A study of the close binary star TU Monocerotis

New photometric elements,i=89°.5,r _a =0.24,r _b =0.25 andL _a =0.82(Y), 0.88(B), 0.94(U), are deduced for the eclipsing system TU Mon, using the incomplete Fourier method for the analysis of its light curve. They are based upon three-colour photoelectric observations obtained in 1966–68 with the 36-inch reflector of the Okayama Astrophysical Observatory. From discussion combined with the spectroscopic data byDeutsch (1945) and byPopper (1967), it seems fair to conclude that TU Mon is an ordinary semi-detached close binary system consisting of a detached brighter B5V star and an A5 subgiant in contact at its Roche limit.     

UBV observations of the eclipsing binary FW Monocerotis

Photoelectric observations of FW Monocerotis inU,B, andV filters have been discussed. The depths of the primary minimum inU BV colours are 2 _. ^m 63, 2 _. ^m 17 and 1 _. ^m 76, respectively. No variation in the period has been found and its revised value is 3 _. ^d 8735868.     

A new determination of the orbit and masses of the Be binary system δ Scorpii

The binary star δ Sco (HD143275) underwent remarkable brightening in the visible in 2000, and continues to be irregularly variable. The system was observed with the Sydney University Stellar Interferometer (SUSI) in 1999, 2000, 2001, 2006 and 2007. The 1999 observations were consistent with predictions based on the previously published orbital elements. The subsequent observations can only be explained by assuming that an optically bright emission region with an angular size of  ≳2 ± 1 mas  formed around the primary in 2000. By 2006/2007 the size of this region grew to an estimated ≳4 mas.
We have determined a consistent set of orbital elements by simultaneously fitting all the published interferometric and spectroscopic data as well as the SUSI data reported here. The resulting elements and the brightness ratio for the system measured prior to the outburst in 2000 have been used to estimate the masses of the components. We find   M_A = 15 ± 7 M_⊙  and   M_B = 8.0 ± 3.6 M_⊙  . The dynamical parallax is estimated to be  7.03 ± 0.15 mas  , which is in good agreement with the revised Hipparcos parallax.     

Absolute dimensions of the close binary systems V453 Monocerotis and V523 Cassiopeiae

We present multi-colour CCD observations of the low-temperature contact binaries, V453 Mon and V523 Cas. Their light curves are modelled to determine a new set of stellar and orbital parameters. Analysis of mid-eclipse times yields a new linear ephemeris for both systems. A period decrease (dP/dt=2.3×10⁻⁷ days/yr) in V453 Mon is discovered. V523 Cas, however, is detected to show a period increase (dP/dt=9.8×10⁻⁸ days/yr) because of the mass transfer of a rate of 1.1×10⁻⁷ M_⊙ yr⁻¹, from a less massive donor. Using these findings we can determine the physical parameters of the components of V523 Cas to be M ₁=0.76 (3)M _⊙, M ₂=0.39 (2)M _⊙, R ₁=0.74 (2)R _⊙, R ₂=0.55 (2)R _⊙, L ₁=0.19 (3)L _⊙, L ₂=0.14 (3)L _⊙, and the distance of system as 46(9) pc.     

The determination of a spectroscopic binary orbit

An efficient analytical method for determining the orbit of spectroscopic binary is presented. The advantages of the method are: (1) its accuracy, (2) its rapidity, (3) the possibility of making adjustments in the elements before the final presentation. This method seems to have very definite advantages in comparison to the other methods. It gives a standard set of velocity curves also, for a set of (e, ) values with amplitude ranging between +1 K and –1 K. These curves in tabulated, or graphical form can be used in routine fashion for the determination of preliminary elements preparatory to a least-squares correction. Application to the velocity curve of o And and Ori is given.     

A new method of initial orbit determination

Up to now we have been dealing with the construction of entirely analytical planetary theories such as VSOP82 (Bretagnon, 1982) and TOP82 (Simon, 1983). These theories take into account the whole of the Newtonian perturbations of nine point masses: the Sun, the Earth-Moon barycentre, the planets Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune. They also take into account perturbations due to some minor planets, to the action of the Moon and the relativistic effects. The perturbations of these last three types are in a very simple way under analytical form but they considerably increase the computations when introduced in the numerical integration programs.In the present paper we thus study a solution in which the Newtonian perturbations for the ten point masses are treated through numerical integration, the other perturbations being analytically added.     

The orbit of the nearby low-mass binary Gliese 600

We have computed a combined spectroscopic-interferometric orbit for the nearby binary Gliese 600 discovered by us. The orbital period is 2.78 years, and the semimajor axis is 100 mas (0.1″). Its M0 V components are almost identical and have a mass of 0.5M _⊙. The mass ratio is uncertain because of the low radialvelocity semiamplitude (7 km s^?1) associated with the low orbital inclination (37°). The orbital parallax of the binary (52±11 mas) matches its dynamical and photometric parallaxes but differs significantly from the Hipparcos parallax (44.3±1.6) mas; the latter was probably distorted by the orbital motion that was not taken into account.     

A spectroscopic orbit for the two—Spectrum eclipsing binary RT Persei

Intensified Reticon spectra have been obtained at a high dispersion for the Algol system, RT Persei. They were measured by the cross-correlation technique. The spectroscopic elements, revised for the primary component and determined for the secondary for the first time, are: T₀ = HJD 2,446,038.9332, K₁ = 55.0, K₂ = 194.7, V₀ = −8.3 km/s. A mass ratio q = m₂/m₁ = 0.282 is deduced. A circular orbit is adopted. The spectrum of the primary is F5V, and the secondary is a subgiant. With the elements determined here and the published photometric parameters, the absolute dimensions of the binary are: A = 4.20, R₁ = 1.20, R₂ = 1.08 R; M₁ = 1.08, M₂ = 0.30 M.     

Analysis of the orbit of ariel 1, 1962-15A,near 15th-order resonance

Ariel 1, the first international satellite, was launched on 26 April 1962, into an orbit inclined at 53.85° to the equator, with an initial perigee height near 390 km. On 8 May 1973 the orbit passed through 15th-order resonance and has been determined, with the RAE orbit refinement program PROP, at eight epochs between February and August 1973 using 500 observations.The orbital inclinations during the time of 15th-order resonance, as given by these eight orbits and 31 U.S. Navy orbits, were fitted with a theoretical curve using the THROE computer program, the best fit giving $\text{10}{}^9\text{C}\text{?}{}_{15}\text{= ?370 ± 14}$ and 10⁹S₁₅ = ?114 ± 31.The values of eccentricity were also successfully fitted using THROE, and the results are discussed.     

The orbit of the double-line spectroscopic binary system HR 7112

We present velocity observations, obtained with the E. W. Fick Observatory 0.6 m telescope, of the 7th magnitudeK1 star HR 7112. Our observations show that HR 7112 is a double-line spectroscopic binary system composed of almost equal mass stars with a period of 215.6 days. The orbit has an eccentricitye = 0.142 and the stars orbit each other with a mean semi-major axis distance of approximately 0.4sin(i) AU. The masses of the stars are consistent with the classification as giant stars. Tidal effects are known to circularise the orbits of giant stars and this process is apparently underway in this system.     

A new approach to impulsive rendezvous near circular orbit

A new approach is presented for the problem of planar optimal impulsive rendezvous of a spacecraft in an inertial frame near a circular orbit in a Newtonian gravitational field. The total characteristic velocity to be minimized is replaced by a related characteristic-value function and this related optimization problem can be solved in closed form. The solution of this problem is shown to approach the solution of the original problem in the limit as the boundary conditions approach those of a circular orbit. Using a form of primer-vector theory the problem is formulated in a way that leads to relatively easy calculation of the optimal velocity increments. A certain vector that can easily be calculated from the boundary conditions determines the number of impulses required for solution of the optimization problem and also is useful in the computation of these velocity increments. Necessary and sufficient conditions for boundary conditions to require exactly three nonsingular non-degenerate impulses for solution of the related optimal rendezvous problem, and a means of calculating these velocity increments are presented. A simple example of a three-impulse rendezvous problem is solved and the resulting trajectory is depicted. Optimal non-degenerate nonsingular two-impulse rendezvous for the related problem is found to consist of four categories of solutions depending on the four ways the primer vector locus intersects the unit circle. Necessary and sufficient conditions for each category of solutions are presented. The region of the boundary values that admit each category of solutions of the related problem are found, and in each case a closed-form solution of the optimal velocity increments is presented. Similar results are presented for the simpler optimal rendezvous that require only one-impulse. For brevity degenerate and singular solutions are not discussed in detail, but should be presented in a following study. Although this approach is thought to provide simpler computations than existing methods, its main contribution may be in establishing a new approach to the more general problem.     

A new orbit of Comet 1961 V (Wilson-Hubbard)

A definitive orbit of Comet 1961 V (Wilson-Hubbard), based on 84 observations, is given.     

A new kind of stellar orbit in a galactic potential

Numerical integrations of a star's motion in an axisymmetric galactic potential have unveiled a new kind of orbit in the meridional plane. Especially, neutron stars can be expected to move on such orbits.     

A new outcome of binary–binary scattering

A recently discovered solution of the three-body problem represents a new possible byproduct of binary–binary scattering. This is demonstrated by an explicit example. A way of detecting the new orbit automatically is discussed, and we give estimates related to the probability of its formation.     

The eccentric orbit of the short-period eclipsing binary V 1010 Oph

Radial velocity observations of V 1010 Oph obtained at Asiago from 23 spectra combined with those published by Guinan and Koch (1977) reveal a significant eccentricity (e0.20±0.03) with a periastron angle close to 90° at 1 level. This underlines the need for a new analysis of the light curve for photometric elements.On leave from Konkoly Observatory, Budapest, Hungary     

Light-time orbit and apsidal motion of the eclipsing binary U Ophiuchi

A comprehensive period study of the times of minima observed from 1881 to 1985 has been performed. Previous interpretations of the O–C diagram based on light-time effect are confirmed. The light-time orbit of U Oph has been revised using a differential corrections procedure. We get an eccentric orbit withe=0.22±0.06,P=38.7±0.2 yr, and a mass function . In addition, our analysis has revealed short-period apsidal motion (U/P=4515±75) in a slightly eccentric close orbit (e=0.0031±0.0003), allowing a reliable determination of the density concentration coefficient,k ₂=0.0059±4. A comparison with stellar evolutionary models calculated by Jeffery (1984) yields the helium contentY=0.28±0.05 and an age of 3×10⁷ yr for the components of U Oph.     

Gravity-darkening of the secondary component of RW Monocerotis

The two near-infrared light curves of the secondary minimum of RW Monocerotis are analysed for the gravity-darkening coefficient of the distorted subgiant secondary component of later spectral type. It is found that the monochromatic gravity-darkening coefficient of the secondary component of RW Monocerotis at wavelengths of 7800 Å and 7000 Å is about twice that obtained from von Zeipel theory.     

(42355) Typhon-Echidna: Scheduling observations for binary orbit determination

We describe a strategy for scheduling astrometric observations to minimize the number required to determine the mutual orbits of binary transneptunian systems. The method is illustrated by application to Hubble Space Telescope observations of (42355) Typhon-Echidna, revealing that Typhon and Echidna orbit one another with a period of 18.971±0.006 days and a semimajor axis of 1628±29 km, implying a system mass of (9.49±0.52)×¹⁰¹⁷ kg. The eccentricity of the orbit is 0.526±0.015. Combined with a radiometric size determined from Spitzer Space Telescope data and the assumption that Typhon and Echidna both have the same albedo, we estimate that their radii are and , respectively. These numbers give an average bulk density of only , consistent with very low bulk densities recently reported for two other small transneptunian binaries.