4C 4 2 . 83. THE ASTRONOMICAL JOURNAL VOLUME 83, NUMBER 3 MARCH 1978 ABSOLUTE SPECTRAL ENERGY DISTRIBUTIONS AND [Fe/H] VALUES OF METAL-POOR STARS AND GLOBULAR CLUSTERS 1978AJ Clark G. Christensen Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602 California Instititute of Technology, Pasadena, California 91109 Received 31 March 1976; revised'9 November 1977 ABSTRACT Absolute spectral energy distributions for 65 metal-poor stars, spanning a wide range in temperature, luminosity, and metal content, are given. Five local globular clusters and five M31 globulars are also described. The wavelength index sequence of O’Connell (1970, 1973) has been used. Continuum and feature indices are compared internally and with those of the Population I stellar sequence of O’Connell. His discussion of the usefulness of these indices as temperature, luminosity, and metallicity criteria is extended to metal-poor objects. Empiri- cal relationships between [Fe/H], color, and certain feature indices have been calibrated and applied to 19 objects with previously undetermined [Fe/H] values. I. introduction faint stars was also influenced by their compatibility with our observing schedule. The spectrophotometry of Population II objects de- Observed objects include virtually all northern stars scribed herein was performed to provide a data base for brighter than mv = 8.5 of indicated metal deficiency population syntheses of metal-poor stellar systems. The [Fe/H] <—1.0 and about two-thirds of those of mod- present paper deals only with the energy distributions erate metal deficiency, —0.5 > [Fe/H] > —1:0, cited in of these objects and the relationships between energy literature available through 1971. At magnitudes fainter distributions and metallicity, topics of interest in them- than = 8.5 the incompleteness of our sample becomes selves. substantial. Our work closely parallels that of O’Connell (1973, Table I gives pertinent information for observed stars. hereafter 073). It extends the Population I results of Photometric data are averaged values from Blanco et al 073 and Spinrad and Taylor (1971) to a wide range of (1968). Most radial velocities are from the catalogs of metal-poor objects. Wilson (1953) or Eggen (1962, 1964). References for other information, including identification as a metal- II. observational program and data poor star, are given in the table. Because additional data reduction on some stars have become available since the observa- tions were performed, the values given for [Fe/H] in a) Selection of Stars Table I, the best current values, are greater than —0.5 in a few cases. It was our objective to observe a large number of stars widely representative of Population II spectral types, luminosity classes, and degrees of metal poorness. Sev- b) Selection of Globular Clusters eral practical considerations imposed limitations on that goal. Our stellar sample was constrained by the following Although they provide a valuable supplement to the requirements. stellar data, the clusters were chosen as candidates for To facilitate individual scan times of less than 4 h with population synthesis. Five local clusters were picked to photon count errors less than 2% (3% in the ultraviolet) test and refine our synthesis technique while five M31 only early subdwarfs and horizontal branch stars with globulars were selected as objects for investigation. [The mv < 10.0 and late subdwarfs and giants with mv < 9.0 synthesis results are described elsewhere (Christensen were considered. Stars with <5 < —20° were rejected. 1972).] Observed clusters are described in Table II. Binaries were excluded unless the components could be The strongest constraint in the selection of all clusters completely separated (as was the case with the widely was sufficient apparent luminosity. The only accessible, spaced pair HD 134439 and HD 134440). HD 165195 but unobserved, local cluster sufficiently bright for our and HDE 232078 were the only observed stars with instrumentation was M71. It was rejected because of known E(B — V) greater than 0.10. Stars with known heavy light contamination resulting from its low galactic or inferred metal deficiencies less severe than [Fe/H] latitude. = “0.5 were excluded. Stars with published composition The five M31 globulars represent the full range of van analyses were favored over those without. Choice of some den Bergh’s (1969) line strength index L spanned by 244 Astron. J. 83 (3), Mar. 1978 0004-6256/78/8303-0244$00.90 © 1978 Am. Astron. Soc. 244 © American Astronomical Society • Provided by the NASA Astrophysics Data System 4C 4 2 . 83. 245 C. G. CHRISTENSEN: ABSOLUTE SPECTRAL ENERGY DISTRIBUTIONS 245 Table I. Program stars. U-B <5(U-B [Fe/H] Rad. Vel. References 6(U-B) [Fe/H] Rad. Vel. 1978AJ [km/sec] [km/sec] HD 2665 7,65 1.00# -1.56 -383 1 HD 126778 8.18 .67 19 HD 3546 4.37 .87 -0.75 -84 2,3 HD 128167 4.46 -.08 -0.54 6.7.8.37 HD 6755 7.68 .72 -1 .04 -320 HD 130952 4.94 .74 -0.22 2.3.37 HD 6833 6.74 1.18 -0.85 -245 HD 134439 9.12 .78 .19 .20 292 13 HD 9774 5.28 .96 -4 5 HD 134440 9.44 .86 .31 .16 306 13 HD 10700 3.50 .73 .21 .09 -0.31 -16 6.7.8.34.37 HD 135722 3.50 .95 .68 .04 -12 2.3.37 HD 19445 8.00 .47 -.24 .25 -1.71 -139 9.10.11.37 HD 140283 7.26 .48 -.20 .22 -171 8.9.10.11.12.15.20.37 HD 25329 8.51 .87 .36 .28 -1 .81 -30 8.12.13.14.37 HD 142574 5.44 1.59 1 .94 -61 26 HD 37160 4.08 .95 .64 -0.40 99 2.3.36.37 HD 144579 6.67 .73 .21 -60 8 HD 43039 4.33 1 .02 .80 -0.21 20 3.37 HD 148349 5.24 1.72 2.03 100 26 HD 44007 8.06 .85 .22 167 15 HD 151937 6.58 1.25 1.17 -43 30 HD 46703 8.92 .50 .25 -75 16,17 -15° 4515 9.2 .62* 18 HD 60552 6.70 .49* 18 HD 157089 6.95 .66 -.02 .14 -0.56 -162 8.10.12.37 HD 60778 9.10 .10 .14 39 19 HD 161817 6.96 .18 .14 .00 -1.6 -363 9,12,15,19,20 HD 64090 8.34 .60 -.12 -230 8,13,15 24.25.27.31.37 HD 73394 7.70 1.03* -96 17 HD 165195 7.35 1.18 .68 -2.70 0 3.12.23 HD 74462 8.74 .97 .53 -168 15 HD 165908 5.10 .52 -.10 -0.46 1 10.12.37 HD 74721 8.72 .03 .13 9 13.19 HD 175305 7.17 .78 .16 -188 19.30 HD 79452 5.97 .86 .37 2,3 HD 182762 5.15 .99 .81 1 5 HD 81192 6.44* .94* 5 HDE 232078 8.48 1.95 2.15 -1.30 -387 12,32,33 HD 84937 8.29 .41 8,15,20,21 HD 185657 6.5 .99* -0.51 -85 12.34 HD 85504 6.01 -.04 97 22 HD 186776 6.4 1.60* -97 26 HD 86986 7.99 .14 .16 13 15.24.25.37 HD 188510 8.83 .59 -.12 .24 -201 17.30 HD 88609 8.61 .91* -31 17 HD 193901 8.64 .55 -.13 .21 -175 8.30 HD 90362 5.58 1 .52 1 .86 32 26 HD 196610 6.3 1 .46* -66 26 HD 94028 8.21 .48 -.18 .20 62 8,13,20 HD 201626 8.14 1.11 -152 12.35 HD 103095 6.45 .75 .17 .19 -98 7.8.12.15.37 HD 205539 6.30 .36* -42 17 HD 106223 7.44 .30 -.08 -17 25,27,28 +17° 4708 9.46 .44 -296 25 HD 107328 4.95 1.16 1.15 -0.41 35 2.3.37 HD 215373 5.08 .97 13 5 HD 109995 7.61 .04 .06 -1 .9 -132 12.19.24.25.29.37 HD 219615 3.69 .92 .57 -0.17 -14 36.37 HD 117880 9.08 .04 .06 -45 15.19 HD 219617 8.17 .47 -.20 -1.40 15 8,9,10,12,15 HD 122563 6.20 .91 .38 -22 3.12.15.20.23.37 HD 221170 7.69 1.07 .62 -2.70 -120 3.12.15.23 HD 123598 7.0 1.62 58 19 HD 222107 3.88 1.02 .68 -0.78 7 2,3 References for Table I (1) Koelbloed (1967). (20) Sandage(1964). (2) Heifer and Wallerstein (1968). (21) Greenstein (1965). (3) Wallerstein and Helfer (1966). (22) Eggen (1966). (4) Cayrel de Strobel (1966). (23) Wallerstein ei ö/. (1963). (5) Oke (1969b). (24) Kodaira, Greenstein, and Oke (1969). (6) Strom, Cohen, and Strom (1967). (25) Oke, Greenstein, and Gunn (1966). (7) Sandage and Eggen (1959). (26) Deutsch, Wilson, and Keenan (1969). (8) Strom and Strom (1967). (27) Burbidge and Burbidge (1956). (9) Aller and Greenstein (1960). (28) Slettebak, Bahner, and Stock (1961). (10) Wallerstein (1962). (29) Wallerstein and Hunziker (1964). (11) Melbourne ( 1960). (30) Eggen (1964). (12) Cayrel and Cayrel de Strobel (1966). (31) Kodiara (1964). (13) Cayrel (1968). (32) Preston and Bidelman (1956). (14) Pagel and Powell (1966). (33) Helfer, Wallerstein, and Greenstein (1959) (15) Eggen and Sandage(1959). (34) Pagel (1964). (16) Bidelman (1965). (35) Wallerstein and Greenstein (1964). (17) Bond (1970). (36) Greenstein and Keenan (1958). (18) MacConnell (1970). (37) Morel et al. (1976) and references therein. (19) Eggen (1969).