High Orbital Eccentricities of Extrasolar Planets Induced by the Kozai Mechanism

One of the most remarkable properties of extrasolar planets is their high orbital eccentricities. Observations have shown that at least 20% of these planets, including some with particularly high eccentricities, are orbiting a component of a wide binary star system. The presence of a distant binary companion can cause significant secular perturbations to the orbit of a planet. In particular, at high relative inclinations, a planet can undergo a large-amplitude eccentricity oscillation. This so-called "Kozai mechanism" is effective at a very long range, and its amplitude is purely dependent on the relative orbital inclination. In this paper, we address the following simple question: assuming that every host star with a detected giant planet also has a (possibly unseen, e.g., substellar) distant companion, with reasonable distributions of orbital parameters and masses, how well could secular perturbations reproduce the observed eccentricity distribution of planets? Our calculations show that the Kozai mechanism consistently produces an excess of planets with very high (e >0.6) and very low (e < 0.1) eccentricities. The paucity of near-circular orbits in the observed sample cannot be explained solely by the Kozai mechanism, because, even with high enough inclinations, the Kozai mechanism often fails to produce significant eccentricity perturbations when there are other competing sources of orbital perturbations on secular timescales, such as general relativity. On the other hand, the Kozai mechanism can produce many highly eccentric orbits. Indeed the overproduction of high eccentricities observed in our models could be combined with plausible circularizing mechanisms (e.g., friction from residual gas) to create more intermediate eccentricities (e=0.1-0.6).Comment: 24 pages, 6 figures, ApJ, in press, minor changes to reflect the accepted versio

The Best Brown Dwarf Yet?: A Companion to the Hyades Eclipsing Binary V471 Tau

We have carried out an analysis of about 160 eclipse timings spanning over 30 years of the Hyades eclipsing binary V471 Tauri that shows a long-term quasi-sinusoidal modulation of its observed eclipse arrival times. The O-Cs have been analyzed for the ``light-time'' effect that arises from the gravitational influence of a tertiary companion. The presence of a third body causes the relative distance of the eclipsing pair to the Earth to change as it orbits the barycenter of the triple system. The result of the analysis of the eclipse times yields a light-time semi-amplitude of 137.2+/-12.0 s, an orbital period of P_3 = 30.5+/-1.6 yr and an eccentricity of e_3 = 0.31+/-0.04. The mass of the tertiary component is M_3 sin i_3 = 0.0393+/-0.0038 Mo when a total mass of 1.61+/-0.06 Mo for V471 Tau is adopted. For orbital inclinations i_3 > 35 deg, the mass of the third body would be below the stable hydrogen burning limit of M = 0.07 Mo and it thus would be a brown dwarf. In the next several years (near maximum elongation), it should be feasible to obtain IR images and spectra of V471 Tau C that, when combined with the known mass, age, distance, and [Fe/H], will serve as a benchmark for understanding the physical properties and evolution of brown dwarfs.Comment: 9 pages, 3 figures, accepted for publication in ApJ Letter

Scaling Bounded Model Checking By Transforming Programs With Arrays

Bounded Model Checking is one the most successful techniques for finding bugs in program. However, model checkers are resource hungry and are often unable to verify programs with loops iterating over large arrays.We present a transformation that enables bounded model checkers to verify a certain class of array properties. Our technique transforms an array-manipulating (ANSI-C) program to an array-free and loop-free (ANSI-C) program thereby reducing the resource requirements of a model checker significantly. Model checking of the transformed program using an off-the-shelf bounded model checker simulates the loop iterations efficiently. Thus, our transformed program is a sound abstraction of the original program and is also precise in a large number of cases - we formally characterize the class of programs for which it is guaranteed to be precise. We demonstrate the applicability and usefulness of our technique on both industry code as well as academic benchmarks

A planet-sized transiting star around OGLE-TR-122 - Accurate mass and radius near the Hydrogen-burning limit

We report the discovery and characterisation of OGLE-TR-122b, the smallest main-sequence star to date with a direct radius determination. OGLE-TR-122b transits around its solar-type primary every 7.3-days. With M=0.092+-0.009 Mo and R=0.120 +0.024-0.013 Ro, it is by far the smallest known eclipsing M-dwarf. The derived mass and radius for OGLE-TR-122b are in agreement with the theoretical expectations. OGLE-TR-122b is the first observational evidence that stars can indeed have radii comparable or even smaller than giant planets. In such cases, the photometric signal is exactly that of a transiting planet and the true nature of the companion can only be determined with high-resolution spectroscopy.Comment: 4 pages, 3 figures, A&A letters, in Press. Revise

Elodie metallicity-biased search for transiting Hot Jupiters I. Two Hot Jupiters orbiting the slightly evolved stars HD118203 and HD149143

We report the discovery of a new planet candidate orbiting the subgiant star HD118203 with a period of P=6.1335 days. The best Keplerian solution yields an eccentricity e=0.31 and a minimum mass m2sin(i)=2.1MJup for the planet. This star has been observed with the ELODIE fiber-fed spectrograph as one of the targets in our planet-search programme biased toward high-metallicity stars, on-going since March 2004 at the Haute-Provence Observatory. An analysis of the spectroscopic line profiles using line bisectors revealed no correlation between the radial velocities and the line-bisector orientations, indicating that the periodic radial-velocity signal is best explained by the presence of a planet-mass companion. A linear trend is observed in the residuals around the orbital solution that could be explained by the presence of a second companion in a longer-period orbit. We also present here our orbital solution for another slightly evolved star in our metal-rich sample, HD149143, recently proposed to host a 4-d period Hot Jupiter by the N2K consortium. Our solution yields a period P=4.09 days, a marginally significant eccentricity e=0.08 and a planetary minimum mass of 1.36MJup. We checked that the shape of the spectral lines does not vary for this star as well.Comment: Accepted in A&A (6 pages, 6 figures

Some Restrictions Abroad Affecting Corporations

A neutron detector concept based on solid layers of boron carbide enriched in 1 B has been in development for the last few years as an alternative for He-3 by collaboration between the ILL, ESS and Linkoping University. This Multi-Grid detector uses layers of aluminum substrates coated with (B4C)-B-10 on both sides that are traversed by the incoming neutrons. Detection is achieved using a gas counter readout principle. By segmenting the substrate and using multiple anode wires, the detector is made inherently position sensitive. This development is aimed primarily at neutron scattering instruments with large detector areas, such as time-of-flight chopper spectrometers. The most recent prototype has been built to be interchangeable with the He-3 detectors of IN6 at ILL. The 1 B detector has an active area of 32 x 48 cm(2). It was installed at the IN6 instrument and operated for several weeks, collecting data in parallel with the regularly scheduled experiments, thus providing the first side-by-side comparison with the conventional He-3 detectors. Results include an efficiency comparison, assessment of the in-detector scattering contribution, sensitivity to gamma-rays and the signal-to-noise ratio in time-of-flight spectra. The good expected performance has been confirmed with the exception of an unexpected background count rate. This has been identified as natural alpha activity in aluminum. New convertor substrates are under study to eliminate this source of background

Measurement of the Surface Gravity of η\eta Boo

Direct angular size measurements of the G0IV subgiant $\eta$ Boo from the Palomar Testbed Interferometer are presented, with limb-darkened angular size of $\theta_{LD}= 2.1894^{+0.0055}_{-0.0140}$ mas, which indicate a linear radius of $R=2.672 \pm 0.028 R_\odot$. A bolometric flux estimate of $F_{BOL} = 22.1 \pm 0.28\times 10^{-7}$ erg cm$^{-2}$s$^{-1}$ is computed, which indicates an effective temperature of $T_{EFF}=6100 \pm 28$ K and luminosity of $L = 8.89 \pm 0.16 L_\odot$ for this object. Similar data are established for a check star, HD 121860. The $\eta$ Boo results are compared to, and confirm, similar parameters established by the {\it MOST} asteroseismology satellite. In conjunction with the mass estimate from the {\it MOST} investigation, a surface gravity of $\log g=3.817 \pm 0.016$ [cm s$^{-2}$] is established for $\eta$ Boo.Comment: To appear in March 1, 2007 ApJ v657 n

A pair of planets around HD 202206 or a circumbinary planet?

Long-term precise Doppler measurements with the CORALIE spectrograph reveal the presence of a second planet orbiting the solar-type star HD202206. The radial-velocity combined fit yields companion masses of m_2\sini = 17.4 M_Jup and 2.44 M_Jup, semi-major axes of a = 0.83 AU and 2.55 AU, and eccentricities of e = 0.43 and 0.27, respectively. A dynamical analysis of the system further shows a 5/1 mean motion resonance between the two planets. This system is of particular interest since the inner planet is within the brown-dwarf limits while the outer one is much less massive. Therefore, either the inner planet formed simultaneously in the protoplanetary disk as a superplanet, or the outer Jupiter-like planet formed in a circumbinary disk. We believe this singular planetary system will provide important constraints on planetary formation and migration scenarios.Comment: 9 pages, 14 figures, accepted in A&A, 12-May-200