Pub. Astron. Soc. Pacific, Volume 83, December 1971 LUMINOSITIES AND MOTIONS OF THE F-TYPE STARS. 1. LUMINOSITY AND METAL ABUNDANCE INDICES FOR DISK POPULATION STARS O. J. EGGEN Mount Stromlo and Siding Spring Observatories, Research School of Physical Sciences The Australian National University Received 25 June 1971 Intermediate (uvbyß) and broad (UBV) band colors are now available for over 1000 bright (HR), F-type stars for which accurate apparent motions have also been determined. The present paper examines the luminosity ( a[ci] ) and metal abundance (8(17— B), and Δ [mi] ) parameters for Hyades group stars (§ II), other young disk stars including the Sirius group (§ IV), and old disk stars, including the Wolf 630 and ζ Herculis group members (§ V). A procedure is developed for computing luminosities from the intermediate-band indices for both young and old disk population objects. The comparison between photometric parallaxes and the group or trigonometric values indicate errors of not more than about 0Φ3 for the photometric luminosities. Ultrashort-period cepheids in the young disk population and a comparison between the metal abundance parameters Δ [mi] and 8 (U— B) are also briefly discussed. Key words: disk population stars — photometry — F-type stars I. Introduction are on the Cape refractor system. Most of the If we define F-type stars as those with (B—V) southern stars have therefore been reobserved on between +0Γρ28(Ρ0) and +0^0(00), there are the UBV system with the 40-inch reflector at approximately 1200 such objects brighter than Siding Spring. Also, UBV results, mainly from visual magnitude 6^5 in the Catalogue of Bright observations with the 20-inch reflector at Palo- Stars (HR). Fifteen percent of these, mostly mar, are available for about 70 percent of the southern stars, have no radial velocity available northern stars. Both the northern (Eggen 1968) and the proper motions for 1 or 2 percent are and southern (e.g., Eggen 1970α) observations poorly determined. Intermediate-band (uvbyß) have been carefully tied to the UBV system. and broad-band (UBV) photometry is available The use of UBV photometry for the deter- for most of the remaining stars. The majority of mination of the chemical composition of main- the intermediate-band results are contained in sequence stars has been described elsewhere catalogs by Strömgren, Ferry, and Crawford (e.g. Eggen 1964 and references therein). The (preprint) and Crawford et al. (1966) for northern main difficulty, for the F-type stars, is in the stars and by Eggen and Stokes (in preparation) separation of abundance and gravity effects on for southern objects. Results for some bright the (17—B) colors. This difficulty is overcome southern stars have also been published by with the use of uvbyß photometry (e.g., Ström- Crawford, Barnes, and Golson (1970) and addi- gren 1963,1966; Crawford and Strömgren 1965). tional uvby observations of northern stars have The purpose of this paper is to reexamine the been obtained by Perry (1969) and Eggen (un- calibration of the photometric luminosity and published). The stars brighter than visual magni- abundance parameters of the disk population tude 5 have been observed on the UBV system with the large amount of data now available. by Johnson et al. (1966) and by Cousins (1967). The following standard nomenclature has been A few results by H. L. Johnson and his collabo- adopted. rators for fainter, northern stars are available in uii — (v—b) — (b — j/); metal line index the literature. Most of the southern stars have Ci = (u — v) — (v — b); Balmer been observed at the Cape Observatory, but un- discontinuity index fortunately, except for those in the equatorial [ci] = Ci — 0.2ß(b—y) = reddening free zone (δ = —10° to +10° ), the ultraviolet colors index 741 © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 742 O. J. EGGEN [mi] = Wh + 0.1S{b—y) = reddening free for Hyades main-sequence stars (e.g., Eggen and index Sandage 1959; Eggen 1965α) which is assumed to [u—b] = [ci] + £[771^ ; reddening free be also the relation for age-zero main-sequence index stars. The (β, ), (/3, [ci]) and (ß, ib-y)) Δ [rrii] = [mi] (Hyades main sequence)— relations for Hyades main-sequence stars in [mi] (star at a given/3 or (b — j/) Table I are derived by Crawford and Perry A[ci] = [ci] (star) — [ci] (zero-age main (1966); this (β , (b—y)) relation is also assumed to sequence) at a given β or {b —y) hold for age-zero maiiî-sequence stars. The The values of mi and Ci and all parameters based (β, [cj ) relation for age-zero main-sequence upon them will be given hereinafter in terms stars is derived from a more condensed version of 0^001. given by Strömgren (1963) and the (β. My) rela- tion is based on the (B—V, My) relation derived II. Hyades Stars by Eggen (1965α) from the Hyades and Pleiades Table I contains the (U—B), (B—V) relation clusters. TABLE I Photometric Parameters for Hyades and Age-Zero Main-Sequence Stars Hyades Age-Zero Main Sequence ß [mi] [ci] [d] b-y B-V. My U-B F 2?81 229 846 804 131 +0^21 +2?55 +0?13 7.5 2.80 229 817 782 142 +0.225 +2.6 +0.12 7.5 2.79 227 790 760 152 +0.245 +2.7 +0.11 7.5 2.78 225 763 742 161 +0.255 +2.75 +0.105 7.5 2.77 223 738 704 170 +0.27 +2.8 +0.095 8.0 2.76 220 714 666 179 +0.28 +2.85 +0.085 8.0 2.75 219 690 650 188 +0.295 +2.9 +0.07 8.0 2.74 217 665 625 198 +0.31 +2.95 +0.06 8.5 2.73 216 630 598 208 +0.325 +3.0 +0.05 8.5 2.72 215 596 569 218 +0.34 +3.05 +0.03 9.6 2.71 215 562 540 229 +0.35 +3.1 +0.025 9.0 2.70 215 527 510 240 +0.365 +3.2 +0.02 9.5 2.69 216 485 480 252 +0.38 +3.3 +0.015 9.5 2.68 218 442 442 264 +0.405 +3.45 +0.01 10 2.67 220 406 406 279 +0.43 +3.65 +0.005 10.5 2.66 224 381 381 294 - +0.46 +3.85 0.00 11 2.65 230 356 356 309 +0.485 +4.0 +0.02 12 2.64 236 330 330 324 +0.51 +4.15 +0.04 13 2.63 245 307 307 340 +0.535 +4.35 +0.065 14.5 2.62 257 284 284 356 +0.56 +4.5 +0.09 16 2.61 271 265 265 373 +0.59 +4.7 +0.12 17.5 2.60 286 247 247 390 +0.62 +4.9 +0.155 19 (2.59) 302 231 231 407 +0.65 +5.1 +0.19 (21) Table II contains the members of the Hyades is inapplicable. In addition to the photometric group, other than Hyades cluster members, parameters. Table II contains the following infor- amongst the stars in the Catalogue of Bright mation: Stars. An additional ten probable group mem- N,N: The source of the UBV and uvbyß bers have been omitted because they are so near results, respectively. The letters "C" and "J" the apex (or antapex) of the group motion that refer to UBV observations, already mentioned, proper motion contributed negligibly to the V- by Cousins or by Johnson and their collaborators. velocity and therefore the concept of a group Observations with the 20-inch Palomar reflector parallax, derived from forcing V = —16.8 km/sec. or 40-inch Siding Spring reflector are indicated © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System F-TYPE STARS 743 TABLE II Hyades Group Members HP V£ B-V U-B N,N U W m— M HR b-y [mi] [ci] dU dV dW μδ Sp. AR (km/sec) (O'.'OOl) 4757 5^56 +0?36 +0^055 2 / S + 33 -16.8 - 5 + 84 + 5.9 4^87 230/1* 240 211 671 2.700 + 3 - 2 0 - 4 gFO 2.9 6680 6.25 +0.40 0.00 2 / S + 41 -16. 8 -10 + 200 + 15.0 3.27 327 268 208 468 2.677 + 7 - 6 - 1 - 30 F5 IV 1.0 7570 4.96 +0.57 +0.09 C,2 + 33 -16.8 -11 +665 + 11.5 0.28 370 380 245 343 2.625 + 30 -12 0 + 186 F8 V 0.26 8673 6.34 +0.48 -0.01 3,S + 36 -16. 8 -15 +225 + 16.9 2.69 410 314 220 386 2.651 + 8 - 8 - 2 - 84 dF5 0.8 8774 6.27 +0.45 0.00 2, S + 42 -16. 8 - 3 + 155 + 14.5 3.82 415 296 231 402 2.656 + 6 - 5 + 1 - 9 F5 1.4 13871 5.80 +0.44 0.00 2 , S + 39 -16.8 -12 + 173 +26.0 3.10 656 288 223 440 2.655 + 5 - 7 0 - 59 dF3 0.65 15634 6.49 +0.29 +0.04 2,2 + 40 -16. 8 - 9 + 84 +25.0 4.65 733 184 217 773 2.765 + 4 - 1 + 2 + 36 dA9 1.3 17094 4.27 +0.31 +0.075 CJ,S + 38 -16.8 - 9 +284 +28.8 1.77 813 189 221 724 2.743 + 8 -10 + 5 - 29 F0 IV 0.21 18404 5.80 +0.40 0.00 4,S + 41 -16.