Prospects of long-time-series observations from Dome C for transit search

The detection of transiting extrasolar planets requires high-photometric quality and long-duration photometric stellar time-series. In this paper, we investigate the advantages provided by the Antarctic observing platform Dome C for planet transit detections during its long winter period, which allows for relatively long, uninterrupted time-series. Our calculations include limiting effects due to the Sun and Moon, cloud coverage and the effect of reduced photometric quality for high extinction of target fields. We compare the potential for long time-series from Dome C with a single site in Chile, a three-site low-latitude network as well as combinations of Dome C with Chile and the network, respectively. Dome C is one of the prime astronomical sites on Earth for obtaining uninterrupted long-duration observations in terms of prospects for a high observational duty cycle. The duty cycle of a project can, however, be significantly improved by integrating Dome C into a network of sites.Comment: 10 pages, 9 figures, accepted by PAS

A Multiple Scattering Polarized Radiative Transfer Model: Application to HD 189733b

We present a multiple scattering vector radiative transfer model which produces disk integrated, full phase polarized light curves for reflected light from an exoplanetary atmosphere. We validate our model against results from published analytical and computational models and discuss a small number of cases relevant to the existing and possible near-future observations of the exoplanet HD 189733b. HD 189733b is arguably the most well observed exoplanet to date and the only exoplanet to be observed in polarized light, yet it is debated if the planet's atmosphere is cloudy or clear. We model reflected light from clear atmospheres with Rayleigh scattering, and cloudy or hazy atmospheres with Mie and fractal aggregate particles. We show that clear and cloudy atmospheres have large differences in polarized light as compared to simple flux measurements, though existing observations are insufficient to make this distinction. Futhermore, we show that atmospheres that are spatially inhomogeneous, such as being partially covered by clouds or hazes, exhibit larger contrasts in polarized light when compared to clear atmospheres. This effect can potentially be used to identify patchy clouds in exoplanets. Given a set of full phase polarimetric measurements, this model can constrain the geometric albedo, properties of scattering particles in the atmosphere and the longitude of the ascending node of the orbit. The model is used to interpret new polarimetric observations of HD 189733b in a companion paper.Comment: 13 pages, 13 figures. Accepted for publication in Ap

A Compound model for the origin of Earth's water

One of the most important subjects of debate in the formation of the solar system is the origin of Earth's water. Comets have long been considered as the most likely source of the delivery of water to Earth. However, elemental and isotopic arguments suggest a very small contribution from these objects. Other sources have also been proposed, among which, local adsorption of water vapor onto dust grains in the primordial nebula and delivery through planetesimals and planetary embryos have become more prominent. However, no sole source of water provides a satisfactory explanation for Earth's water as a whole. In view of that, using numerical simulations, we have developed a compound model incorporating both the principal endogenous and exogenous theories, and investigating their implications for terrestrial planet formation and water-delivery. Comets are also considered in the final analysis, as it is likely that at least some of Earth's water has cometary origin. We analyze our results comparing two different water distribution models, and complement our study using D/H ratio, finding possible relative contributions from each source, focusing on planets formed in the habitable zone. We find that the compound model play an important role by showing more advantage in the amount and time of water-delivery in Earth-like planets.Comment: Accepted for publication in The Astrophysical Journa

A Study on Workforce Integration in an International Acquisition

International acquisitions are extremely difficult to maneuver and success is far from guaranteed. Navigating through financial statements is one thing, but trying to link together two or more geographically and culturally diverse workforces is an entirely another thing. This study analyzes fourteen employee interviews from four different companies involved in international acquisitions within the last ten years. It develops a comprehensive comparison of companies looking to partially integrate through hands-off management or fully integrate through synergistic collaboration of workforces. The analysis looks at the actions companies take once the decision is made to grow internationally through mergers and acquisitions in order to form strategic roadmaps at the corporate level and integration roadmaps at the deal-specific level based on whether the companies intend to integrate partially or fully. Of course, different approaches to those actions yield different cultural and operational outcomes, but both convey strong messages that managers should understand when considering an international acquisition

DevOps for Digital Leaders

DevOps; continuous delivery; software lifecycle; concurrent parallel testing; service management; ITIL; GRC; PaaS; containerization; API management; lean principles; technical debt; end-to-end automation; automatio

The Planck-LFI instrument: analysis of the 1/f noise and implications for the scanning strategy

We study the impact of the 1/f noise on the PLANCK Low Frequency Instrument (LFI) osbervations (Mandolesi et al 1998) and describe a simple method for removing striping effects from the maps for a number of different scanning stategies. A configuration with an angle between telescope optical axis and spin-axis just less than 90 degrees (namely 85 degress) shows good destriping efficiency for all receivers in the focal plane, with residual noise degradation < 1-2 %. In this configuration, the full sky coverage can be achieved for each channel separately with a 5 degrees spin-axis precession to maintain a constant solar aspect angle.Comment: submitted to Astronomy and Astrophysics, 12 pages, 15 PostSript figure

Enrichment of the HR 8799 planets by minor bodies and dust

Context. In the Solar System, minor bodies and dust deliver various materials to planetary surfaces. Several exoplanetary systems are known to host inner and outer belts, analogues of the main asteroid belt and the Kuiper belt, respectively. Aims: We study the possibility that exominor bodies and exodust deliver volatiles and refractories to the exoplanets in the well-characterised system HR 8799. Methods: We performed N-body simulations to study the impact rates of minor bodies in the system HR 8799. The model consists of the host star, four giant planets (HR 8799 e, d, c, and b), 650 000 test particles representing the inner belt, and 1 450 000 test particles representing the outer belt. Moreover we modelled dust populations that originate from both belts. Results: Within a million years, the two belts evolve towards the expected dynamical structure (also derived in other works), where mean-motion resonances with the planets carve the analogues of Kirkwood gaps. We find that, after this point, the planets suffer impacts by objects from the inner and outer belt at rates that are essentially constant with time, while dust populations do not contribute significantly to the delivery process. We convert the impact rates to volatile and refractory delivery rates using our best estimates of the total mass contained in the belts and their volatile and refractory content. Over their lifetime, the four giant planets receive between 10-4 and 10-3 M⊕ of material from both belts. Conclusions: The total amount of delivered volatiles and refractories, 5 × 10-3 M⊕, is small compared to the total mass of the planets, 11 × 103 M⊕. However, if the planets were formed to be volatile-rich, their exogenous enrichment in refractory material may well be significant and observable, for example with JWST-MIRI. If terrestrial planets exist within the snow line of the system, volatile delivery would be an important astrobiological mechanism and may be observable as atmospheric trace gases