Ρ Puppis : a New Short-Period Variable Star

ρ PUPPIS : A NEW SHORT-PERIOD VARIABLE STAR

Olin J. Eggen Lick Observatory, University of California

Photoelectric observations by the writer in 1951-52 with the 9-inch Oddie refractor of the Commonwealth Observatory, Mount Stromlo, Australia, indicated that the light of /aPuppis varied approximately 0.15 mag. The light variation was also independ- ently discovered at the Cape Observatory.1 On four nights in March 1956, the light of this star was compared with that of ÇPuppis, with the 12-inch Lick refractor, with the results as shown in Figure 1. Data on these two stars follow : Spectral Star a (1900) δ VE Type P Puppis (Max.) 8h 3^3 -24o01' 2^68 +0^30 F6II ξ Puppis 7 45.1 —24 37 3.31 +1.18 G31b

Am I I I I I I I I I I I + cTes o# o" X · o x x · φ + 4- Ο+λ +Χ υ -· © + . ^ ^ 'i + 0.60 i β * -Η · χ • χ March 19,1956 Ç · · + · March 20,1956 *0 · + + 0.55 Ο March 22,1956 ^ + March 26,1956 χ Ό Ο ^ Φ • ·χ· +

Phase 0¾ 0.0 0.2 0.4 0.6 0.8

Fig. 1.—Light curve of ρ Puppis from photoelectric observations on four nights.

Alternate deflections were taken on the variable and on the comparison star using a 1P21 photomultiplier and a yellow filter (Corning 3385). All deflections were reduced to no atmosphere with the absorption coefficient obtained from the observations of the comparison star (0^15 at the zenith). The magnitude differ-

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enees, obtained from each deflection of the variable as compared with the mean of those of the comparison star, are given in Table I — — WpPuppis). The dates given are helio-

TABLE I Photoelectric Observations of p Puppis March 19, 1956 Phase Am March 22, 1956 Phase Am JD 2435552.825 0^114+0^632 JD 2435555.809 0^277 +0^572 .837 0.199 0.598 .817 0.334 0.558 .847 0 . 270 0 . 572 . 826 0 . 398 0 . 548 .854 0 . 319 0 . 560 . 838 0 . 482 0 . 538 .865 0.397 0.535 . 848 0 . 553 0.538 .875 0.468 0.538 . 858 0.624 0.538 .885 0.539 0.522 . 868 0.696 0.550 .898 0.631 0.535 . 879 0.773 0.590 .911 0.724 0.578 . 886 0 . 823 0.620 .918 0.773 0.592 . 895 0.887 0.625 .929 0.851 +0.638 . 906 0.965 0.645 .912 0.007 0.635 .919 0 . 057 0 . 628 .924 0.092 0.618 .929 0.128 0 . 615 .933 0.158 +0.598

March 20, 1956 March 26, 1956 53.811 0.107 +0.625 59.811 0.660 +0.528 .819 0.163 0 . 600 .820 0.738 0.558 .827 0.220 0.585 .827 0.773 0.592 .834 0.270 0.578 .835 0 . 830 0.617 .841 0.319 0 . 568 .843 0.887 0.626 .849 0 . 376 0 . 558 .851 0 . 943 0 . 628 .855 0.419 0.530 .859 0.000 0.624 .862 0.468 0.550 .867 0.057 0.622 .869 0.518 0.525 .872 0.093 0.624 .876 0.568 0.525 .878 0.135 0.613 .881 0.603 0.535 .885 0.185 0.596 .891 0.674 0.538 .891 0.227 0.576 .896 0.709 0.552 .897 0.270 0.566 .901 0.745 0.570 .903 0.312 0.553 .909 0 . 802 0 . 595 .907 0.341 0.550 .915 0.844 0.612 .926 0 . 922 0 . 638 .936 0.993 0 . 645

centric and the phases were computed from the following ele- ments : Max. = JD(Hel. )2435555.911 + 04141-E.

The most obvious class of variable stars to which ρ Puppis could be assigned is the small group typified by ôScuti. Four pos- sible members of this group, all of which have been studied at the Lick Observatory, are the following :

y ε (P-V)e Spectral Star (max.) (mean) Period Type DQ Cephei2 7Ψ24 +0^20 04079 F4 III* CC Andromedae3 8.45 +0.22 0.125 F2 IVt ρ Puppis 2.68 +0.31 0.141 F6IIÍ δ Scuti4 4.60 +0.23 0.194 F3 III-IV5

Radial Velocity Range Form of Star Am (km/sec) Μτ Light Curve DQ Cephei2 0^06 Var.? 20: Var.? CC Andromedae3 0. 24 Var. Var. ρ Puppis 0.12 Const. ? 11 +0.2 Const. ? 4 δ Scuti 0.29 Var. 6-15 +1.1 Var.

* This spectral type is due to W. P. Bidelman, who considers this star to be both later and more luminous than β Cassiopeiae, now classified F2IV. At the time of Walker's classification of DQ Cephei as F2 II, Pub. AS.P., 64, 192, 1952, β Cassiopeiae was classified F2 III. t G. H. Herbig has stated (private^communication) that the spectrum of this star is rather similar to that of β Cassiopeiae. $ This spectral type is given in the Yerkes Atlas of Stellar Spectra; W. P. Bidelman has pointed out, however, in Ap. /., 113, 304, 1951, that "the Can lines are rather weak for the type given."

The periods and the shapes of the light curves of the other three stars of this group are probably variable but the limited observa- tional material presented here indicates no such variation for Ρ Puppis. Although the southern declination of ρ Puppis makes observations difficult from Mount Hamilton, it can be definitely stated that the light curve of this star is certainly more stable from cycle to cycle than those obtained by Fath for δ Scuti or by Lind- blad and Eggen for CC Andromedae. The listed spectral types are rather inhomogeneous. The radial velocity range is unknown

for CC Andromedae, uncertain for DQCephei,2 11 km/sec for pPuppis from 22 Cape6 and 12 Lick7 spectrograms, and varies between 6 and 15 km/sec for ÔScuti.8 Extensive spectroscopic and photometric investigations of δ Scuti have been published by Paddock and Struve8 and Fath,4 respectively, and a simultaneous photometric and spectroscopic study of CC Andromedae has been completed by O. C. Wilson and M. F. Walker.9 The results for ÔScuti and CC Andromedae show that the light and velocity curves are approximate mirror images of each other. A detailed description of the spectrum of ρ Puppis has been given by Green- stein.10 The visual absolute magnitudes of δ Scuti and p Puppis tabu- lated above are determined from trigonometric parallaxes of 0^020 and 0^031, respectively; the individually determined absolute values are 0^020, Allegheny, (//019, McCormick, and (//020, Yale, for δ Scuti, and 0^027, McCormick, O'/OIQ, Yale, and 0^049, Cape, for /3 Puppis. Both mean parallaxes could be materially strengthened by a redetermination. The location of these stars in the color-luminosity array will be discussed in more detail else- where but it can be said that they occur in a portion of the array for the stars near the sun that is similar to the "variable star gap" in the arrays for the globular clusters.

1 Cape Mimeogram No. 1, 1953. 2 M. F. Walker, Pub. AS.P., 64, 192, 1952 and 65, 39, 1953. 3 P. O. Lindblad and O. J. Eggen, Pub. AS.P., 65, 291, 1953. 4E. A. Fath, Lick Obs. Bull, 17, 175, 1935 (No. 479) and 18, 77, 1937 (No. 487). 5 A. Slettebak, Ap. /., 121, 653,1955. 6 H. Spencer Jones, Cape Ann., 10, part 8, 1928. 7 W. W. Campbell and J. H. Moore, Pub. Lick Obs., 16, 1928. 8 G. F. Paddock and O. Struve, Ap. /., 119, 346,1954. 9 Carnegie Inst. Washington Yearbook, 53, 9, 1954. 10 J. L. Greenstein, Ap. /., 107, 151, 1948.