.429A .135. THE VISUAL MULTIPLE SYSTEM CONTAINING BETA LYRAE* . Helmut A. Abt Kitt Peak National Observatory f 62ApJ. 19 Hamilton M. Jeeeers, James Gibson Lick Observatory, University of California AND Allan R. Sandage Mount Wilson and Palomar Observatories Carnegie Institution of Washington, California Institute of Technology Received September 20, 1961 ABSTRACT Beta Lyrae is a member of the visual multiple system ADS 11745 and has five companions which range in magnitude from 7.2 to 15 2. Previous and new astrometric measures of the three brightest com- panions (B, E, and F) yield motions that are probably consistent with physical association with ß Lyrae. Spectroscopic measures of these three companions show that one of them (E) is probably not a member. Another companion (B) is a spectroscopic binary, for which orbital elements are derived. Photoelectric measures show that the two faintest companions (C and D) are not physically associated with ß Lyrae From the association of companions B and F with ß Lyrae we derive a reddening, EB-v, of 0 065 mag., a distance modulus of 7.1 mag., and a luminosity, Mv, for ß Lyrae of —3 9. This leads to a secondary mass for ß Lyrae that is greater than that of the primary. I. INTRODUCTION Beta Lyrae is an eclipsing binary which has been extensively observed (e.g., Struve 1958) and has been unusually productive of information on gaseous streams in a close binary system. The system consists of, in addition to the gaseous streams, a B8 star of high luminosity and a spectroscopically invisible secondary, often assumed to be of spectral type F. Definitive values for the radii and masses have not been determined from the light- and radial-velocity curves because of the contamination of the former by the luminous streams. Kuiper (1941) and others have tabulated values of the radii and masses for various assumed values of the mass ratio, and, on the expectation that the primary is the more massive star, Kuiper suggested a luminosity for the primary oí Mv = —7.6. However, he realized that this luminosity might be too high for three reasons: (1) Struve’s estimate of the luminosity of the primary from the appearance of its spectrum gives Mv considerably fainter than —7.6; (2) if the principal visual companion (ADS 11745 B) to ß Lyrae is physically associated with the latter, the luminosity of ß Lyrae is Mv ^ —4.5; (3) the systemic radial velocity of the ß Lyrae system gives no evidence of galactic rotation, although such evidence would be expected if the binary were as distant as corresponds to a luminosity of Mv = —7.6. More recently Struve (1958) has reiterated the first objection to the higher luminosity. Boyarchuk (1959) estimated the luminosity of the visual companion from the equivalent widths of the HY-He lines and derived Mv — —2.7 for the primary of ß Lyrae. Beta Lyrae is a member of a well-known visual multiple system (ADS 11745 = ß 8868) which has components listed in Table 1. If some or all of the five companions to * Contribution from the Kitt Peak National Observatory, No. 13. The spectroscopic observations were made while one of the authors (H. A A) was a guest investigator at the Mount Wilson Observatory. f Operated by the Association of Universities for Research in Astronomy, Inc , under contract with the National Science Foundation. 429 © American Astronomical Society • Provided by the NASA Astrophysics Data System .429A 430 H. A. ABT, H. M. JEFFERS, J. GIBSON, AND A. R. SANDAGE .135. ß Lyrae are physically associated with it, the color-magnitude diagram for these com- panions will yield a good distance modulus. It is the purpose of this paper to present new 62ApJ. astrometric, spectroscopic, and photometric measures of the companions to ascertain 19 whether this hope can be fulfilled. II. ASTROMETRIC MEASURES Early measures in the system ADS 11745 are collected by Burnham (1906) and Aitken (1932). Recent measures are listed in Table 2. Also listed there are photographic meas- ures on plates taken with the automatic double-star camera on the Lick Observatory 36-inch refractor. The internal mean error of the final results, which depend on numerous settings, are O''006, 0''008, and 0''017 for plates numbered 2337, 2338, and 2356, respec- tively. These errors are rather large because of the large inequality in magnitudes. In Figure 1 all known measures or means are plotted with weights proportional to the number of measures averaged, except that recent photographic measures have been weighted 5. Least-squares lines have been determined. The motions in position angle are due primarily to the effect of precession, which amounts to — 0°6525 per century (Chau- vent 1891). After allowing for this, we find the actual changes in position angle (AP.A./ At) and separation (Ap/At) that are listed in Table 3. The astrometric data on stars C TABLE 1 Components of ADS 11745 Position Separa- Component Name ADS Angle tion mag with A from A A ß Lyrae 3 0 B ß2 Lyrae 6 7 149c 46" C 13 0 247 46 D 14 3 68 64 E BD-f-33°3222 9 2 318 67 F BD+33°3225 9 0 19 86 TABLE 2 Recent Astrometric Measures in ADS 11745 P.A. No. Observer Pair Date (Epoch) Sep Measures 1928 05 148°8 45''82 3 Komendantoff (1935) 1929 59 148 5 45 59 3 Aller (1930) 1949 71 148 70 45 76 Kranjc (1951) AB 1955 69 148 51 45 733 2 Bottger (1958) 1959 852 148 697 45 718 61 Present (No 2337) 1959 869 148 747 45 700 34 Present (No. 2356) 1929 59 318 1 66 97 3 Aller (1930) AE 1959 852 317 473 66 997 54 Present (No. 2338) 1959 869 317 506 66 965 34 Present (No 2356) 1929 58 18 3 84 99 2 Aller (1930) AF 1959 852 18 562 86 035 54 Present (No 2338) 1959 869 18 646 86 042 34 Present (No. 2356) © American Astronomical Society • Provided by the NASA Astrophysics Data System .429A MULTIPLE SYSTEM 431 .135. and D are insufficient to determine motions, although those of star C are probably roughly the same as those in Table 3. 62ApJ. The proper motion of ß Lyrae is given (Jenkins 1952) as 0''7 per century. In Figure 2 19 we have plotted to scale the multiple system with an arrow on A (ß Lyrae) indicating its proper motion and arrows on the other stars indicating their motions relative to A, after allowing for the precession effect. For star B we see that its well-determined motion rela- tive to A is very small compared with the latter’s proper motion, and hence it shares in that proper motion. This comparison for stars E and F is less certain. Their motions in position angle relative to A are also very small, but the motions in separation seem to be © American Astronomical Society • Provided by the NASA Astrophysics Data System .429A 432 H. A. ABT, H. M. JEFFERS, J. GIBSON, AND A. R. SANDAGE .135. appreciable compared with the proper motion of A. However, Figure 1 shows that the changes in separation are very poorly determined, undoubtedly because of the difficulty 62ApJ. in measuring pairs of stars that differ so much (7 mag.) in brightness. The elimination of 19 the 1879 mean separation for AE and the 1929 mean for AF would greatly alter the de- rived changes in separation of the components. We can ask whether the motions in Table 3 are reasonable for a multiple system. If we assume (1) the final distance modulus of 7.1 mag., (2) reasonable masses for compo- nents A (31.2 SDîo) and B (4 SJîo), and (3) a circular orbit seen pole-on, then the expected TABLE 3 Mean Motions in ADS 11745 AP A /M Ap/At AP A /At Ap/At Star Pair (Deg/Century) ("/Century) Star Pair (Deg/Century) ("/Century) AB -0 108 -0 056 AF +0 285 +0 314 AE +0 166 +0 383 Fig. 2.—The positions and motions of the components of ADS 11745 The scale at the lower right is for both dimensions (in seconds of arc) and motions (in seconds of arc per century). The arrow on com- ponent A (ß Lyrae) indicates the extrapolated proper motion of that star in a century, while the arrows on components B, E, and F show the motions of those stars relative to A in the same time interval and after removal of the precession effect This shows that if the proper motion of A is well determined, star B, at least, shares it. motion in position angle for AB is 0?162 per century. The observed amount is 0?108 per century. On the other hand, if, instead of the third assumption, we assume a circular orbit seen equator-on and with component B at, say, 45° to the line of sight, then the expected motion in separation is 0''077 per century compared with an observed amount of 0'i056 per century. Therefore, the motion of B relative to A is reasonable for a double- star system. The motions of E and F are far more difficult to predict because the assumption of a two-body system is probably not valid for these less massive, more distant stars. How- ever, their general similarity with that of B, after allowance for the poorer determina- © American Astronomical Society • Provided by the NASA Astrophysics Data System .429A MULTIPLE SYSTEM 433 .135. tions, indicates that their motions may also be attributable to motion in the multiple system.