Spin-Orbit Alignment for the Circumbinary Planet Host Kepler-16 A

Kepler-16 is an eccentric low-mass eclipsing binary with a circumbinary transiting planet. Here, we investigate the angular momentum of the primary star, based on Kepler photometry and Keck spectroscopy. The primary star’s rotation period is 35.1 ± 1.0 days, and its projected obliquity with respect to the stellar binary orbit is 1°.6 ± 2°.4. Therefore, the three largest sources of angular momentum—the stellar orbit, the planetary orbit, and the primary’s rotation—are all closely aligned. This finding supports a formation scenario involving accretion from a single disk. Alternatively, tides may have realigned the stars despite their relatively wide separation (0.2 AU), a hypothesis that is supported by the agreement between the measured rotation period and the “pseudosynchronous” period of tidal evolution theory. The rotation period, chromospheric activity level, and fractional light variations suggest a main-sequence age of 2–4 Gyr. Evolutionary models of low-mass stars can match the observed masses and radii of the primary and secondary stars to within about 3%

Development and Validation of an Electric Submersible Pump Bearing Erosion Facility That Replicates the Conditions Experienced During Pump Operation

The ever increasing global oil demand has forced the energy industry to provide artificial stimulation to many oil wells to increase their productivity. A common way to do this is to install an electric submersible pump (ESP) in the wellbore to overcome the pressure losses associated with bringing hydrocarbons to the surface for processing. This type of artificial lift has become increasingly more popular in offshore oil fields. When an ESP fails in a subsea well, the cost to replace it has been estimated to be as much as forty times the cost of the pump due to the high price of offshore rig time. The increase in deep water oil production over the past two decades has demanded that ESPs operate properly for as long as possible. One of the most common failure modes for ESPs arises from erosion by sediments (fine sand) in the flow. The journal bearings in the ESP are susceptible to erosion from these particles because the pump bearings are lubricated by the fluid flowing through the pump. Previous ESP erosion tests that were conducted at the Turbomachinery Laboratory at Texas A&M University show that the erosion caused by sand particles in the flow lead to ESP journal bearing erosion that ultimately caused the pump to fail. This work provides the design, construction, and validation of a testing apparatus that was built to replicate a single ESP stage so that journal bearings can be eroded and evaluated to be used to design new bearings with a longer lifetime. The testing apparatus is capable of replicating the conditions of an ESP to conduct erosion studies on a journal bearing independent of the actual pump. This provides a cost effective way to test different bearing materials over a variety of different operating conditions. The testing apparatus is capable of operating speeds up to 7200 RPM, gas volume fractions (GVF) ranging from 0-100%, and different testing liquids (water or oil). The testing apparatus was designed to collect bearing annulus dynamic pressure, temperature, and the radial loads the bearing experiences as well as measure the orbital displacement of the bearing. In addition, the bearing geometry can be measured and the surface can be observed at discrete time intervals

Earthquake Arrival Association with Backprojection and Graph Theory

The association of seismic wave arrivals with causative earthquakes becomes progressively more challenging as arrival detection methods become more sensitive, and particularly when earthquake rates are high. For instance, seismic waves arriving across a monitoring network from several sources may overlap in time, false arrivals may be detected, and some arrivals may be of unknown phase (e.g., P- or S-waves). We propose an automated method to associate arrivals with earthquake sources and obtain source locations applicable to such situations. To do so we use a pattern detection metric based on the principle of backprojection to reveal candidate sources, followed by graph-theory-based clustering and an integer linear optimization routine to associate arrivals with the minimum number of sources necessary to explain the data. This method solves for all sources and phase assignments simultaneously, rather than in a sequential greedy procedure as is common in other association routines. We demonstrate our method on both synthetic and real data from the Integrated Plate Boundary Observatory Chile (IPOC) seismic network of northern Chile. For the synthetic tests we report results for cases with varying complexity, including rates of 500 earthquakes/day and 500 false arrivals/station/day, for which we measure true positive detection accuracy of > 95%. For the real data we develop a new catalog between January 1, 2010 - December 31, 2017 containing 817,548 earthquakes, with detection rates on average 279 earthquakes/day, and a magnitude-of-completion of ~M1.8. A subset of detections are identified as sources related to quarry and industrial site activity, and we also detect thousands of foreshocks and aftershocks of the April 1, 2014 Mw 8.2 Iquique earthquake. During the highest rates of aftershock activity, > 600 earthquakes/day are detected in the vicinity of the Iquique earthquake rupture zone

Giant Planet Occurrence in the Stellar Mass-Metallicity Plane

Correlations between stellar properties and the occurrence rate of exoplanets can be used to inform the target selection of future planet search efforts and provide valuable clues about the planet formation process. We analyze a sample of 1194 stars drawn from the California Planet Survey targets to determine the empirical functional form describing the likelihood of a star harboring a giant planet as a function of its mass and metallicity. Our stellar sample ranges from M dwarfs with masses as low as 0.2 Msun to intermediate-mass subgiants with masses as high as 1.9 Msun. In agreement with previous studies, our sample exhibits a planet-metallicity correlation at all stellar masses; the fraction of stars that harbor giant planets scales as f \propto 10^{1.2 [Fe/H]}. We can rule out a flat metallicity relationship among our evolved stars (at 98% confidence), which argues that the high metallicities of stars with planets are not likely due to convective envelope "pollution." Our data also rule out a constant planet occurrence rate for [Fe/H]< 0, indicating that giant planets continue to become rarer at sub-Solar metallicities. We also find that planet occurrence increases with stellar mass (f \propto Mstar), characterized by a rise from 3.5% around M dwarfs (0.5 Msun) to 14% around A stars (2 Msun), at Solar metallicity. We argue that the correlation between stellar properties and giant planet occurrence is strong supporting evidence of the core accretion model of planet formation.Comment: Fixed minor typos, modified the last paragraph of Section

A Third Exoplanetary System with Misaligned Orbital and Stellar Spin Axes

We present evidence that the WASP-14 exoplanetary system has misaligned orbital and stellar-rotational axes, with an angle lambda = 33.1 +/- 7.4 deg between their sky projections. The evidence is based on spectroscopic observations of the Rossiter-McLaughlin effect as well as new photometric observations. WASP-14 is now the third system known to have a significant spin-orbit misalignment, and all three systems have "super-Jupiter" planets (M_P > 3 Mjup) and eccentric orbits. This finding suggests that the migration and subsequent orbital evolution of massive, eccentric exoplanets is somehow different from that of less massive close-in Jupiters, the majority of which have well-aligned orbits.Comment: 8 pages, 5 figures, 3 tables, PASP accepte