refers to the difference between the catalogues and does not have its
usual meaning. A comparison between the HIPPARCOS and ACT is also given for the
mean epoch of the two, J1991.25.
The differences in position and proper motion for stars common to our list and the
ACT, HIPPARCOS and PPM catalogues and between the first two named catalogues are
displayed in Fig. 1 (Sky Area 1) and Fig;2 (Sky Area 2). In the panels, the circles mark the
positions of the stars given in this paper and the rays mark the vector differences (differences
in position, in the left panels; in proper motion, the right panels), on the scale shown at
bottom left of each panel.
It can be seen from the figures and Table 3 that the differences between our results
and the ACT and HIPPARCOS catalogues in Sky Area 1 (Fig. 1) are small and with no
obvious systematic trends; in Sky Area 2 (Fig. 2) the differences are again small, but they
are obviously systematic. The positions of AC2000 were computed from AC plates which
were observed by 22 different observatories around the world; this fact may have caused
Dec
lin
atio
n
(dea
ree)
$
40.5
41
41
.5
42
42.5
$
WANG Shu-he et al. / Chinese Astronomy and Astrophysics 24 (2000) 257-264 263
the positional differences between our results and ACT
28 1
+ 1 I
z the scale:O’.% ’ I 271 271.5 272 272.5 273
the positional differences between our results and HIP
2c ,
In
XT;;; -T-
P-- s
.E,q::- 2 ’ 2 72 -\ 2,
i-4 ’ the scale:O’.Z
.I 271.5 272 272.5 273
the positional differences between our results and PPM
2e 1
&
I 4
z the scale:l” ’ 1 271 271.5 272 272.5 273
the positional differences between AcTand RIP
r ;;_ 28 I
l . k-J
i ;- l . m o pr: l
3c-4_ g?, .r(
l -. ii?: .
2:
.
i ’ .
Tb---+ the seele:oY?
271.5 272 272.5 273 Right Ascension(degree)
the differences in proper notion between our results and ACT
1 2b
1 4 ; the scale:10 mas/yr
’ 271 271.5 272 272.5 273
t.he differences in proper motion betrwn our rrsults and HIP
271.5 272 272.5 273
the differences in proper motion between
[‘2f our resuits- and ppy
I
the differences in proper motion bet-em ACTand HIP
O- ’ the scale:10 ms/yr
271.5 272 272.5 273 Right Ascension(degree)
Fig. 2 The differences in positions and proper motions between our results and ACT, HIP, PPM
(Sky area 2)
264 WANG Shu-he et al. / Chinese Astronomy and Astrophysics 24 (2000) 257-264
Table 3.1 Comparison with other Catalogues (Sky Area 1)
This Paper ACT This Paper - HIP This Paper - PPM ACT-HIP Number of ~~rnnlc~n stars 30 8 30 11 Aa cos 6 (mu) -1.8 f 51.1 15.9 f 26.6 98.1 f 312.5 1.8 f 9.9 A6 (mas) -2.4 f 26.6 -0.4 f 9.0 -173.2 f 313.6 4.5 f 12.7 Ap cos 6 (mas/yr) -1.95 f 5.18 -2.56 f 3.58 0.01 f 6.80 -0.12 f 2.59 Ap’ (mas/yr) -0.23 f 2.12 1.15 f 1.69 -2.07 f 4.63 1.16 f 1.60
Table 3.2 Comparison with other Catalogues (Sky Area 2)
This PaDW - ACT This Paoer - HIP This PaDer - PPM ACT-HIP
Number of conunon stars 24 8 26 12
Aa cos S (mas) -54.2 f 59.9 -63.9 f 72.8 -97.9 f 167.6 -1.6 f 8.3
A6 (ma) 3.0 i 9.7 4.9 f a.7 278.6 f 342.2 1.8 f 6.7
A&r cos 6 (mas/yr) 1.33 f 4.18 -0.55 i 3.04 1.78 f 4.64 -1.76 f 5.53
Ap’ (mas/yr) -0.34 f 1.55 -2.70 f 3.78 2.72 f 6.74 -0.41 f 3.35
some systematic differences in Sky Area 2 (declination about -22’). The differences between
our results and the PPM catalogue are large in both areas, and are obviously systematic.
This is probably due to the fact that the mean error of the PPM proper motions is quite
large (4.2mas/yr) and its mean epoch is 1931. From the figures it can also be noted that
the differences between the HIPPARCOS and ACT are not as small as might be expected,
especially in the proper motions: some are larger than 2mas/yr though the average is below
l.Bmas/yr. Although the results of this paper are based only on two sky areas, it shows
that the proper motions of HIPPARCOS and ACT still need to be checked further.
ACKNOWLEDGEMENT We thank the following colleagues who, over the years, took
the plates used in this work: ZHANG Xiao-shun, ZHAI Shu-wen, XU Tong-qi, HU Kun-lin.
GUO Qi-wei and CHU Zong-yuan. We also thank the colleagues in the PDS Team of Purple
Mountain Observatory for their help.
4
5
6
7
8
9
10
References
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Mignard F., The Circular 1 of IAU WGRF, Private communication, 1998
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Tang Zheng-hong et d., Annals of Shanghai Observatory, 1997, 18: 61-68
Urban S. E., Corbin T. E., Wycoff G. L., ACT Reference Catalogue, 1997
USNO, The AC2000, 1997
WANG Jia-ji et al., AnnaIs of Shanghai Observatory, 1988, 9, 38
WANG Jia-ji et al., Annals of Shanghai Observatory, 1992, 13, 62
WANG Jia-ji et al., Annals of Shanghai Observatory, 1990, 11, 67
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