5,859 research outputs found
A Three-Term Conjugate Gradient Method with Sufficient Descent Property for Unconstrained Optimization
Conjugate gradient methods are widely used for solving large-scale unconstrained optimization problems, because they do not need the storage of matrices. In this paper, we propose a general form of three-term conjugate gradient methods which always generate a sufficient descent direction. We give a sufficient condition for the global convergence of the proposed general method. Moreover, we present a specific three-term conjugate gradient method based on the multi-step quasi-Newton method. Finally, some numerical results of the proposed method are given
Elastic Differential Cross Sections for Space Radiation Applications
The eikonal, partial wave (PW) Lippmann-Schwinger, and three-dimensional
Lippmann- Schwinger (LS3D) methods are compared for nuclear reactions that are
relevant for space radiation applications. Numerical convergence of the eikonal
method is readily achieved when exact formulas of the optical potential are
used for light nuclei (A 16), and the momentum-space representation of
the optical potential is used for heavier nuclei. The PW solution method is
known to be numerically unstable for systems that require a large number of
partial waves, and, as a result, the LS3D method is employed. The effect of
relativistic kinematics is studied with the PW and LS3D methods and is compared
to eikonal results. It is recommended that the LS3D method be used for high
energy nucleon-nucleus reactions and nucleus-nucleus reactions at all energies
because of its rapid numerical convergence and stability
A Third Planet Orbiting HIP 14810
We present new precision radial velocities and a three-planet Keplerian orbit
fit for the V = 8.5, G5 V star HIP 14810. We began observing this star at Keck
Observatory as part of the N2K Planet Search Project. Wright et al. (2007)
announced the inner two planets to this system, and subsequent observations
have revealed the outer planet planet and the proper orbital solution for the
middle planet. The planets have minimum masses of 3.9, 1.3, and 0.6 M_Jup and
orbital periods of 6.67, 147.7, and 952 d, respectively. We have numerically
integrated the family of orbital solutions consistent with the data and find
that they are stable for at least 10^6 yr. Our photometric search shows that
the inner planet does not transit.Comment: ApJL, accepte
The Sunshine of Paradise Alley
https://digitalcommons.library.umaine.edu/mmb-vp/6609/thumbnail.jp
I Love You In The Same Old Way : Darling Sue
https://digitalcommons.library.umaine.edu/mmb-vp/1676/thumbnail.jp
The Sunshine of Paradise Alley
https://digitalcommons.library.umaine.edu/mmb-vp/6610/thumbnail.jp
Retired A Stars and Their Companions VI. A Pair of Interacting Exoplanet Pairs Around the Subgiants 24 Sextanis and HD200964
We report radial velocity measurements of the G-type subgiants 24 Sextanis
(=HD90043) and HD200964. Both are massive, evolved stars that exhibit periodic
variations due to the presence of a pair of Jovian planets. Photometric
monitoring with the T12 0.80m APT at Fairborn Observatory demonstrates both
stars to be constant in brightness to <= 0.002 mag, thus strengthening the
planetary interpretation of the radial velocity variations. 24 Sex b,c have
orbital periods of 453.8 days and 883~days, corresponding to semimajor axes
1.333 AU and 2.08 AU, and minimum masses (Msini) 1.99 Mjup and 0.86 Mjup,
assuming a stellar mass 1.54 Msun. HD200964 b,c have orbital periods of 613.8
days and 825 days, corresponding to semimajor axes 1.601 AU and 1.95 AU, and
minimum masses 1.85 Mjup and 0.90 Mjup, assuming M* = 1.44 Msun. We also carry
out dynamical simulations to properly account for gravitational interactions
between the planets. Most, if not all, of the dynamically stable solutions
include crossing orbits, suggesting that each system is locked in a mean motion
resonance that prevents close encounters and provides long-term stability. The
planets in the 24 Sex system likely have a period ratio near 2:1, while the
HD200964 system is even more tightly packed with a period ratio close to 4:3.
However, we caution that further radial velocity observations and more detailed
dynamical modelling will be required to provide definitive and unique orbital
solutions for both cases, and to determine whether the two systems are truly
resonant.Comment: AJ accepte
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