STARRY: Analytic Occultation Light Curves

We derive analytic, closed form, numerically stable solutions for the total flux received from a spherical planet, moon or star during an occultation if the specific intensity map of the body is expressed as a sum of spherical harmonics. Our expressions are valid to arbitrary degree and may be computed recursively for speed. The formalism we develop here applies to the computation of stellar transit light curves, planetary secondary eclipse light curves, and planet-planet/planet-moon occultation light curves, as well as thermal (rotational) phase curves. In this paper we also introduce STARRY, an open-source package written in C++ and wrapped in Python that computes these light curves. The algorithm in STARRY is six orders of magnitude faster than direct numerical integration and several orders of magnitude more precise. STARRY also computes analytic derivatives of the light curves with respect to all input parameters for use in gradient-based optimization and inference, such as Hamiltonian Monte Carlo (HMC), allowing users to quickly and efficiently fit observed light curves to infer properties of a celestial body's surface map.Comment: 55 pages, 20 figures. Accepted to the Astronomical Journal. Check out the code at https://github.com/rodluger/starr

Review of Geotechnical Investigations Resulting from the Roermond April 13, 1992 Earthquake

In 1987 the Engineering Geology section of the Delft University of Technology carried out a survey of the SE Netherlands to determine which areas were susceptible to liquefaction based on soil profile, groundwater levels and a Richter scale magnitude 6 earthquake along the principal rift fault through the Netherlands, the Peelrand fault system. The fault system has been active since the Triassic and forms part of the Rhine-North Sea rift system. The last major earthquake along the Peelrand fault was in 1933. Recently, in 1992, A 5.8 magnitude earthquake occurred at Roermond, near to the Dutch-German border. Though damage resulting from the earthquake was limited, remedial works to structures amounted to US$ 50 million in the Netherlands. The paper reviews geotechnical investigations associated with the earthquake carried out in the Netherlands. Much of the damage is attributed to liquefaction; excess pore pressures resulting from the earthquake caused sand vent eruptions, river-dyke failures and slope failures. Comparisons are made between the predictions of 1987 and that which occurred in 1992. Site investigation works are recording geotechnical and building data so as to allow for correlations between extents of damage, ground geotechnical profiles and building design. Models for liquefaction are reviewed to describe the slope failure as well as the sand vent phenomena. Densification of subsoil has been inferred from CPTs taken before and after the earthquake for some sites. Pile foundation damage has been investigated for buildings in Roermond for which their susceptibility to earthquake lateral forces in terms of stiffness and pile head working load is given

VPLanet: The Virtual Planet Simulator

We describe a software package called VPLanet that simulates fundamental aspects of planetary system evolution over Gyr timescales, with a focus on investigating habitable worlds. In this initial release, eleven physics modules are included that model internal, atmospheric, rotational, orbital, stellar, and galactic processes. Many of these modules can be coupled simultaneously to simulate the evolution of terrestrial planets, gaseous planets, and stars. The code is validated by reproducing a selection of observations and past results. VPLanet is written in C and designed so that the user can choose the physics modules to apply to an individual object at runtime without recompiling, i.e., a single executable can simulate the diverse phenomena that are relevant to a wide range of planetary and stellar systems. This feature is enabled by matrices and vectors of function pointers that are dynamically allocated and populated based on user input. The speed and modularity of VPLanet enables large parameter sweeps and the versatility to add/remove physical phenomena to assess their importance. VPLanet is publicly available from a repository that contains extensive documentation, numerous examples, Python scripts for plotting and data management, and infrastructure for community input and future development.Comment: 75 pages, 34 figures, 10 tables, accepted to the Proceedings of the Astronomical Society of the Pacific. Source code, documentation, and examples available at https://github.com/VirtualPlanetaryLaboratory/vplane

2,4,6,8-Tetra­kis(4-chloro­phen­yl)-3,7-diaza­bicyclo­[3.3.1]nonan-9-one O-benzyl­oxime acetone monosolvate

In the title compound, C38H31Cl4N3O·C3H6O, the 3,7-diaza-bicycle exists in a chair–boat conformation. The 4-chloro­phenyl groups attached to the chair form are equatorially oriented at an angle of 18.15 (3)° with respect to each other, whereas the 4-chloro­phenyl groups attached to the boat form are oriented at an angle of 32.64 (3)°. In the crystal, mol­ecules are linked by N—H⋯π and C—H⋯O inter­actions