Testing the performance and accuracy of the RELXILL model for the relativistic X-ray reflection from accretion disks

The reflection spectroscopic model RELXILL is commonly implemented in studying relativistic X-ray reflection from accretion disks around black holes. We present a systematic study of the model's capability to constrain the dimensionless spin and ionization parameters from $\sim$6,000 NuSTAR simulations of a bright X-ray source employing the lamppost geometry. We employ high count spectra to show the limitations in the model without being confused with limitations in signal-to-noise. We find that both parameters are well-recovered at 90% confidence with improving constraints at higher reflection fraction, high spin, and low source height. We test spectra across a broad range - first at 10$^6-$10$^7$ and then $\sim$10$^5$ total source counts across the effective 3-79 keV band of NuSTAR, and discover a strong dependence of the results on how fits are performed around the starting parameters, owing to the complexity of the model itself. A blind fit chosen over an approach that carries some estimates of the actual parameter values can lead to significantly worse recovery of model parameters. We further stress on the importance to span the space of nonlinear-behaving parameters like $log~\xi$ carefully and thoroughly for the model to avoid misleading results. In light of selecting fitting procedures, we recall the necessity to pay attention to the choice of data binning and fit statistics used to test the goodness of fit by demonstrating the effect on the photon index $\Gamma$. We re-emphasize and implore the need to account for the detector resolution while binning X-ray data and using Poisson fit statistics instead while analyzing Poissonian data.Comment: 9 pages, 6 figures, accepted for publication in Ap

Twin Deficits in the European Countries

Public debt is a burden on future electors and taxpayers. In absence of constitutional constraints, the incumbent government may shift in the future the cost of some public expenditures or tax reductions, by financing them via new debt. However, according to the Ricardian theorem of public debt, the burden of debt is always anticipated to the present via an increased saving. If this theorem were true, a budget deficit would not affect the current account of the balance of payment. This paper analyzes the re-lationship between trade deficit and budget deficit. Using yearly data for the period between 1970 and 2010 in thirty-three European countries, we find evidence supporting the hypothesis that a chronic and robust budget deficit generates a trade deficit. The dynamic estimates show that a one per cent decrease in the government budget surplus/GDP ratio tends to deteriorate the current account/GDP ratio of 0.37 per cent, confirming previous studies with a different empirical basis. Dividing the sample period in two sub-periods (1970-1991 and 1992-2010), empirical findings show that current and past values of govern-ment budget influence trade balance in the first sub-period, whilst past values of government budget affect trade balance in the most recent years. Moreover, the estimated effect of government budget on current account balance is positive and equal to 0.48 and 0.30, respectively. For the high deficit countries, a long-run relationship between these variables has been found, showing that one percentage point increase in budget surplus/GDP ratio is associated with an improvement in the current account balance of roughly 0.15 percentage point. The estimated long-run government budget elasticity is negative and statistically significant, while the estimated speed of adjustment is equal to 0.33. Finally, Granger causality tests show mixed results

Earnings Manipulation among the Main Industrial Sectors. Evidence from Italy

This paper examines the risk of earnings manipulation among the Stock Italian Companies (“Società per Azioni”) in the main industrial sectors. The companies have been selected from the leading industrial sectors (textile, food, clothing, automotive and metallurgic) which have been generating relevant revenue streams over the past decades. These industry sectors have considered the ones who have driven the Italian Economy. By collecting financial data from AIDA database, we test the existence of Earnings Manipulation within Stock Italian Companies using the Beneish Model (Manipulation Score). The analysis conducted to those companies shows that the application of the model brings to the following interpretation: by using the threshold-limit of -1.78 (Beneish et al., 2013) a half of the companies analyzed has a low probability of manipulating income

Dark Energy and the mass of galaxy clusters

Up to now, Dark Energy evidences are based on the dynamics of the universe on very large scales, above 1 Gpc. Assuming it continues to behave like a cosmological constant $\Lambda$ on much smaller scales, I discuss its effects on the motion of non-relativistic test-particles in a weak gravitational field and I propose a way to detect evidences of $\Lambda \neq 0$ at the scale of about 1 Mpc: the main ingredient is the measurement of galaxy cluster masses.Comment: 5 pages, no figures, references adde

Testing the Kerr nature of black hole candidates using iron line reverberation mapping in the Cardoso-Pani-Rico framework

The iron Kα line commonly observed in the x-ray spectrum of black hole candidates is produced by x-ray fluorescence of the inner accretion disk. This line can potentially be quite a powerful tool to probe the spacetime geometry around these objects and test the Kerr black hole hypothesis. In a previous paper, we studied the ability to constrain possible deviations from the Kerr solution from the standard time-integrated iron line spectrum within the Cardoso-Pani-Rico framework. In the present work, we expand on that study and consider iron line reverberation mapping in the Cardoso-Pani-Rico framework. That is, we consider the time evolution of the iron line profile in response to fluctuations in the x-ray primary source. Our simulations clearly show that the time informatio n in reverberation mapping can better constrain the background metric than the time-integrated approach, and this is true, notably, for the deformation parameter ϵ[subscript 3][superscript r], which is only weakly informed by a time-integrated observation.United States. National Aeronautics and Space Administration (Grant PF5-160144

Modulating mimetic preference with theta burst stimulation of the inferior parietal cortex

We like an object more when we see someone else reaching for it. To what extent is action observation causally linked to object valuation? In this study, we set out to answer to this question by applying continuous theta burst stimulation (cTBS) over the left inferior parietal lobule (IPL). Previous studies pointed to this region as critical in the representation of others' actions and in tool manipulation. However, it is unclear to what extent IPL's involvement simply reflects action observation, rather than a casual role in objects' valuation. To clarify this issue, we measured cTBS-dependent modulations of participants' "mimetic preference ratings", i.e., the difference between the ratings of pairs of familiar objects that were (vs. were not) reached out for by other individuals. Our result shows that cTBS increased mimetic preference ratings for tools, when compared to a control condition without stimulation. This effect was selective for items that were reached for or manipulated by another individual, whilst it was not detected in non-tool objects. Although preliminary, this finding suggests that the automatic and covert simulation of an observed action, even when there is no intention to act on an object, influences explicit affective judgments for objects. This work supports embodied cognition theories by substantiating that our subjective preference is grounded in action