Spectral analysis of a large sample of BeppoSAX Seyfert spectra with Comptonization models: Preliminary results

We present preliminary results of the spectral analysis of a large sample of Seyfert galaxies observed by BeppoSAX. The only selection criterium was a sufficiently large S/N ratio (>10) in the PDS band (12-200 keV) to allow good detection up to the highest energy. The resulting sample is composed of 28 objects (17 Seyfert 1, 11 Seyfert 2) and 50 observations. Our main effort here is to adopt Comptonization models to fit the different spectra on a truly broad band basis (0.1-200 keV). We use two distinct disc-corona configurations, an anisotropic slab and an isotropic spherical one. We discuss the distributions of the physical parameters, like temperature and optical depth of the corona and the reflection component, among this sample. We also discussed the existence (or inexistence) of correlations between these parameters.Comment: 4 pages, 2 figures. Proc. of the meeting: "The Restless High-Energy Universe" (Amsterdam, The Netherlands), E.P.J. van den Heuvel, J.J.M. in 't Zand, and R.A.M.J. Wijers Ed

Models of Comptonization

After a rapid introduction about the models of comptonization, we present some simulations that underlines the expected capabilities of Simbol-X to constrain the presence of this process in objects like AGNs or XRB.Comment: 5 pages, 6 figures, invited talk at 'Simbol-X: the hard X-ray universe in focus', Bologna (Italy), 14-16 May, 2007. To appear in Memorie della SAI

Devaluation (levels versus rates) and balance of payments in a cash-in-advance economy

This paper investigates the consequences of the currency devalution, both in levels and rates, on the balance of payments in a cash-in-advance economy with finite horizons, endogenous capital accumulation and international capital immobility. In this context, a once and for all currency devaluation induces a balance of payments surplus, whereas a sustained increase in the rate of devaluation produces, in principle, an ambiguous effect on the balance of payments. If however non-restrictive assumptions on some structural parameters are made, an increase in the devaluation rate leads to a balance of payments surplus, the exact opposite of Calvo's result (1981).Devaluation; Balance of payments; Cash-in-advance constraint; Overlapping generations.

Taxing Land Rent in an Open Economy

This paper analyzes the effects of a land rent tax on capital formation and foreign investment in a life-cycle small open economy with endogenous labor-leisure choices. Differently from the previous literature, the consequences of land taxation critically depend on how the tax proceeds are used by the government. A land tax depresses capital formation, crowds out foreign investment and pulls up national wealth and consumption when consumers are lump-sum compensated for the tax. If the proceeds from taxation were used for financing un-productive government expenditure, land taxation would be neutral in its effects on capital stock, nonhuman wealth and labor. When the tax proceeds are used to reduce labor taxes, the land tax exerts ambiguous effects on capital stock and manhours, and spurs nonhuman wealth accumulation.Land Taxation, Labor Supply, Capital Accumulation, Overlapping-generations

Optimal Taxation of Capital Income in Models with Endogenous Fertility

This paper studies the issue of the efficient taxation of capital income in intertemporal optimizing models with infinite horizons and endogenous population growth. We discover that, in the steady state, the optimal capital income tax is negative when the economy is closed. Instead, in a small open economy facing perfect capital mobility, the Chamley-Judd result of a zero tax rate is obtained if capital taxation is source-based; otherwise, income from wealth should be subsidized if taxation is residence-based. Moreover, we find that in our setup, taxing capital income with immediate expensing of capital expenditure may replicate the first-best equilibrium when labor is subsidized. Our findings, which depart substantially from those obtained in representative agent models with an endogenous labor supply, are to be ascribed to a wealth effect in the fertility choices that directly affects the pseudo-welfare function of the social planner.Factor Income Taxes; Second-best Analysis; Endogenous Population Growth; Capital Formation

Second-Best Optimal Taxation of Oil and Capital in a Small Open Economy

This paper analyzes the efficient taxation of oil and capital income in an oil-dependent infinite-lived economy facing perfect capital mobility. Two cases are examined: one with product market imperfections and free tax choice, one with perfect competition and tax restrictions. The optimal tax rates on oil and capital strictly depend on the international tax system implemented; however, they are also affected by the degree of market power and the extent to which monopoly profits are taxed, the type of tax restrictions and the use of oil (as an input or a consumer good). Under the residence-based system, capital income should always be exempted from taxation, while the optimal tax on productive oil may differ from zero. Under the source-based system, second-best taxes on capital and oil are non-zero.Optimal Factor Taxation, Oil, Capital Income, Residence-based System, Source-Based System

Money, labour supply, and growth in a liquidity costs economy

Economists often compare two ways of work sharing : increase of part-time work and the reduction of the weekly work time. Most of the literature focuses upon the labour demand size. The aim of this paper is to tackle this question from the point of view of labour supply. We calibrate on French data a sequential job search model, which as two specific features : the characterization of job offers in terms of utility level which combines hourly wage rates with available leisure time and the fact that unemployment is not the only compatible state with a job search. Simulations of the model show that, for a given labour demand, the probability to be unemployed increases with the proportion of part-time jobs and decrease with the reduction of the weekly work time.

Money, Endogenous Fertility and Economic Growth

This paper analyses the issue of money superneutrality through an intertemporal optimising model of capital accumulation and inflation with endogenous fertility, i.e. endogenous population growth. The model establishes an inverse relation between capital-labour ratio and population growth, which represents the crucial element for having non-superneutrality of money. A higher monetary growth rate increases fertility, since it reduces its opportunity cost, and hence diminishes capital intensity, per capita output and consumption. The reverse Tobin effect on capital-labour ratio and per capita output is matched by an increase in aggregate capital and output growth rates. In this framework, the optimal monetary growth rule, which is a distorted Friedman rule, can call for either a contraction or an expansion of the money supply.Money Superneutrality, Fertility, Capital Accumulation

Wealth Accumulation and Growth in a Specific-Factors Model of Trade and Finance.

This paper investigates the allocative properties of an OLG specificfactors small open economy facing perfect capital mobility. Wealth formation, economic development and different labor market regimes are at the center-stage of the analysis. In a model with competitive wages and no unemployment, we find that exogenous shocks that do not affect human wealth —like the terms of trade and land endowment shifts— or the propensity to save, leave nonhuman wealth, consumption and aggregate labor unchanged; in such cases, capital formation is driven by the static effects exerted on sectoral labor. Disturbances that alter human wealth —like the world interest rate, and capital and labor taxation shocks— or the thrift rate, instead, affect nonhuman wealth and consumption as they involve an intergenerational redistribution of resources that modifies aggregate saving; labor hours supplied may be changed. In these circumstances, capital accumulation is the result of the consequences exerted on financial wealth and input demands. The consideration of a labor market with structural unemployment does not qualitatively affect the results, except for the world interest rate and the rate of time discount shifts. Our results differ substantially from those obtained in static and dynamic specific-factors setups with financial autharky.Specific-Factors; Capital Accumulation; Land; Net Foreign Assets; Finite Horizons.