Time-Resolved Near-Infrared Photometry of Extreme Kuiper Belt Object Haumea

We present time-resolved near-infrared (J and H) photometry of the extreme Kuiper belt object (136108) Haumea (formerly 2003 EL61) taken to further investigate rotational variability of this object. The new data show that the near-infrared peak-to-peak photometric range is similar to the value at visible wavelengths, \Delta m_R = 0.30+/-0.02 mag. Detailed analysis of the new and previous data reveals subtle visible/near-infrared color variations across the surface of Haumea. The color variations are spatially correlated with a previously identified surface region, redder in B-R and darker than the mean surface. Our photometry indicates that the J-H colors of Haumea (J-H=-0.057+/-0.016 mag) and its brightest satellite Hi'iaka (J-H=-0.399+/-0.034 mag) are significantly (>9 sigma) different. The satellite Hi'iaka is unusually blue in J-H, consistent with strong 1.5 micron water-ice absorption. The phase coefficient of Haumea in the J-band is found to increase monotonically with wavelength in the range 0.4<lambda<1.3. We compare our findings with other Solar system objects and discuss implications regarding the surface of Haumea.Comment: 10 pages, 10 figures, 6 tables. Accepted for publication in The Astronomical Journal (2008 November 28

Credit Risk and Capital Requirements for the Portuguese Banking System

In this study, an assessment of the impact of Basel II capital requirement rules driven by credit risk of non-financial firms is performed. Intervals of variation for the risk drivers are established such that capital requirements for firms' credit risk under Basel II exceed capital requirements under Basel I. Moreover, a characterization of the Portuguese Banking system, which includes a description of corporate credit and its associated probabilities of default, and the computation of capital requirements are performed.

The Sizes of Kuiper Belt Objects

One of the most fundamental problems in the study of Kuiper belt objects (KBOs) is to know their true physical size. Without knowledge of their albedos we are not able to distinguish large and dark from small and bright KBOs. Spitzer produced rough estimates of the sizes and albedos of about 20 KBOs, and the Herschel space telescope will improve on those initial measurements by extending the sample to the ~150 brightest KBOs. SPICA's higher sensitivity instruments should allow us not only to broaden the sample to smaller KBOs but also to achieve a statistically significant sample of KBO thermal light curves (Herschel will measure only six objects). A large sample covering a broad range of sizes will be key to identify meaningful correlations between size and other physical and surface properties that constrain the processes of formation and evolution of the solar system.Comment: 6 pages, 6 figures, Proc. Workshop "The Space Infrared Telescope for Cosmology and Astrophysics: Revealing the Origins of Planets and Galaxies

Analysis of the Predictors of Default for Portuguese Firms

The paper presents an insolvency risk analysis of Portuguese companies with three techniques: logistic regression, discriminant analysis and support vector machines (SVM). It identifies the most critical predictors of default based on the accounting, employee and debt concentration data. A comparison of the three methods reveals a superiority of SVM. Non-financial information such as employee data and the debt concentration index appear to be strong predictors of default.

A Change in the Lightcurve of Kuiper Belt Contact Binary (139775) 2001 QG298

New observations show that the lightcurve of Kuiper belt contact binary (139775) 2001 QG298 has changed substantially since the first observations in 2003. The 2010 lightcurve has a peak-to-peak photometric of range \Deltam{2010}=0.7\pm0.1 mag, significantly lower than in 2003, \Deltam{2003}=1.14\pm0.04 mag. This change is most simply interpreted if 2001 QG298 has an obliquity near 90 deg. The observed decrease in \Deltam is caused by a change in viewing geometry, from equator-on in 2003 to nearly 16 deg (the orbital angular distance covered by the object between the observations) off the equator in 2010. The 2003 and 2010 lightcurves have the same rotation period and appear in phase when shifted by an integer number of full rotations, also consistent with high obliquity. Based on the new 2010 lightcurve data, we find that 2001 QG298 has an obliquity {\epsilon}=90\pm30 deg. Current estimates of the intrinsic fraction of contact binaries in the Kuiper belt are debiased assuming that these objects have randomly oriented spins. If, as 2001 QG298, KBO contact binaries tend to have large obliquities, a larger correction is required. As a result, the abundance of contact binaries may be larger than previously believed.Comment: 28 pages, 10 figures, 5 tables. Accepted for publication in The Astronomical Journal (2011 July 18

Heidegger, technology and sustainability: between intentionality, accountability and empowerment

Transition is the adequate term for characterising contemporary societies. Norms and values are in transit, led by a technological revolution, which is, in itself, the tip of the iceberg of millenary social and cultural changes. Heidegger, one of the leading philosophers of the twentieth century, captured this tension between social change and innovative technology and showed that the Western civilisation was captive of ontological instances whose role was already pin-pointed by Greek Antiquity philosophy but which went underground with Modernity. The product of Heidegger’s work was a revolution in Western thought, which found echoes across all areas of society. Taking Husserl’s call for “back to the things themselves”, Heidegger’s impact has empowered the calls for more sustainable and resilient societies. Sustainability models, with its three pillars of environmental, economic and social sustainability, are directly dependent upon the role of technology and of information science in shaping current patterns of production and consumption in contemporary societies. Industrial, academic and political discourses already voice such taken for granted assumptions. Nevertheless, it is crucial to clarify and to highlight the links between economic evolution and progress, social change and the catalysing role of technology, taken as an enabler of human action.info:eu-repo/semantics/publishedVersio

Outer solar system possibly shaped by a stellar fly-by

The planets of our solar system formed from a gas-dust disk. However, there are some properties of the solar system that are peculiar in this context. First, the cumulative mass of all objects beyond Neptune (TNOs) is only a fraction of what one would expect. Second, unlike the planets themselves, the TNOs do not orbit on coplanar, circular orbits around the Sun, but move mostly on inclined, eccentric orbits and are distributed in a complex way. This implies that some process restructured the outer solar system after its formation. However, some of TNOs, referred to as Sednoids, move outside the zone of influence of the planets. Thus external forces must have played an important part in the restructuring of the outer solar system. The study presented here shows that a close fly-by of a neighbouring star can simultaneously lead to the observed lower mass density outside 30 AU and excite the TNOs onto eccentric, inclined orbits, including the family of Sednoids. In the past it was estimated that such close fly-bys are rare during the relevant development stage. However, our numerical simulations show that such a scenario is much more likely than previously anticipated. A fly-by also naturally explains the puzzling fact that Neptune has a higher mass than Uranus. Our simulations suggest that many additional Sednoids at high inclinations still await discovery, perhaps including bodies like the postulated planet X.Comment: 16 pages, 7 figures, accepted by Ap