Thermal Emission and Tidal Heating of the Heavy and Eccentric Planet XO-3b

We determined the flux ratios of the heavy and eccentric planet XO-3b to its parent star in the four IRAC bands of the Spitzer Space Telescope: 0.101% +- 0.004% at 3.6 micron; 0.143% +- 0.006% at 4.5 micron; 0.134% +- 0.049% at 5.8 micron and 0.150% +- 0.036% at 8.0 micron. The flux ratios are within [-2.2,0.3, -0.8, -1.7]-sigma of the model of XO-3b with a thermally inverted stratosphere in the 3.6 micron, 4.5 micron, 5.8 micron and 8.0 micron channels, respectively. XO-3b has a high illumination from its parent star (Fp ~(1.9 - 4.2) x 10^9 ergs cm^-2 s^-1) and is thus expected to have a thermal inversion, which we indeed observe. When combined with existing data for other planets, the correlation between the presence of an atmospheric temperature inversion and the substellar flux is insufficient to explain why some high insolation planets like TrES-3 do not have stratospheric inversions and some low insolation planets like XO-1b do have inversions. Secondary factors such as sulfur chemistry, atmospheric metallicity, amounts of macroscopic mixing in the stratosphere or even dynamical weather effects likely play a role. Using the secondary eclipse timing centroids we determined the orbital eccentricity of XO-3b as e = 0.277 +- 0.009. The model radius-age trajectories for XO-3b imply that at least some amount of tidal-heating is required to inflate the radius of XO-3b, and the tidal heating parameter of the planet is constrained to Qp < 10^6 .Comment: Accepted for publications in The Astrophysical Journa

GJ 3236: a new bright, very low-mass eclipsing binary system discovered by the MEarth observatory

We report the detection of eclipses in GJ 3236, a bright (I = 11.6) very low mass binary system with an orbital period of 0.77 days. Analysis of light- and radial velocity curves of the system yielded component masses of 0.38 +/- 0.02 and 0.28 +/- 0.02 Msol. The central values for the stellar radii are larger than the theoretical models predict for these masses, in agreement with the results for existing eclipsing binaries, although the present 5% observational uncertainties limit the significance of the larger radii to approximately 1 sigma. Degeneracies in the light curve models resulting from the unknown configuration of surface spots on the components of GJ 3236 currently dominate the uncertainties in the radii, and could be reduced by obtaining precise, multi-band photometry covering the full orbital period. The system appears to be tidally synchronized and shows signs of high activity levels as expected for such a short orbital period, evidenced by strong Halpha emission lines in the spectra of both components. These observations probe an important region of mass-radius parameter space around the predicted transition to fully-convective stellar interiors, where there are a limited number of precise measurements available in the literature.Comment: 14 pages, 5 figures, 10 tables, emulateapj format. Accepted for publication in Ap

Analysis of the World Market for Steam Coal Using a Complementarity Model

With its resource availability and the prospect of climate friendly technology, coal continues to play an important role in the global energy sector. We develop a complementarity model of the international market for steam coal. We want to analyze the level of competition in this market which is strategic for the importers' security of energy supply. In a spatial equilibrium framework, we assume the steam coal exporters to maximize their profits by choosing the optimal quantity to sell to each importing country. We compare two possible scenarios: perfect competition and Cournot competition. The results, especially the price levels, indicate that the Cournot model is not realistic, suggesting that the producing countries do not exert market power. However, the trade flows and prices observed in reality suggests that there is some form of market power with price discrimination, possibly following a Bertrand model in a spatial setting

Adaptive Cheat Detection in Decentralized Volunteer Computing with Untrusted Nodes

Part 5: Making Things Safe (Security)International audienceIn volunteer computing, participants donate computational resources in exchange for credit points. Cheat detection is necessary to prevent dishonest participants from receiving credit points, without actually providing these resources. We suggest a novel, scalable approach for cheat detection in decentralized volunteer computing systems using gossip communication. Each honest participant adapts its detection effort dynamically subject to the number of active participants, which we estimate based on observed system performance. This enables minimizing the detection overhead for each participant, while still achieving a high preselected detection rate for the overall system. Systems based on majority voting usually produce at least $$100\%$$ overhead, whereas our approach, e.g. requires only $$50.6\%$$ overhead in a network with $$1\,000$$ participants to achieve a $$99.9\%$$ detection rate. Since our approach does not require trusted entities or an active cooperation between participants, it is robust even against colluding cheaters

Measurement of pseudorapidity distributions of charged particles in proton-proton collisions at sqrt(s) = 8 TeV by the CMS and TOTEM experiments

Pseudorapidity ( $\eta$ ) distributions of charged particles produced in proton–proton collisions at a centre-of-mass energy of 8 $~\text {TeV}$ are measured in the ranges $|\eta | < 2.2$ and $5.3 < |\eta | < 6.4$ covered by the CMS and TOTEM detectors, respectively. The data correspond to an integrated luminosity of $\mathcal {L} = 45 \mu {\mathrm {b}}^{-1}$ . Measurements are presented for three event categories. The most inclusive category is sensitive to 91–96 % of the total inelastic proton–proton cross section. The other two categories are disjoint subsets of the inclusive sample that are either enhanced or depleted in single diffractive dissociation events. The data are compared to models used to describe high-energy hadronic interactions. None of the models considered provide a consistent description of the measured distributions

Proton reconstruction with the TOTEM Roman pot detectors for high-β* LHC data

International audienceThe TOTEM Roman pot detectors are used to reconstruct thetransverse momentum of scattered protons and to estimate thetransverse location of the primary interaction. This paper presentsnew methods of track reconstruction, measurements of strip-leveldetection efficiencies, cross-checks of the LHC beam optics, anddetector alignment techniques, along with their application in theselection of signal collision events. The track reconstruction isperformed by exploiting hit cluster information through a novelmethod using a common polygonal area in the intercept-slopeplane. The technique is applied in the relative alignment ofdetector layers with μm precision. A tag-and-probe method isused to extract strip-level detection efficiencies. The alignment ofthe Roman pot system is performed through time-dependentadjustments, resulting in a position accuracy of 3 μm in thehorizontal and 60 μm in the vertical directions. The goal isto provide an optimal reconstruction tool for central exclusivephysics analyses based on the high-β* data-taking period at√(s) = 13 TeV in 2018