501. New observations by Stickland & Weatherby do not fit the period derived by H.A. Abt & M.S. Snowden (ApJ, 25, 137, 1973). There is still some doubt about the period, one near 475 also being possible, but the value given in the Catalogue is preferred. The star was considered as an Si, Cr object by Abt & Snowden, Stickland & Weatherby suspect that it is an Hg, Mn star.

502. The secondary spectrum was thought to be visible on one spectrogram. If it is, the mass-ratio would appear to be 0.81. In IDS an 8.1 companion is listed at 6".1.

503. The magnitude is an estimate. Griffin calls attention to the mass-function, large for a system showing only one spectrum, and suggests that the secondary component itself is a short-period binary, perhaps containing two main-sequence stars of type about F4.

504. The recomputation by Lucy & Sweeney based on observations by O. Struve (ApJ, 104, 253, 1946) has been preferred to Struve's original solution (e = 0.1) because a photoelectric (BV) light-curve (K.T. Johansen et al., A&A, 11, 20, 1971) shows e cos = 0. The epoch is T, and the orbit was assumed circular after a preliminary solution gave e = 0.0. The two stars are nearly equal in size, but the primary gives 0.91 of the total light in V. The orbital inclination is about 89.7. A new analysis of these observations by M. Mezzetti et al. gives very similar results. The depth of eclipse in V is just over 2.5, but unfortunately the maximum and minimum V magnitudes cannot be deduced from the data given by Johansen et al.. In view of the excellent light-curve now available, the system would be worth re-observing spectroscopically.

505. The magnitudes given are approximate and the star spends most of the time at the fainter magnitude. No epoch is given; the orbit is assumed circular. The values of K and V are derived from measures of the core of the H emission line.

506. According to IDS there is a 9.5 companion at 51".1.

507. A few old Mount Wilson measures give velocities above the mean curve derived from recent CORAVEL observations. The authors believe this cannot be accounted for by systematic errors between observatories and suggest that V varies.

508. The new observations add little to those of G.H. Herbig (ApJ, 132, 76, 1960) but show that the elements deduced depend on the lines measured and may vary with time. The elements given in the Catalogue are based on measures of the peak of the He II emission. The orbit is assumed circular and the epoch is a photometric one (approximately maximum brightness) taken from the work of M.F. Walker (Mitt. Sternw. Budapest, 57, 1, 1965). The magnitudes given are an approximate indication of the range of the highly variable light-curve. Photometry of the system has been discussed by D.A. Allen & A.M. Cherepashchuk (MNRAS, 201, 521, 1982) and P. Szkody, J.A. Bailey & J.H. Hough (ibid., 203, 749, 1983). The former investigators find that when the star is quiescent, the variation is caused primarily by the ellipticity of the M-type dwarf and they estimate that the orbital inclination is between 50 and 70. A detailed model is discussed by J. Liebert et al. (ApJ, 225, 201, 1978) and spectrophotometric observations are reported and interpreted by D.T. Wickramasinghe & N. Visvanathan (MNRAS, 191, 589, 1980).

509. This star (from the Cape Photographic Durchmusterung) was recognized as a cataclysmic variable by R.F. Garrison et al. (ApJ, 276, L13, 1984). The magnitude given is the mean of their published results; the star flickers over a range of 0.1 and shows variations of about 0.5 over several years. Garrison et al. used this system, at present the brightest known cataclysmic variable, to estimate the space density of such stars. Two studies have been published by the authors cited in the Catalogue; the other is in MNRAS, 204, 35P, 1983). A circular orbit is assumed and the epoch is the time of inferior conjunction of the emission-line source. The results are described as preliminary by the authors themselves. They estimate the orbital inclination at 63. A brief account of the UV spectrum was published by H. Böhnhardt et al., IAU Colloq. No. 3749, 1982.

510. This is another cataclysmic variable in which caution is needed in the interpretation of the `orbital elements'. The value of K = 193 km/sec is derived from late-type absorption lines in the spectrum. That of K is derived from emission lines which, at least partially, arise from the disk surrounding the white dwarf. A circular orbit has been assumed, the epoch given is the time of spectroscopic conjunction with the red star in front. The two velocity curves are 180 out of phase. E.L. Robinson (ApJ, 186, 347, 1973) has also obtained spectrograms of the red region. From the H emission he has derived K = 137 km/sec, V = -45 km/sec, and assumed the other elements were as derived by Kraft et al.. He found evidence that the system is losing mass. Robinson has also published high-speed photometry of the system (ApJ, 180, 121, 1973). Although B. Warner & R.E. Nather (S&T, 43, 82, 1973) earlier reported grazing eclipses of the hot spot in this system, Robinson found no evidence for them. Kraft et al. estimate the orbital inclination to be in the range 50 to 60. The B magnitudes given in the Catalogue are derived from data in their paper. A theoretical model for the system has been proposed by B.P. Flannery (ApJ, 201, 661, 1975). A spectrophotometric study of this system has been published by A.L. Kiplinger (ApJ, 236, 839, 1980).

511. This is one of the few pulsars in a binary system with a known orbit - an orbit of very different characteristics from those of the first known member of the class, PSR 1913+16. The epoch is an arbitrary reference epoch. The measured quantity, of course, is not radial velocity but pulsar period which is determined very accurately. From its variations, i>a sin i can be deduced. A compete orbital period has not yet been observed. No magnitude or spectral type are available, and V cannot be determined. A circular orbit was assumed.

512. Lucy & Sweeney adopt a circular orbit.

513. The epoch is the time of primary minimum (which is only slightly deeper than the secondary). The small eccentricity is in agreement with that found photometrically and the system displays apsidal motion in a period of approximately 3,200 years. The two stars are nearly equal and the orbital inclination is close to 88. Both spectroscopic and photometric observations are affected by a visual companion. According to IDS this is 1.1 fainter than the eclipsing pair and separated by 0".3. Andersen et al. believe the companion to be fainter and probably to be a spectroscopic binary itself.

514. 515. These systems compose ADS 6828. The orbital period of the visual pair is 53 and its major semi-axis is 0".32. Each component is a spectroscopic binary. Fekel has also detected the secondary component of the 2.5-day pair (BAAS, 10, 660, 1978) and private communication) and believes its mass-ratio to be similar to that of the 6-day pair. Although Fekel has not yet published a complete study of this interesting multiple system, he has extensive data. He has published slightly different values for the eccentricities (ApJ, 246, 879, 1981) and argues (BAAS, loc. cit.) that none of the orbits is coplanar. The eccentricity of the 6-day orbit is now found to be negligibly small and the epoch is T. Orbital elements have been published by G.A. Bakos (JRASC, 79, 119, 1985) whose results are in general agreement with Fekel's except for values of V (which may be partly affected by systematic errors) and a somewhat larger eccentricity for the 6-day pair. Bakos has also shown that the 2.5-day pair is an eclipsing binary. He derives an orbital inclination of 86 and estimates that the primary gives 0.89 of the light in V. There is a faint companion (11.5) at about 18" listed in IDS and Fekel believes it to be physically associated with the quadruple system.

516. Brighter component of ADS 6872: companion 9.8 at 1".8.

517. There is obviously a misprint in the value of T as given by Stickland et al. The correct value is presumably either 2,430,730.51 or 2,443,730.51, the latter being the more likely.

518. Popper's elements are in general agreement with those found by O. Struve (ApJ, 102, 74, 1945). The epoch is T. Slightly different values of V are found for each component. Several photometric investigations have been made (R.L. Walker, AJ, 75, 720, 1970), D.B. Wood, ibid., 76, 701, 1970), T.D. Padalia & R.K. Srivastava, Ap&SS, 35, 249, 1975) and B. Cester et al., A&AS, 32, 351, 1978). All agree that the orbital inclination is close to 89. Values obtained for the fractional luminosity depend strongly on whether the primary eclipse is taken to be an occultation or transit. Popper (Ap&SS, 45, 391, 1976) has shown that only the latter leads to a luminosity ratio in accord with the spectroscopic evidence. Cester et al., who adopt the transit hypothesis, found a fractional luminosity of 0.64 (in V) for the primary component.

519. A circular orbit was assumed and the epoch is T. The two stars are approximately equal in photographic (B) light and the spectrum is composite outside eclipse. D.M. Popper (PASP, 60, 248, 1948) classified the secondary spectrum as A3 III-V: Wesselink's classification is based on UBV measures in totality and out of eclipse. He finds that the B star is 1.12 fainter than the K star in V, but 1.4 brighter than it in U. Primary eclipse is the total eclipse of the B star by the K giant. Wesselink assumed i = 90 to derive relative radii for the two stars, but no complete photoelectric light-curve of the system has been published. Identification of the star is from the Cordoba Durchmusterung.

520. Epoch is T, based on an early time of minimum. All elements are very approximate. Sahade describes the two spectra as `of practically the same intensity'. Modern analysis of BV light-curves (D.A.H. Buckley, Ap&SS, 99, 191, 1984) confirms that, giving a fractional luminosity in V for the primary component of 0.52 and an orbital inclination close to 88.

521. This is a cataclysmic variable and a known X-ray source. The magnitude is approximate. Very few details are given of the orbital solution. In particular, no epoch is given and V had to be inferred from a plot of the velocity-curve. The value of K is derived from measures of the emission-line wings and is also approximate.

522. Investigation of this star was described as a `preliminary study' by Thackeray himself, and in view of the fairly large scatter of the observations the orbit has been classified as d. Thackeray commented on the complexity of the emission-line spectrum and compares the system with both Lyr and W Cru. There are variations in the light with the orbital period through a range of about 0.2 in V. Thackeray believed that the dominant cause of the variation is ellipticity of the components, but a partial eclipse of the region producing H emission may also be contributing. W. Strupat & C. Boehm report on some new spectra at 12Å/mm dispersion (IBVS, No. 2949, 1986).

523. Brightest component of ADS 6886: principal companion 7.2 at 10".3.

524. Not known before the Palomar--Green survey, this object is presumably a cataclysmic variable and is possibly to be identified with the X-ray source 1H0832+488. The elements given are derived from measures of the bases of the emission lines. The secondary may be a dwarf of type about K5. Epoch is inferior conjunction of the emission-line source and the orbit was assumed circular.

525. The elements obtained by Lucy & Sweeney have been preferred over those obtained from the same observations by O. Struve (ApJ, 102, 74, 1945). The epoch given is T. The only light curve available is one by J. Fetlaar (Bull. Astron. Inst. Netherl., 6, 29, 1930) from which he found i = 89.5 and a light ratio of 0.33.

526. The new results by Popper supersede his own earlier work (AJ, 62, 29, 1957); PASP, 74, 129, 1962). The orbit was assumed circular and the epoch is the time of primary minimum. The spectral type of the secondary (cooler and less massive) star is derived from its UBV colours. Popper gives a photometric solution in which he der ives an inclination of 87.5 and a light-ratio at quadratures of 0.78 in V (cooler : hotter star). P. Broglia & P. Conconi (Mem. Soc. Astron. Ital., 44, 87, 1973) obtain a very similar value for the inclination but make the fractional luminosity of the smaller star (in V) to be 0.37. B. Cester et al. (A&A, 61, 469, 1977), using the observations by Broglia & Conconi make the two stars nearly equal in luminosity, which appears contrary to the spectroscopic evidence.

527. See note for No. 469. Because most of the spectrograms of this object are only weakly exposed, Gieseking describes it as a suspected binary.

528. Sanford reports `the two components have approximately the same brightness and spectral type'. The star is a member of Praesepe and is ADS 6915 C; A is 6.9 at 45".2.

529. This W UMa system has attracted much attention, partly because its membership of Praesepe helps to clarify the evolutionary status of contact systems. The observations by Whelan et al. supersede those by D.M. Popper (ApJ, 108, 490, 1948). New observations have been published by B.J. McLean & R.W. Hilditch (MNRAS, 203, 1, 1983) in the early development of cross-correlation methods for measuring this kind of spectrum. They find K = 96 km/sec, K = 181 km/sec. It seems to us, however, that the work of Whelan et al. should still be preferred, because of their better coverage of the velocity-curve, despite the potential of the newer method. The orbit was assumed circular and the epoch is the time of primary minimum. The minimum magnitude given in the Catalogue is an estimate from the plot of the V light-curve by Whelan et al. They find an orbital inclination of 63 and that the larger component gives 0.55 of the light of the system. Similar results for the orbital inclination have been obtained by A. Yamasaki (Ap&SS, 77, 75, 1981) and R.W. Hilditch (MNRAS, 196, 305, 1981).

530. A standing reproach to spectroscopists has been removed with this publication of the first orbital elements for one of the longest-known eclipsing binaries. Fragmentary information about earlier observations had been available for some time, but inconsistencies in it were pointed out almost simultaneously by E.W. Weis (Obs., 96, 9, 1976) and A.H. Batten (IAU Symp. 73, 303, 1976). The spectral types are determined from photometric colours and spectrophotometry by P.B. Etzel & E.C. Olson (AJ, 90, 504, 1985) rather than from traditional spectral classification. The orbit was assumed circular and the epoch is the time of primary minimum. Values of V were determined separately for each component. Because the measures depend on different lines in different spectral regions, Popper & Tomkin do not consider the difference in V to be significant. A matching photometric study by Etzel & Olson has already been cited. They derive an orbital inclination close to 85 and a fractional luminosity in V for the primary star of 0.93. (Popper & Tomkin give V = 1.4). Other recent analyses (M.I. Lavrov, Trudy Kazan Obs., 39, 42, 1973) and V.A. Caracatsanis, Ap&SS, 47, 375, 1977) give similar results. Popper & Tomkin claim that the secondary has the lowest known stellar mass (0.18 M) derived directly from radial-velocity observations. There is a 10.8 companion listed in IDS at 76" separation.

531. This object was recognized as a cataclysmic variable by N.E. Kurochkin & S.Yu. Shugarov (Astron. Tsirk., No. 1114, 1980) and the period and epoch (time of minimum) are taken from their paper. It is one of few cataclysmic variables in which the spectra of both components are measurable. The magnitude given is the approximate mean out-of-eclipse magnitude according to A. Yamasaki, A. Okazaki & M. Kitamura (PASJ, 35, 423, 1983). Eclipses are about 1.5 deep in V. The variable may be associated with the X-ray source H 0850+13. The value of K for the white dwarf (upper line) is derived from emission lines of hydrogen and helium and one absorption line of helium. The measurable secondary lines include the G-band and lines of neutral metals. Schlegel et al. describe the spectrum as late G or early K, although photometric evidence might make it as late as K5. The orbit was assumed circular and the value of V is only approximately known. Schlegel et al. find a lower limit of 66 for the orbital inclination. A photometric study has also been published by A.V. Baidak & S.Yu. Shugarov (Astron. Zh., 63, 123, 1986).

532. ADS 6993, a well-known multiple system (it is at least quintuple). The magnitude refers to the combined light. This orbit is that of the visual pair AB (P = 15.04). Many other investigations of this star have been published. Those particularly concerned with the radial velocities of the components are: R.G. Aitken (PASP, 24, 16, 1912); E. Slonin (Tashkent Bull. No. 5, 159, 1934); A. Abrami (Trieste Contr., No. 321, 1963). Radial velocities which confirm Adams' orbital elements have been published by A.B. Underhill (Pub. DAO, 12, 159, 1963). She suspected a secondary variation with a period of 70. Adams also discussed the visual orbit, and found i = 39.1. The best visual orbit (adopted by W.S. Finsen & C.E. Worley, Republic Obs. Circ., 7, 203, 1970) is that by A. Abrami (Pub. Oss. Trieste, No. 321, 1963). This has some differences from Adams' orbit. High-dispersion observations have been continued at Victoria by C.D. Scarfe, and it should be possible soon to give a definitive spectroscopic orbit of this system.

533. Another member of ADS 6993 at about 3" from AB. Some spectrograms may be contaminated by light from AB.

534. See note for No. 469.

535. See note for No. 469. The observations also admit a period of 14.75.

536. See note for No. 469. These elements are based on a few rather weak spectrograms and even the period is uncertain.

537. The orbit was assumed circular and the epoch is primary minimum. Whelan et al. gave ranges for the elements K, K and V, 100 - 103 km/sec, 138 - 240km/sec, and 6 to 15 km/sec respectively; we have given the means. The orbital inclination is estimated (from the light-curve also obtained by Whelan et al.) at 68. The minima are of nearly equal depth. The system is of interest because it belongs to the very old cluster M67 and yet is very similar to TX Cnc which belongs to the young Praesepe.

538. Although this star has been known to be a two-spectra binary for some time (H.A. Abt & K.L. Moyd, ApJ, 182, 809, 1973) these elements are the first to be determined. The orbital eccentricity is insignificantly small and the epoch is T. The two spectra are described as very different in intensity. Abt & Levy classify the primary spectrum as A3, A8 and F0, from the K line, hydrogen lines and metallic lines respectively.

539. A newly discovered eclipsing variable that has attracted much interest. Two independent spectroscopic orbits have been published before Andersen's: they are by C.R. Chambliss (MNRAS, 142, 113, 1969) and D.H.P. Jones (MNASSA, 28, 5, 1969). Andersen's observations of are appreciably higher dispersion than either of the other two sets, and define beautifully all that part of the velocity curve over which the two components can be resolved. Agreement between the three sets of observations is not good, but this is probably because of the low dispersions employed in the earlier work, especially by Chambliss. The orbit was assumed circular and the epoch is primary minimum. The spectral classifications are by Jones, and were taken over by Andersen. Photoelectric observations in yellow and blue have been published by C.R. Chambliss (AJ, 72, 518, 1967) from whose paper the magnitude at minimum has been estimated. His solution has been rediscussed by H.G. Horak (Bull. Astron. Inst. Csl., 26, 257, 1975) and H.E. Jorgensen (A&A, 44, 459, 1975) who gives i = 83 (approx.) and the fractional luminosity of the brighter star as 0.51 (in yellow).

540. A recently discovered, interesting, and massive system. Thackeray pointed out its similarity to img src="http://www.chara.gsu.edu/icons/iota.gif"> Ori and HD 37756. He stated that the two spectra are clearly unequal in intensity. The system is being observed photometrically to find out if there are any eclipses.

541. Lucy & Sweeney adopt a circular orbit.

542. The epoch is primary minimum (defined as the eclipse of the more massive star, since the two eclipses are almost equal in depth). The orbit was assumed circular, in accordance with the light-curve. Values of V derived from each component are slightly, but not significantly, different. The star was identified as an eclipsing and spectroscopic binary by T.D. Kinman (MNASSA, 19, 62, 1960), but only with the appearance of the paper by Bell & Malcolm has a reliable orbit become available. The paper includes photometric observations and analysis. The orbital inclination is found to be close to 89. The less massive component gives about 0.89 of the light of the more massive (in V). The system is believed to be in contact, or nearly so. The period has been constant for at least 25 years.

543. Brighter component of ADS 7114: companion 9.5, currently at 4".5. The companion is itself double, and a visual orbit has been computed for the pair BC.

544. The elements given supersede those in an earlier note by Neubauer (PASP, 42, 354, 1930). The appreciable eccentricity is unusual in a system of such short period. Neubauer also drew attention to the small mass-function. A 7.5 companion at 2".7 is listed in IDS

545. Orbital elements have also been published by J.L. Greenstein & A. Saha (ApJ, 304, 721, 1986), who find an appreciably lower value of K. This is probably because they did not resolve the secondary spectrum. Latham et al. report that they can see it in the cross-correlation function, but they have made no estimate of K. Greenstein & Saha suggested that the companion of this high-velocity subdwarf - one of the few Population II binaries with determined elements - might be either a white dwarf or a subdwarf of late K or M spectral type. The detection of its spectrum by Latham et al. points towards the latter alternative.

546. Abt & Levy assumed the values of P (21.85), T, e and (adjusted to the primary component) from the most recent visual orbit by W.D. Heintz (Veröoff. Sternw. München, 7, 31, 1967). They find that their velocities and those obtained by Underhill (Pub. DAO, 12, 159, 1963) fit the predictions of Heintz' orbit quite well. Their value of V is in close agreement with Underhill's. Their preliminary value of K is higher than hers: the masses she deduced for the system were surprisingly low. The parallax is 0".074 and the inclination 134.8. P. Baize (J. Observateurs, 38, 40, 1955) gives m = 2.0. Three other companions are listed in IDS but all at large angular distances. The star was formerly known as 10 UMa, but it is no longer within the boundaries of that constellation.

547. The magnitude at maximum has been measured photoelectrically; the value given for the minimum is estimated from plots of the light-curve. The spectral types are given by Andersen & Popper as G2-G5. The epoch is primary minimum (the eclipses are almost, but not quite, equal) and the orbit is assumed circular in agreement with the light-curve. Both components show H and K emission in their spectra and the system is regarded as one of the RS CVn group, although the distortion of the light-curve is very small. It is unusual, among members of that group, in having two components that are equal in all respects, within the observational errors. Two photoelectric light-curves have been published since the appearance of the Seventh Catalogue. J. Andersen et al. (A&AS, 43, 141, 1981) have observed the binary in the uvby system and find an orbital inclination very close to 88 and that the (just) more massive component has a luminosity in y about 5 percent greater than the other. P.V. Rao & M.B.K. Sarma (Photometric and Spectroscopic Binary Systems, p. 361, 1981) observed in the UBV system. They agree with Andersen et al. on the inclination but make the primary component about 13 percent brighter (in V) than the secondary. Andersen et al. discuss the age of the binary (its high systemic velocity suggests that it is old) but they suspend judgment on the topic.

548.

549. Lucy & Sweeney adopt a circular orbit.

550. Listed by Abt & Snowden as an Si, Sr, Cr star. Elements for such a long-period low amplitude binary must be regarded as provisional until they are confirmed.

551. Andersen's observations are of higher dispersion than earlier ones by M.W. Feast (MNRAS, 114, 246, 1954). Andersen's values of K and K have been preferred over Feast's slightly smaller ones because Andersen also carefully investigated sources of systematic error. The orbit was assumed circular (since confirmed by the light-curve) and the epoch is T for the `primary' component. (The two minima are almost equal and the spectra are indistinguishable in type, but one is about ten percent stronger than the other). J. Clausen & B. Grønbech (A&A, 58, 131, 1977) have published uvby photometry of this system (upon which the spectral types given in the Catalogue are based). They find an orbital inclination just under 87 and assign equal visual magnitudes to the two components.

552. The star HD 77581 is the optical counterpart of the X-ray source 3U 0900-49 which, as one of the optically brightest known X-ray sources, has been much observed. It is impossible to list all references to the study of this system. Orbital studies include: E.J. Zuiderwijk et al. (A&A, 35, 353, 1975), L.O. Petro & W.A. Hiltner (ApJ, 190, 661, 1974), J.B. Hutchings (ApJ, 192, 685, 1974), G. Wallerstein (ApJ, 194, 451, 1974), S. Rappaport et al. (ApJ, 206, L103, 1976), J.A. van Paradijs et al. (Nature, 259, 547, 1976) and A&AS, 30, 195, 1977) and P.E. Boynton et al. (ApJ, 307, 545, 1986). The orbit of the X-ray pulsar, depending as it does on pulse timing, is very accurately determined (although, note that a sin i is the observed quantity and K the derived). The epoch is T. The orbit of the visible star is less well determined, but better determined than those of the optical counterparts of other X-ray sources. Optical values of e and are in reasonably good agreement. Since the paper cited in the Catalogue gives only the elements of the X-ray pulsar, those of the visible star have been taken from the second reference above to van Paradijs et al., except for V, which is not given by them, and comes from the paper by Rappaport et al. There is as yet no evidence for changes in . The epoch is the time at which the mean longitude of the X-ray source is 90 (in a circular orbit, that would be the time of superior conjunction). Van Paradijs et al. (1977) estimate minimum masses of 17 M (X-ray source) and 20.5 M and that the orbital inclination is certainly larger than 74.

553. Epoch is T. A large deviation from the velocity-curve is noticed just after eclipse. This may be a rotation effect. R.S. Dugan found from the light-curve (Princeton Obs. Contr., 14, 1933) that i = 85.6 and the light-ratio is about 0.07.

554. Three earlier investigations (N. Ichinohe, ApJ, 25, 318, 1907); J.A. Pearce & P. Riddle, PASP, 10, 65, 1940); and O. Struve, ApJ, 99, 210, 1944) give results in good agreement with those obtained by Aikman. The star is an Hg, Mn star.

555. The star is listed in the HD Catalogue as having a composite spectrum. It is now considered to be an Am star. The types from the K line, hydrogen lines and metallic lines are A5, F0 and F6II, respectively. Bretz reports no trace of the secondary spectrum `apparent in 4500 region'. Star is brighter component of ADS 7211: companion 10.3 at 57".2.

556. The new observations by Beavers & Salzer, revealing the presence of both spectra, supersede those of R.F. Sanford (ApJ, 55, 30, 1922) on which the previously known single-spectrum orbit was based. The new value of K is somewhat larger than Sanford's - a clear indication that he was measuring blended spectra. Beavers & Salzer find the magnitude difference of the two components (in blue) to be 1.0 (from the relative strengths of the dips in the radial-velocity traces) and they estimate that the individual spectral types are G2 and G6 to K0.

557. Epoch is T. Lucy & Sweeney adopt a circular orbit. A 6.2 companion at approximately 0".1 is listed in IDS

558. Abt & Levy use the observations obtained by R.K. Young (Pub. DAO, 2, 205, 1923) as well as their own to obtain these elements which are closely similar to those obtained by Young. Both Luyten and Lucy & Sweeney accept the reality of the orbital eccentricity. A companion at 49" is listed in IDS

559. These elements are described as preliminary by Griffin & Griffin themselves, primarily because of the limited number of observations at the node at which the velocities of the two components differ by relatively little. Nevertheless the elements of the spectroscopic orbit are in reasonable agreement with those it has in common with the interferometric orbit (W.S. Finsen, Republic Obs. Circ., 7, 116, 1966). The system has also been observed by speckle interferometry (e.g. H. McAlister ApJS, 43, 549, 1980) and, as the Griffins point out, the prospects of eventually obtaining very accurate values for the masses of the components are high. Finsen estimated m = 0; judging from the radial-velocity traces, there is a small difference in magnitude. The orbital inclination is close to 55. In IDS, two faint companions to the close pair are listed; one is 13.2 at 35".4 and the other (probably optical) is 10.6 at 222".

560. This star was formerly known as 21 Hya. After the discovery that its light varies, the star received the designation KW Hya. In some catalogues, however, it was erroneously listed as KM Hya and appears under that name in the paper by Andersen & Vaz. These authors later drew attention to the error themselves (A&A, 175, 355, 1987). The new observations supersede the orbit formerly determined by M.-T. Chauville (A&A, 40, 207, 1975). There is general agreement that the primary spectrum is an Am spectrum. Curchod & Hauck give A5, A7 and A9 from the K line, hydrogen lines and metallic lines respectively, but Andersen & Vaz favour slightly earlier types. They do not give a precise classification for the secondary spectrum, which is certainly later than the primary. The epoch is the time of primary minimum. The orbital eccentricity and time of periastron derived from the velocity-curve are in good agreement with the same quantities derived from the light-curve. The latter values are given in the Catalogue, and the other elements were derived with those quantities fixed. Andersen & Vaz have found an appreciably larger value for K than did Chauville. The value given for V is that appropriate to the primary component. The small difference in the two values of V is probably not significant. Analysis of the light-curve leads to an orbital inclination close to 88 and a difference of visual magnitude, between the components, of 1.44. Andersen & Vaz find it difficult to determine a unique evolutionary state for the two components of this system.

561. These results confirm those obtained by H.D. Curtis (Lick Obs. Bull., 4, 153, 1907). Both sets of elements were obtained from graphical solutions.

562. The minimum magnitude given is an estimate from the plot of the light-curve. The spectral classification of the primary is in disagreement with an earlier published one of A4. That of the invisible secondary is an estimate based on the photometric data. The epoch is the time of primary minimum and the orbit was assumed circular, in accordance with the light-curve. The orbital inclination is found to be 88 or 89. The fractional luminosity of the primary component (in V) is 0.98. Although the system is of short period, the two stars are believed not to be in contact.

563. Elements regarded as provisional by Harper. Later (Pub. DAO, 6, 225, 1935) he revised P to 15.990 and T to J.D. 2,420,750.851.

564. Some of these spectra had earlier been used by J. Lunt to determine orbital elements which were not published. In IDS an 11.0 companion is listed at 1".6.

565. The orbit was assumed circular after an elliptical solution showed no great improvement in the representation of the observations. The epoch is T. The star is probably a giant. There is an unusually large scatter (for photoelectric measures) of observations near the ascending node in phase.

566. The orbit was assumed circular and the epoch is T. The star is the brighter component of ADS 7348 A. The companion is 8.5 at 1".4.

567. Although the elements were determined by a graphical method, their values seem to be fairly well established. W. Buscombe & P.M. Morris (MNRAS, 121, 263, 1960) obtained five new spectrograms, and suggest the following modifications to the elements: P = 116.776, T = J.D. 2,416,456.66 and = 92.60.

568. The orbit is assumed circular and the epoch is T. The elements given are derived from the base of the He II emission lines. Somewhat different values (even for the period) are derived from the peak. Cowley et al. estimate that the secondary star is a G-type giant of approximately solar mass.

569. The orbit is assumed circular and the epoch is T. The spectroscopic observations are few and heterogeneous, and were not made by Raveendran et al. The period is derived photometrically and the star probably belongs to the RS CVn group.

570. This is a W-type W UMa system that has not previously been observed spectroscopically. The epoch is the time of primary minimum as given by B.B. Bookmyer & D.R. Faulkner (PASP, 90, 307, 1978). However, King & Hilditch found it necessary to add 0.05 to the phases of their observations to bring them into agreement with the light-curve, which indicates that the period has changed in the intervening years. The velocities were determined by cross-correlation from Reticon observations. No solution of the light-curve appears to be available.

571. Coverage of the velocity curve is very sketchy, but P (116.85), T, e and are assumed from the visual orbit by P. Muller (Bull. Astron. Paris, 21, 131, 1957) for which i = 64.5. The system is ADS 7390.

572. Both components have Am spectra classed as A1 from the ratio of Ca to H lines, and F0 from the metallic lines. There must be some difference in temperature between the stars, however, since Heard & Hurkens found m = 0.38 from the Fe I lines, and m = 0.23 from the Fe II lines. The secondary star is thus the hotter. The other point of interest about the sys tem is that it has largest minimum masses of any known system containing Am stars.

573. Orbital elements have also been published by A.H. Joy (ApJ, 64, 287, 1926). Joy thought he could detect the secondary spectrum, but Popper could detect only its effect on the wings of the lines of the primary component's spectrum. The value of V is uncertain because of uncertainty about the wave-lengths to adopt. Epoch is T computed from Popper's time of minimum. The magnitude of 6.28 at maximum is given by Popper on the V-scale. The range is estimated from his light-curve. The spectral type of the secondary star is an approximate estimate from the photometric data. A.R. Hogg & P.W.A. Bowe (MNRAS, 110, 373, 1949) found from their photoelectric light-curve that i = 70.1 and the light-ratio is approximately 0.3. Quite similar results were obtained from the same photometric observations by G. Russo et al. (A&AS, 47, 211, 1982) who pointed out, however, that the radii derived are larger than for main-sequence stars. They suggest that new spectroscopic observations are needed. The system is an X-ray source (R.G. Cruddace & A.K. Dupree, ApJ, 277, 263, 1984).

574. Griffin suggests that the spectrum is probably K2 III (consistent with the observed colours).

575. Brightest component of ADS 7438: B is 8.0 at 24".7. Component C, 8.7 at 117".8, does not share the proper motion of A. Epoch is T.

576. Griffin believes the star to be a giant (there is no known luminosity classification) and suggests that the invisible secondary spectrum is that of an F or G dwarf.

577. The spectrum has also been classified as A2 (G. Hill et al., MemRAS, 75, 131, 1975). The epoch is T and the orbit was assumed circular - as it is now demonstrated to be by the light-curve. Early attempts to analyze the light-curve ran into difficulties (R.E. Wilson, AJ, 70, 368, 1965). Solutions could be obtained only by postulating an extended atmosphere or third light. P. Broglia & P. Conconi (A&AS, 27, 285, 1977) - the magnitudes in the Catalogue were taken from this paper) were able to solve their new BV light-curves by the Wilson-Devinney method without the help of such hypotheses. They find that the secondary (probably of mid-G spectral type) fills its Roche lobe, that the orbital inclination is close to 84 and the fractional luminosity (in V) of the primary star is about 0.94. These results were confirmed by F. Mardirossian et al. (A&AS, 27, 285, 1977).

578. Epoch is T: orbit assumed circular. Four-colour photoelectric observations by H.L. Johnson (ApJ, 131, 127, 1960) yield i = 85.17, m = 4.85. Magnitudes given in catalogue are based on Johnson's V observations. A new study of Johnson's infrared light-curve by G. Giuricin, F. Mardirossian & F. Predolin (IBVS, No. 1786, 1980) does not significantly change these results.

579.

580. Epoch is T: eccentricity is less than 0.02 and was assumed to be zero. Very similar values for the elements were published by W. Zurhellen (ANac, 173, 353, 1907). Plummer emphasizes the difficulties of measurement arising from the superposition of two spectra (the composite nature of the spectrum is the result of the blending of the spectra of the spectroscopic-binary components). The close agreement between Plummer's results and Zurhellen's, however, suggests that the elements are reasonably well determined. New observations by S.B. Parsons (ApJS, 53, 553, 1983) confirm these elements and justify the b rating. Parsons points out that the values of K and K were ascribed the wrong way around in the Seventh Catalogue. As is to be expected, the A-type star has the larger amplitude. He also gives T 0.21 earlier. Star is brighter member of ADS 7480: this pair, however, appears to be optical.

581. Earlier spectroscopic observations have been published by W.S. Adams & A.H. Joy (ApJ, 49, 189, 1919), O. Struve & H.G. Horak (ApJ, 112, 178, 1950), D.M. Popper (PASP, 62, 115, 1950), L. Binnendijk (Pub. DAO, 13, 27, 1967) and S.P. Worden & J.A.J. Whelan (MNRAS, 163, 391, 1973). It is difficult to choose between the last of these and McLean's results. On the one hand, McLean's observations are of higher dispersion; on the other, as he himself points out, Worden & Whelan made more observations at higher time-resolution. The differences are not great. That in V, if significant, is probably only a systematic error. The two values of K are nearly identical. McLean's somewhat lower value of K brings his determination of the mass-ratio somewhat closer to the photometric values; his elements have been preferred largely on this account. The orbit is assumed circular, in accord with the light-curve, and the epoch is the time of eclipse of the less massive component as deduced from the phases given by McLean. There is some evidence of variable emission in the K line. As already mentioned, synthetic light-curves (S. Mochnacki, BAAS, 4, 339, 1972), J.B. Hutchings & G. Hill ApJ, 179, 539, 1973) lead to a lower mass-ratio than is found spectroscopically. This is further confirmed by R.W. Hilditch (MNRAS, 196, 305, 1981). A full discussion of the difficulties of analyzing the light-curve of this system has been published by A.P. Linnell (ApJ, 316, 305, 1987), who criticizes the hypothesis of starspots as an explanation of some features of the light-curves. There seems general agreement that the orbital inclination is somewhat in excess of 80, although lower values have been published (P.G. Niarchos, Ap&SS, 58, 301, 1978), S.R. Jabbar & Z. Kopal, ibid., 92, 99, 1983). Hutchings & Hill ascribe 0.59 of the total light to the primary component. The system is the brighter member of ADS 7494: the companion, probably optical, is 13.1 at 7".0. Worden & Whelan found that BD +55 1351 has the same radial velocity as the centre of mass of W UMa, while O.J. Eggen (MemRAS, 70, 117, 1967) has suggested that these two stars share a common proper motion. The system is an X-ray source (R.G. Cruddace & A.K. Dupree, ApJ, 277, 263, 1984).

582. The minimum magnitude is estimated from a plot of the light-curve by A. Okazaki (PASJ, 29, 289, 1977). The spectrum may be as late as A3 (G. Hill et al., MemRAS, 71, 131, 1975). Epoch is T and the orbit was assumed circular. Okazaki obtained eleven coudé spectrograms, but he did not publish new elements, noting that his measures of radial velocity agreed with Struve's velocity curve. (Therefore, we have upgraded the quality from e to d). Okazaki estimates that the secondary spectrum is about G5 and finds that the system is not an undermassive `R CMa' system. His light-curve yields an inclination of 86 and a fractional luminosity (in V) for the primary of 0.87. Similar results were obtained from the same observations by B. Cester et al. (A&AS, 36, 273, 1979).

583. Although this star has been known for a long time to have a variable velocity (J.S. Plaskett et al., Pub. DAO, 1, 163, 1920), this is the first set of orbital elements published for it. The epoch is T for the primary component and the orbit was assumed to be circular. The star is a visual binary (Kui 44); the separation of the two components is about 0".4 and has apparently remained unchanged for forty years. One component is the two-spectra binary and the other is a Sct variable. The V magnitude of the entire system varies by about 0.2. According to Fekel & Bopp all three components are of the same spectral type (A8 IV) and of nearly equal luminosity. The members of the close pair may show some marginal Am characteristics in their spectra. The coverage of the velocity curve is not complete, and this accounts for the relatively low grade assigned to the elements.

584. The orbit is assumed circular and the epoch is T. Carquillat et al. estimate that the invisible secondary spectrum is at least as late as K1 and that the orbital inclination is greater than 27. These elements have been in a large measure confirmed by D.W. Latham et al. (AJ, 96, 567, 1988).

585. Preliminary results were published by Popper (ApJ, 109, 100, 1949). Binary nature of star was discovered by Shajn (Pulkovo Obs. Circ., No. 2, 1932). Elliptical elements were also derived in the paper by Popper & Shajn, and e was found to be 0.014. Epoch is T. Popper states that his contribution to the paper was limited to supplying Shajn with the Yerkes spectrograms.

586. This is a system of the U Gem type and the motion of the white-dwarf component can be determined only from measures of the H emission. The orbit is assumed circular and the epoch is the time of inferior conjunction of the emission-line source. Coverage of the velocity-curve is good, but the scatter of individual observations is large. No absolute value is given for the systemic velocity.

587. Luyten's recomputation is preferred to the orbital elements derived by H.S. Jones, from these same observations (Cape Annals, 10, pt. 8, 53, 1938), because Jones had to fix T. Epoch given is T.

588. Despite the appreciable orbital eccentricity, the epoch is the time of primary minimum. The values of e and were fixed at those obtained from the light-curve. The system displays apsidal motion with a period of 354 years. The orbital inclination is found to be nearly 36, and the stars are estimated to differ by 0.3 in V.

589. The new elements supersede the original orbit by W.E. Harper (Pub. DAO, 3, 194, 1925) and the later one by Abt & Levy (ApJS, 30, 273, 1976) primarily because Batten & Morbey succeeded in measuring the secondary spectrum. Although the new elements of the primary differ little from those derived by Abt & Levy, the new observations made it possible to reconcile all available observations on one period. A circular orbit was adopted, after consideration of both circular and elliptical solutions, and the epoch is T. Batten & Morbey estimated from spectrophotometry that V = 0.92 and that the secondary spectrum is approximately G0. These results are consistent with the small trigonometrical parallax of 0".038.

590. The magnitude may be slightly variable and there are discordant spectral (and luminosity) classifications in the literature. In particular, O.J. Eggen (ApJS, 55, 597, 1984) gives B9 III. The orbital elements are derived from a heterogeneous set of observations and slightly different values can be found for each element (including the period) for different selections of the observations to be used. In particular, because of differences between observatories, the value of V is highly uncertain.

591. This RS CVn binary (not yet known to eclipse) was recognized as a single-spectrum binary by C.T. Bolton et al. (AJ, 86, 1267, 1981) who derived orbital elements and found a discrepancy between their photometry of the system and the trigonometric parallax. Barden showed that the spectrum exhibits three sets of lines although there is, as yet, no orbit for the third body. The presence of the third body can account for discrepancy found by Bolton et al. The orbit was assumed circular and the epoch is T for the primary as determined by Bolton et al. There is some evidence of a small phase difference between the two sets of observations. Barden gives the spectral type of the secondary as `late K or M0 dwarf' and the third component is similar.

592. See note for No. 469.

593. Two recent studies supersede that by O. Struve & V. Zebergs (ApJ, 130, 137, 1959). The other is by B.J. Hrivnak et al. (ApJ, 285, 683, 1984). This and Barden's study are of similar quality. The sums of K and K from the two investigations are nearly similar, but the mass-ratio is different, and the work of Hrivnak et al. may have been affected by the lines of the spectra of the companion (see next note). The epoch is T and the orbit was assumed circular. The minimum magnitude given is an estimate based on the eclipse depth. Four recent photometric analyses (B. Hrivnak, ApJ, 290, 696, 1985), J. Kaluzny & G. Pojmânski, Acta Astron., 33, 277, 1983), R.W. Hilditch, MNRAS, 196, 305, 1981) and R.H. Koch & C.R. Shanus, AJ, 83, 1452, 1978) agree on an orbital inclination around 67. The last named also give V = 0.2. All these results, however, were obtained before the discovery of the companion which is the subject of the next note. Spectral types assigned to this system and the next must necessarily be imprecise. The system is an X-ray source (R.G. Cruddace & A.K. Dupree, ApJ, 277, 263, 1984).

594. The contact binary XY Leo has long been known to display period changes that were apparently themselves periodic. A third body has often been suspected, but never detected until Barden found the lines of two other spectra in the combined light of the system and derived orbital elements for another short-period pair. The presumption is therefore strong that these two pairs are revolving around their common centre of mass in about 20 years. Emission features at H and H and K are ascribed by Barden to this second binary which he believes to be of the BY Dra type. The orbit is assumed circular and the epoch is the time of superior conjunction of the primary component. Barden gives no direct estimate of the magnitude of the companion, which is not seen separately from the contact binary and the spectral types are estimates based on masses derived from an assumed orbital inclination (31) for the new pair. Barden believes the orbits in the quadruple system are not coplanar.

595. See note for No. 469. A shorter period is also possible. An 11.5 companion at 9".1 is listed in IDS

596. The observations are few and define only the nodes of the velocity-curves. The epoch is the time of primary minimum and the orbit is assumed circular. Since McLean & Hilditch were not explicit about the ephemeris used, we have adopted that given by G. Hill (Pub. DAO, 15, 297, 1979). He found an orbital inclination close to 80 and that the primary gives about five times as much light as the secondary.

597. See note for No. 469. Other periods are still possible. Two companions are listed in IDS: 13.8 at 16".6 and 10.2 at 22".4

598. The orbit is assumed circular and the epoch is the time of inferior conjunction of the emission-line source. The period is uncertain, a value of 0.525 is still possible. The primary spectrum shows only emission lines of hydrogen, helium and ionized calcium. There are absorption lines that appear to come from the secondary spectrum and correspond to K ~ 70 km/sec. Thorstensen estimates that the secondary component has a K or very early M spectral type and contributes about 30 percent of the light at 5893. The system is a weak X-ray source.

599. See note for No. 469. Other periods are possible.

600. This is another system of the U Gem type, which was shown to be an eclipsing variable with one of the shortest known periods by N. Vogt (IAU Circ. No. 3357, 1979). The epoch is the time of primary minimum and the orbit was assumed circular. The only features in the spectrum are double emission peaks, of hydrogen and helium, flanking a central absorption. The value given for K is an approximate mean of that derived from each set of peaks and the absorptions separately. The value of V is approximately that derived from the central absorption. H. Ritter (A&A, 85, 362, 1980) derives an orbital inclination of 76 from the light-curve. N. Vogt et al. (A&A, 94, L29, 1981) also discuss the light-curve.