Space Motions of Low-Mass Stars. III. Arthur Upgren Wesleyan and Yale Universities, Middletown and New Haven, Connecticut 06457 aupgren@wesleyan.edu Julius Sperauskas Astronomical Observatory of the Vilnius University, Ciurlionio 29, Vilnius 2009, Lithuania julius.sperauskas@ff.vu.lt Richard P. Boyle Vatican Observatory Research Group, Steward Observatory, University of Arizona, Tucson, Arizona 85721 rboyle@as.arizona.edu Abstract Radial velocity observations are presented for 149 stars taken from the McCormick lists of dwarf K and M stars in a continuing program of radial velocities of faint nearby stars. The data will serve to derive a total stellar density of these kinds of stars in the solar neighborhood. These data were obtained with the spectrometer of the Vilnius University Observatory mounted on the 1.6m Kuiper Telescope of the Steward Observatory. Keywords: radial velocities, nearby stars 1 Introduction Two sources of lists of nearby dwarf stars complement each other. These are the compilations of stars found at the McCormick Observatory of the University of Virginia by Vyssotsky and his colleagues (Vyssotsky 1963, Weis and Upgren 1995 and references cited therein), and the Third Edition of the Catalog of Nearby Stars (CNS3) compiled by W. Gliese and H. Jahreiss at the Astronomisches Rechen-Institut in Heidelberg (Jahreiss 2000). Since each of the two surveys were limited in different ways, they can be used together to evaluate causes of systematic error in either of them. Such errors arise naturally from incompletenesses of the kind that are found in any stellar sample. The five McCormick star lists comprise almost 900 dwarf stars, most of which have spectral types between spectral types K3V and M2V with a few on either side of this range. These dwarf stars were detected and identified from objective prism plates, and thus form a magnitude-limited sample, with a limiting visual magnitude of about 11.5. The CNS3 includes all stars believed to be within 25 parsecs of the Sun, and is thus distance limited. For some time it has been known that magnitude limits impose the so-called Malmquist effect, in which stars of a given range in magnitude are always brighter on average than stars within a given distance range appropriate for the distance moduli of the stars. The correction depends mostly on the dispersion in the true absolute magnitude of the stars in the group; more stars brighter than the mean get counted than those that are fainter. The CNS3 stars are subject to the Lutz-Kelker effect (Lutz and Kelker 1973). This also requires a correction that depends mainly on the sizes of the standard errors in the determinations of the distances to the stars. Thus, since the volume of space considered increases with distance, more stars truly beyond a given distance limit appear within it due to the distance error, than nearer stars appear beyond it for the same reason. These two samples necessarily overlap each other considerably with many duplicates among their stars. They are about the only ones that can claim a high degree of completeness within their limits of the stars they include, and it would be useful to obtain complete kinematical information for all of them. They are also the two most representative of the stellar population forming the major component of the stellar mass component in the galactic disk. From astrometric observations (parallax and proper motion) the three spatial coordinates can be found, as well as their two first derivatives that lie in the plane of the sky at the tangent point for each star. To obtain a complete picture, the third derivative, the radial velocity, must also be known, and for faint stars, this is the information that has always proven hardest to obtain. Of the almost 900 McCormick stars, about 500 have a well determined radial velocity (one with an error of only 1 or 2 km/sec) and they are not randomly distributed within the entire group. The CNS3 stars include all of any kind within 25 pc, but since almost all stars of both groups have reliable photoelectric magnitudes and colors, the ones matching the properties of the McCormick stars can be identified. About a similar number and proportion of these also lack good radial velocities. It is our intention to complete the radial velocities of stars in both samples in order to evaluate the completeness of each, and to evaluate the Malmquist and Lutz-Kelker statistical biases inherent in each group (Lutz and Kelker 1973). This is the third list of radial velocities in a continuing program. The first list (Upgren and Caruso 1988) was made using the 1.5m reflector of the Harvard College Observatory, and the second (Upgren and Harlow 1996) used the 1.9m reflector of the David Dunlap Observatory. 2 Description of the Observations The radial velocity measurements were made with a CORAVEL-type spectrometer mounted on the Steward Observatory 1.6m Kuiper telescope at Mount Bigelow, Arizona on March 17 - 31, 2000. The spectrometer was built at the Vilnius University Observatory in 1998 and is based on principles of the photoelectric radial-velocity scanner developed by Griffin (1967). The principal optics of this instrument are assembled in accordance with the Littrow configuration in which a grating used in this configuration diffracts light along the incident light direction. As the camera-collimator an achromatic two-component cemented lens of focal ratio f/11 is used. An additional folding flat mirror is included to make the spectrometer more compact. The optical and mechanical design is almost identical to a design of the Coravel-type spectrometer built by Tokovinin (1987). A spectrum from 385 nm to 640 nm is dispersed by an echelle grating (75 gr/mm) over 25 orders. The dispersion is 0.14 nm/mm in the 62nd order, and 0.24 nm/mm in the 38th order. Cross dispersion is provided by a 22-grad flint prism in double pass mode. The size of the entrance slit of the spectrometer is 0.11x0.7 mm. The format of the scanned spectrum is 30 x 60 mm and for scanning a physical mask with 1800 slits is used. The transparent slits of the mask, which are the same size as the entrance slit, are made photographically on opaque film. The slits are centered on the positions of absorption lines of mostly neutral metals. This mask is valid for radial velocity measurements of stars of spectral types later than about F5. The cross-correlation profile shows an almost Gaussian shape dip. For a K2 III type star a FWHM of the cross-correlation dip is about 14 km/s and the contrast of the dip is 34 percent. The process of scanning is performed by moving the spectrum along the mask. The scanning speed is about 2 nm per sec. Light from the mask passes through a Fabry lens and is registered in a single photon counting mode by a bialkali (S11) photomultiplier Hamamatsu R647.The signal is read out every 8 ms. The zero point of radial velocity and the time-dependent drift of the spectrometer is determined by observations of several IAU radial velocity standards each night. Radial velocity values of the standard stars are taken from Udry et al. (1999). 3 Results A total of 153 radial velocity observations are presented in Table I for 149 stars in 139 stellar systems. The columns in the table represent the number of the star in the McCormick lists followed by the number in the Hipparcos Input Catalogue for all stars except V 506 for which the number in the Yale Parallax Catalogue is given. The remaining columns list the Julian date of observation, and the radial velocity and its standard error, both in kilometers per second. The errors were calculated according to Jasniewicz and Mayor (1988). Notes for a few of the stars are explained in the remarks at the end of the table. None of the stars appears to have a previously published radial velocity. Unlike the first two lists, this one concentrated on those without a known radial velocity determination, although the errors here duplicate in size those in the previous lists. As indicated in the table, a single observation was made for five unresolved binary stars; and, for ten others both components were observed separately. Only the brighter star was observed in two other systems. Two entries are given for four stars: V522, V527, V555, and V 697; in all four cases the differences between them is of the order of size of the errors. In no case do the observations suggest a probable but previously unrecognized binary star. The authors wish to thank Dr. Hartmut Jahreiss for providing information for some of the stars and The International Astronomical Union, through Commission 38, for travel support. We wish also to thank the Steward Observatory for the use of the telescope and the Vatican Observatory and the Jesuit community in Tucson for hospitality. References Griffin R.F. 1967, ApJ,148,465 Jahreiss, H. 2000, www.ari.uni-heidelberg.de/aricns/ (CNS3). Jasniewicz, G. and Mayor, M. 1988, Astron.Astrophys. 203, 329. Lutz, T.E. and Kelker, D.H. 1973, PASP 85, 573 Tokovinin A.A. 1987, AZh,64,196 Udry S., Mayor M., Maurice E., Andersen J., Imbert M., Lindgren H., Mermilliod J.-C., Nordstrom B., Prevot L. 1999, in Precise Stellar Radial Velocities (IAU Coll. No 170), J.B. Hearnshaw and C.D. Scarfe, eds. (ASP Conference Series No 185, p.383). Upgren, A.R. and Caruso, J.R. 1988, AJ 96, 719. Upgren, A.R. and Harlow, J.J.B. 1996, PASP 108, 64. Vyssotsky, A.N. 1963, in Stars and Stellar Systems, Vol III, Basic Astronomical Data, K. Aa. Strand, ed., p. 192. Weis, E.W. and Upgren, A.R. 1963, AJ 109, 812. Table I. Individual Radial Velocities of McCormick stars Star HIP JD+2400000 RV km/s s.e.km/s Notes V 248AB 36620 51622.656 17.2 0.7 V 255 42392 51622.707 11.6 0.7 V 263A 42392 51622.723 11.8 0.7 V 263B 42392 51622.719 10.4 0.8 V 269 46662 51622.730 -50.7 0.7 V 272AB 47386 51622.738 -5.5 0.7 V 279 54519 51623.754 -17.1 0.7 V 280 54559 51623.762 -14.1 0.8 V 288 58083 51622.793 6.5 0.7 V 310 67501 51622.840 6.1 0.7 V 311 68447 51622.848 -47.4 0.7 V 472 29865 51622.648 5.0 0.7 V 481 33322 51622.680 -37.7 0.7 V 483 33368 51622.672 29.0 0.7 V 484 33805 51622.688 19.8 0.9 V 486 34034 51622.664 -0.0 0.7 V 491 35504 51622.695 24.4 0.7 V 495 36037 51627.629 11.2 0.8 V 500 37246 51626.656 -32.2 0.8 V 502 37488 51627.637 24.4 0.7 V 504 37412 51626.664 90.2 0.7 V 506 1841.01 51627.641 -22.9 0.7 V 508 38619 51626.645 -24.1 0.7 V 509 38492 51626.676 56.5 0.8 V 513 39821 51627.680 -40.1 0.7 V 514 40089 51627.648 10.5 0.8 V 515 40131 51627.652 -42.3 0.7 V 517 40140 51627.672 22.9 0.7 V 519 40839 51627.688 47.9 0.7 V 522 41277 51627.691 24.1 0.7 'vsini' V 522 41277 51633.656 24.1 0.8 V 523 41431 51626.684 25.3 0.8 V 524 41626 51627.664 -67.6 0.7 V 525 41663 51628.656 -21.7 0.8 V 526 41662 51627.699 2.2 0.7 V 527 41889 51626.695 27.0 2.3 '?' V 527 41889 51626.730 24.1 4.1 '?' V 530 42783 51627.715 -0.6 0.7 V 535 43363 51627.703 31.0 0.7 V 536 43516 51627.711 -24.1 0.7 V 539 44926 51627.734 7.6 0.7 V 547AB 46671 51627.742 -2.9 0.8 V 553 47735 51628.660 -15.6 0.8 V 554 47899 51628.668 6.9 0.8 V 555 47972 51628.688 70.7 1.1 'vsini' V 555 47972 51633.695 71.2 1.0 'vsini' V 556 48016 51628.695 31.3 0.8 V 561 49046 51627.750 -11.3 0.8 V 563 49067 51628.711 53.0 0.8 V 572 50375 51627.758 14.1 0.8 V 576 50776 51627.762 -7.0 0.7 V 577 50773 51627.766 -16.5 0.7 V 581 51208 51628.723 48.1 0.8 V 582 51443 51628.742 31.6 0.7 V 584 51571 51628.727 -37.1 0.9 V 585AB 52008 51627.773 5.8 0.7 V 586 52021 51628.734 1.8 0.8 V 589 53123 51628.750 -46.8 0.7 V 590 53189 51627.777 -7.8 0.7 V 592 53383 51627.785 8.1 0.7 V 593 53637 51626.754 0.2 0.7 V 595 54094 51626.762 -21.0 0.7 V 596 54002 51627.789 -9.1 0.6 V 598 54100 51627.797 13.7 0.7 V 606 55077 51627.813 9.5 0.7 V 610 55922 51627.801 -11.5 0.7 V 611 56092 51622.820 23.9 0.7 V 620A 57731 51627.836 7.9 0.7 V 620B 57731 51627.840 7.9 0.7 V 621A 57857 51627.816 -22.2 0.8 V 621B 57857 51627.820 -16.1 2.4 V 623A 58056 51628.793 7.8 0.9 V 623B 58056 51628.797 5.2 0.8 V 624A 58197 51628.777 1.7 0.8 V 624B 58197 51628.781 0.5 0.9 'B+A?' V 625 58212 51628.789 4.2 0.8 V 626 58289 51622.797 -6.2 0.7 V 627AB 58412 51632.781 -7.0 0.8 V 628 58770 51622.828 3.0 0.7 V 629 58869 51622.813 -5.7 0.8 V 630 58872 51622.805 22.9 0.7 V 632 58945 51628.801 -5.8 0.8 V 634 59247 51628.809 6.0 0.8 V 639 59754 51628.816 2.9 0.8 V 642 59846 51632.789 -6.1 0.8 V 643 59905 51628.824 -3.4 0.8 V 646 60115 51632.801 83.8 1.0 V 647 60186 51627.848 -8.4 0.8 V 648 60265 51627.852 -6.0 0.8 V 650 60346 51627.859 -27.9 0.7 V 651 60336 51632.809 -9.0 0.7 V 652 60438 51628.840 56.7 1.2 'vsini' V 653 60433 51627.867 -44.7 0.7 V 654 60448 51627.883 -29.0 0.9 V 656 60633 51627.891 12.8 0.7 V 657 60704 51632.813 -7.1 0.8 V 661 61043 51628.875 -26.2 0.8 V 663 61128 51628.883 43.6 0.8 V 664 61289 51628.887 -0.3 0.8 V 665 61276 51632.859 -0.8 0.7 V 667A 61633 51632.848 -11.4 0.8 V 667B 61633 51632.840 -11.3 0.8 V 668 61704 51632.820 -14.1 0.9 V 669 61750 51632.828 7.0 0.8 V 672 62160 51632.867 22.9 0.8 V 673A 62201 51632.855 -1.9 0.7 V 673B 62201 51632.855 -1.9 0.8 'B+A?' V 674 62454 51627.898 -10.4 0.8 V 678 62779 51627.902 12.5 0.8 V 679 62755 51632.832 -7.8 0.8 V 680 62859 51627.910 -7.1 0.7 V 687 64836 51627.918 -4.4 0.8 V 690 65706 51628.926 3.3 0.8 V 697 66828 51629.898 -20.7 1.3 '?' V 697 66828 51630.891 -20.6 0.7 V 707 68745 51628.945 -12.4 0.8 V 708A 68889 51628.957 -58.1 0.8 V 708B 68889 51628.961 -58.4 1.0 'B+A?' V 709A 69050 51628.969 0.2 0.9 V 709B 69050 51628.973 0.4 0.8 'New V 710 69311 51628.980 -19.8 0.7 V 712 69446 51628.996 1.8 0.8 V 717 70317 51630.898 -21.6 0.7 V 724A 72504 51630.941 -46.7 0.7 'B V 725 72753 51630.914 -14.4 0.7 V 727 73085 51630.926 -54.0 0.8 V 728 73194 51630.906 42.8 0.8 V 729 73121 51630.938 -50.8 0.7 V 730 73258 51627.945 15.9 0.8 V 732 73183 51630.949 -28.8 0.9 'vsini' V 735 74331 51627.961 -14.5 0.8 V 737 74682 51627.953 38.3 0.7 V 738A 74891 51627.969 -17.6 0.7 V 738B 74891 51627.973 -15.8 1.1 V 741 75337 51627.980 -46.3 0.7 V 745 76042 51630.973 14.0 0.7 V 747 76374 51627.988 -27.5 0.8 V 749 77269 51628.008 -46.0 0.8 V 750 77451 51628.012 -50.8 0.8 V 752 78074 51628.020 -52.9 0.7 V 755 78184 51628.027 -43.9 0.7 V 756 78356 51628.023 -13.5 0.7 V 757 78678 51623.043 -43.9 0.7 V 764 80539 51623.008 -53.3 0.7 V 768 80751 51628.035 -30.4 0.7 V 769 81030 51629.004 -78.2 0.8 V 773 81998 51629.023 -26.6 0.8 V 775 82169 51629.012 20.1 0.8 V 777 82030 51629.035 -13.0 0.8 V 778 82370 51623.020 -29.8 0.7 V 780A 82206 51630.988 -38.7 0.7 'B V 784 82844 51623.039 -33.0 0.7 V 793 84992 51623.027 -57.1 0.6 Remarks for individual stars. 'B unseen' - B component was unseen in the field of the telescope. 'B+A?' - the light of the component B might be contaminated with the scattered light of the brighter component A on the slit of the spectrograph. 'vsini' - the width of the cross-correlation function indicates that these stars rotate faster than K -M dwarfs ( vsini> 20 km/s).