I/178 CATALOGUE OF PROPER MOTIONS IN NGC 7209 ================================================================================ I.Platais Yale University, Department of Astronomy P.O. Box 6666 New Haven, CT 06511 U.S.A. 1. Introduction This is a catalogue of proper motions in and around the open cluster NGC 7209 (C2203+462) which is a representative of the poorly-populated open cluster class. Relative proper motions of 4290 stars in a 120'-diameter circle around the cluster have been determined from the PDS measurements of 12 Pulkovo normal astrograph plates (scale 59.57 "/mm) and 1 plate from the Tashkent normal astrograph. The catalogue of proper motions is complete down to mpg=15.1m, the limiting value is 15.6m. The average standard error of the catalogue proper motions in the highest weight group (the star is present on all or nearly all plate pairs) varies from 0.6 milliarcseconds per year (mas/yr) for stars with mpg<14.5m to 0.75 mas/yr for the fainter stars. In order to derive the standard error of a star from the lower weight group, a unit weight error of 2.8 mas/yr and the appropriate weights from Table I must be used over the plate pairs used in the determination of the star's proper motion, as given in the Catalogue. For the faint stars located far from the field centre, an additional factor proportional to the accuracy degradation should be applied. Table I. Assigned weights. -------------------------------------------------------------------- | Pair No. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | |----------|-------|-------|-------|-------|-------|-------|-------| | Weight | 4.6 | 4.6 | 4.6 | 2.8 | 1.0 | 2.8 | 1.7 | ---------------------------------------------------------- --------- Example: For the star No. 27 the weighted standard error of the proper motion is as follows: 2.8/SQRT(4.6+1.0)*1.3=1.5 mas/yr. The degradation factor 1.3 is derived from the accuracy estimate for the faint stars located at the edge of the field. More detailed information on measured plates,standard errors, assigned weights, membership probabilities, etc. is given in Platais (1991). The membership probabilities were calculated assuming that on the vector- point diagram the distribution of field stars is flat enough within a limited area around the centroid of cluster member proper motion distribution. A good separation of field and cluster stars is achieved. 2. Tape content The catalogue of proper motions consists of 2 files. File 1. Description of the catalogue File 2. Catalogue of proper motions in NGC 7209. Record length: 80 bytes. For data presentation the first 63 bytes are used, the remaining 17 bytes are blanks. Number of records: 4290. The length of each physical block is 800 bytes. A brief description of the data fields is given below. For each field is listed: mnemonic abbreviation of the data item; the position of the data in File 2 (first - last byte or column number); its FORTRAN format specification; a short description of the data item. -------------------------------------------------------------------------------- Name Bytes Format Explanation -------------------------------------------------------------------------------- NO. 1 - 4 I4 Sequential number of the star. NL 5 - 9 I5 Identification number from Lavdovsky (1961). NSW 10 - 13 I4 Identification number after van Schewick et al. (1966). The original numbers from van Schewick's et al. Katalog IV are increased by adding one hundred. NM 14 - 17 I4 The number from the Maevers (1940). If the Maevers number has a prefix "K", it is replaced by "2". X 19 - 27 F9.4 Rectangular coordinates in millimeters derived from Y 28 - 36 F9.4 the PDS measurements of the second epoch plate #15318 (epoch 1987.72; equatorial coordinates of the optical centre are: A = 22 hours 3 minutes and 29.6 seconds D= 46 degrees 14 minutes and 57 seconds (1950.0)). The origin of the rectangular X,Y-coordinates and the optical centre are matched. Also the X,Y-coordinate system is oriented closely with the equatorial system. MPG 37 - 42 F6.2 Photographic magnitude derived using the Maevers (1940) photographic magnitudes. An internal accuracy is not worse than 0.05 magnitude. MUX 43 - 47 I5 Relative proper motions given in 0.0001 "/year. The MUY 48 - 52 I5 proper motions are determined relative to the field stars of about mpg=14.0m. P 53 - 55 I3 Calculated membership probability in percent. PAIRS 57 - 63 A7 Designation of plate pairs used for the calculation of the catalogue proper motion. If the star is measured on all pairs this entry looks as follows: 1234567, otherwise the omitted pair number is replaced by a zero. -------------------------------------------------------------------------------- References Lavdovsky, V.V.: 1961, Trudy Pulkovo 73,5. Maevers, F.W.: 1940, Astron Nachr. 270, 201. Platais, I.: 1991, Astron. Astrophys. Suppl. 87, 577. van Schewich, H., Haase, H.S., Heidrich, G. and Nentwig, H.: 1966, Veroeff. Astron. Inst. Univ. Bonn No.74, 1. ================================================================================ (End) 25-Feb-1992