Synergistic angular and spectral estimation of aerosol properties using CHRIS/PROBA-1 and simulated Sentinel-3~data

A method has been developed to estimate Aerosol Optical Depth (AOD), Fine Mode Fraction (FMF) and Single Scattering Albedo (SSA) over land surfaces using simulated Sentinel-3 data. The method uses inversion of a coupled surface/atmosphere radiative transfer model, and includes a general physical model of angular surface reflectance. An iterative process is used to determine the optimum value of the aerosol properties providing the best fit of the corrected reflectance values for a number of view angles and wavelengths with those provided by the physical model. A method of estimating AOD using only angular retrieval has previously been demonstrated on data from the ENVISAT and PROBA-1 satellite instruments, and is extended here to the synergistic spectral and angular sampling of Sentinel-3 and the additional aerosol properties. The method is tested using hyperspectral, multi-angle Compact High Resolution Imaging Spectrometer (CHRIS) images. The values obtained from these CHRIS observations are validated using ground based sun-photometer measurements. Results from 22 image sets using the synergistic retrieval and improved aerosol models show an RMSE of 0.06 in AOD, reduced to 0.03 over vegetated targets

Particulate emissions from large North American wildfires estimated using a new top-down method

Particulate matter emissions from wildfires affect climate, weather and air quality. However, existing global and regional aerosol emission estimates differ by a factor of up to 4 between different methods. Using a novel approach, we estimate daily total particulate matter (TPM) emissions from large wildfires in North American boreal and temperate regions. Moderate Resolution Imaging Spectroradiometer (MODIS) fire location and aerosol optical thickness (AOT) data sets are coupled with HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) atmospheric dispersion simulations, attributing identified smoke plumes to sources. Unlike previous approaches, the method (i) combines information from both satellite and AERONET (AErosol RObotic NETwork) observations to take into account aerosol water uptake and plume specific mass extinction efficiency when converting smoke AOT to TPM, and (ii) does not depend on instantaneous emission rates observed during individual satellite overpasses, which do not sample night-time emissions. The method also allows multiple independent estimates for the same emission period from imagery taken on consecutive days. <br><br> Repeated fire-emitted AOT estimates for the same emission period over 2 to 3 days of plume evolution show increases in plume optical thickness by approximately 10 % for boreal events and by 40 % for temperate emissions. Inferred median water volume fractions for aged boreal and temperate smoke observations are 0.15 and 0.47 respectively, indicating that the increased AOT is partly explained by aerosol water uptake. TPM emission estimates for boreal events, which predominantly burn during daytime, agree closely with bottom-up Global Fire Emission Database (GFEDv4) and Global Fire Assimilation System (GFASv1.0) inventories, but are lower by approximately 30 % compared to Quick Fire Emission Dataset (QFEDv2) PM_2. 5, and are higher by approximately a factor of 2 compared to Fire Energetics and Emissions Research (FEERv1) TPM estimates. The discrepancies are larger for temperate fires, which are characterized by lower median fire radiative power values and more significant night-time combustion. The TPM estimates for this study for the biome are lower than QFED PM_2. 5 by 35 %, and are larger by factors of 2.4, 3.2 and 4 compared with FEER, GFED and GFAS inventories respectively. A large underestimation of TPM emission by bottom-up GFED and GFAS indicates low biases in emission factors or consumed biomass estimates for temperate fires

Classical tests of general relativity in the Newtonian limit of Schwarzschild-de Sitter spacetime

Recently it has been shown that despite previous claims the cosmological constant affects light bending. In the present article we study light bending and the advance of Mercury's perihelion in the context of the Newtonian limit of Schwarzschild-de Sitter spacetime employing the special relativistic equivalence of mass and energy. In both cases, up to a constant factor, we find the same results as in the full general relativistic treatment of the same phenomena. These approximate and intuitive arguments demonstrate clearly what effects should have been expected from the presence of $\Lambda$ in the general relativistic treatment of these phenomena.Comment: 12 pages, Revtex, 1 figur

Z2SAL: a translation-based model checker for Z

Despite being widely known and accepted in industry, the Z formal specification language has not so far been well supported by automated verification tools, mostly because of the challenges in handling the abstraction of the language. In this paper we discuss a novel approach to building a model-checker for Z, which involves implementing a translation from Z into SAL, the input language for the Symbolic Analysis Laboratory, a toolset which includes a number of model-checkers and a simulator. The Z2SAL translation deals with a number of important issues, including: mapping unbounded, abstract specifications into bounded, finite models amenable to a BDD-based symbolic checker; converting a non-constructive and piecemeal style of functional specification into a deterministic, automaton-based style of specification; and supporting the rich set-based vocabulary of the Z mathematical toolkit. This paper discusses progress made towards implementing as complete and faithful a translation as possible, while highlighting certain assumptions, respecting certain limitations and making use of available optimisations. The translation is illustrated throughout with examples; and a complete working example is presented, together with performance data

Testing asteroseismology with Gaia DR2: Hierarchical models of the Red Clump

Asteroseismology provides fundamental stellar parameters independent of distance, but subject to systematics under calibration. Gaia DR2 has provided parallaxes for a billion stars, which are offset by a parallax zero-point. Red Clump (RC) stars have a narrow spread in luminosity, thus functioning as standard candles to calibrate these systematics. This work measures how the magnitude and spread of the RC in the Kepler field are affected by changes to temperature and scaling relations for seismology, and changes to the parallax zero-point for Gaia. We use a sample of 5576 RC stars classified through asteroseismology. We apply hierarchical Bayesian latent variable models, finding the population level properties of the RC with seismology, and use those as priors on Gaia parallaxes to find the parallax zero-point offset. We then find the position of the RC using published values for the zero-point. We find a seismic temperature insensitive spread of the RC of ~0.03 mag in the 2MASS K band and a larger and slightly temperature-dependent spread of ~0.13 mag in the Gaia G band. This intrinsic dispersion in the K band provides a distance precision of ~1% for RC stars. Using Gaia data alone, we find a mean zero-point of -41 $\pm$ 10 $\mu$as. This offset yields RC absolute magnitudes of -1.634 $\pm$ 0.018 in K and 0.546 $\pm$ 0.016 in G. Obtaining these same values through seismology would require a global temperature shift of ~-70 K, which is compatible with known systematics in spectroscopy.Comment: Accepted for publication in MNRA

Barium & related stars and their white-dwarf companions II. Main-sequence and subgiant stars

Barium (Ba) dwarfs and CH subgiants are the less-evolved analogues of Ba and CH giants. They are F- to G-type main-sequence stars polluted with heavy elements by a binary companion when the latter was on the Asymptotic Giant Branch (AGB). This companion is now a white dwarf that in most cases cannot be directly detected. We present a large systematic study of 60 objects classified as Ba dwarfs or CH subgiants. Combining radial-velocity measurements from HERMES and SALT high-resolution spectra with radial-velocity data from CORAVEL and CORALIE, we determine the orbital parameters of 27 systems. We also derive their masses by comparing their location in the Hertzsprung-Russell diagram with evolutionary models. We confirm that Ba dwarfs and CH subgiants are not at different evolutionary stages and have similar metallicities, despite their different names. Additionally, Ba giants appear significantly more massive than their main-sequence analogues. This is likely due to observational biases against the detection of hotter main-sequence post-mass-transfer objects. Combining our spectroscopic orbits with the Hipparcos astrometric data, we derive the orbital inclinations and the mass of the WD companion for four systems. Since this cannot be done for all systems in our sample yet (but should be with upcoming Gaia data releases), we also analyse the mass-function distribution of our binaries. We can model this distribution with very narrow mass distributions for the two components and random orbital orientation on the sky. Finally, based on BINSTAR evolutionary models, we suggest that the orbital evolution of low-mass Ba systems can be affected by a second phase of interaction along the Red Giant Branch of the Ba star, impacting on the eccentricities and periods of the giants.Comment: Accepted for publication in A&A on the 5th of April, 201

Defining forgiveness: Christian clergy and general population perspectives.

The lack of any consensual definition of forgiveness is a serious weakness in the research literature (McCullough, Pargament &amp; Thoresen, 2000). As forgiveness is at the core of Christianity, this study returns to the Christian source of the concept to explore the meaning of forgiveness for practicing Christian clergy. Comparisons are made with a general population sample and social science definitions of forgiveness to ensure that a shared meaning of forgiveness is articulated. Anglican and Roman Catholic clergy (N = 209) and a general population sample (N = 159) completed a postal questionnaire about forgiveness. There is agreement on the existence of individual differences in forgiveness. Clergy and the general population perceive reconciliation as necessary for forgiveness while there is no consensus within psychology. The clergy suggests that forgiveness is limitless and that repentance is unnecessary while the general population suggests that there are limits and that repentance is necessary. Psychological definitions do not conceptualize repentance as necessary for forgiveness and the question of limits has not been addressed although within therapy the implicit assumption is that forgiveness is limitless.</p

Identifying the mechanisms underpinning recognition of structured sequences of action

© 2012 The Experimental Psychology SocietyWe present three experiments to identify the specific information sources that skilled participants use to make recognition judgements when presented with dynamic, structured stimuli. A group of less skilled participants acted as controls. In all experiments, participants were presented with filmed stimuli containing structured action sequences. In a subsequent recognition phase, participants were presented with new and previously seen stimuli and were required to make judgements as to whether or not each sequence had been presented earlier (or were edited versions of earlier sequences). In Experiment 1, skilled participants demonstrated superior sensitivity in recognition when viewing dynamic clips compared with static images and clips where the frames were presented in a nonsequential, randomized manner, implicating the importance of motion information when identifying familiar or unfamiliar sequences. In Experiment 2, we presented normal and mirror-reversed sequences in order to distort access to absolute motion information. Skilled participants demonstrated superior recognition sensitivity, but no significant differences were observed across viewing conditions, leading to the suggestion that skilled participants are more likely to extract relative rather than absolute motion when making such judgements. In Experiment 3, we manipulated relative motion information by occluding several display features for the duration of each film sequence. A significant decrement in performance was reported when centrally located features were occluded compared to those located in more peripheral positions. Findings indicate that skilled participants are particularly sensitive to relative motion information when attempting to identify familiarity in dynamic, visual displays involving interaction between numerous features

KOI-3890: A high mass-ratio asteroseismic red-giant++M-dwarf eclipsing binary undergoing heartbeat tidal interactions

KOI-3890 is a highly eccentric, 153-day period eclipsing, single-lined spectroscopic binary system containing a red-giant star showing solar-like oscillations alongside tidal interactions. The combination of transit photometry, radial velocity observations, and asteroseismology have enabled the detailed characterisation of both the red-giant primary and the M-dwarf companion, along with the tidal interaction and the geometry of the system. The stellar parameters of the red-giant primary are determined through the use of asteroseismology and grid-based modelling to give a mass and radius of $M_{\star}=1.04\pm0.06\;\textrm{M}_{\odot}$ and $R_{\star}=5.8\pm0.2\;\textrm{R}_{\odot}$ respectively. When combined with transit photometry the M-dwarf companion is found to have a mass and radius of $M_{\mathrm{c}}=0.23\pm0.01\;\textrm{M}_{\odot}$ and $R_{\mathrm{c}}=0.256\pm0.007\;\textrm{R}_{\odot}$. Moreover, through asteroseismology we constrain the age of the system through the red-giant primary to be $9.1^{+2.4}_{-1.7}\;\mathrm{Gyr}$. This provides a constraint on the age of the M-dwarf secondary, which is difficult to do for other M-dwarf binary systems. In addition, the asteroseismic analysis yields an estimate of the inclination angle of the rotation axis of the red-giant star of $i=87.6^{+2.4}_{-1.2}$ degrees. The obliquity of the system\textemdash the angle between the stellar rotation axis and the angle normal to the orbital plane\textemdash is also derived to give $\psi=4.2^{+2.1}_{-4.2}$ degrees showing that the system is consistent with alignment. We observe no radius inflation in the M-dwarf companion when compared to current low-mass stellar models.Comment: 11 pages, 5 figures, accepted for publication in MNRA