Chandra and RXTE studies of the X-ray/gamma-ray millisecond pulsar PSR J0218+4232

We report on high-resolution spatial and timing observations of the millisecond pulsar PSR J0218+4232 performed with the Chandra X-ray Observatory (CXO) and the Rossi X-ray Timing Explorer (RXTE). With these observations we were able to study a) the possible spatial extent at X-ray energies of the DC source coincident with PSR J0218+4232 in detail (CXO), b) the relative phasing between the X-ray, radio and gamma-ray profiles (CXO and RXTE) and c) the spectral properties at energies beyond 10 keV (RXTE). We found no indications for extended emission at X-ray energies down to ~ 1 arcsec scales and confirmed the presence of a point-like DC-component. The 2 non-thermal pulses in the X-ray profile are found to be aligned with 2 of the 3 pulses visible at radio-frequencies and more importantly with the two gamma-ray pulses seen in the EGRET 100-1000 MeV pulse profile. The latter reduces now the random occurrence probability for the detected gamma-ray signal to ~ 1.E-6, which corresponds to a 4.9 sigma detection significance.Comment: 8 pages,7 figures, accepted for publication in Adv Sp Res: Proceedings of the 34th COSPAR Scientific Assembly held in Housto

A Policy Theory Evaluation of the Dutch SME and Entrepreneurship Policy Program between 1982 and 2003

The present paper reconstructs and analyses the assumptions – i.e. the policy theory – underlying the development of the SME and Entrepreneurship Policy Program in general and the Establishment Act and the Loan Guarantee (BBMKB) in particular between 1982-2003. The analysis links these assumptions to policy output results and policy effects. We find that the foundation of the policy theories of the Establishment Act and the Loan Guarantee requires improvement with respect to implicit assumptions and lacking warrants. We also find that the implied policy effects cohere with formal policy objectives.

The role of accretion disks in the formation of massive stars

We present radiation hydrodynamics simulations of the collapse of massive pre-stellar cores. We treat frequency dependent radiative feedback from stellar evolution and accretion luminosity at a numerical resolution down to 1.27 AU. In the 2D approximation of axially symmetric simulations, it is possible for the first time to simulate the whole accretion phase of several 10^5 yr for the forming massive star and to perform a comprehensive scan of the parameter space. Our simulation series show evidently the necessity to incorporate the dust sublimation front to preserve the high shielding property of massive accretion disks. Our disk accretion models show a persistent high anisotropy of the corresponding thermal radiation field, yielding to the growth of the highest-mass stars ever formed in multi-dimensional radiation hydrodynamics simulations. Non-axially symmetric effects are not necessary to sustain accretion. The radiation pressure launches a stable bipolar outflow, which grows in angle with time as presumed from observations. For an initial mass of the pre-stellar host core of 60, 120, 240, and 480 Msol the masses of the final stars formed in our simulations add up to 28.2, 56.5, 92.6, and at least 137.2 Msol respectively.Comment: 4 pages, 2 figures, Computational Star Formation Proceedings IAU Symposium No. 270, 2010, Ed.: J. Alves, B. Elmegreen, J. Girart & V. Trimbl

ENDOGENOUS TRANSACTION COSTS AND TRADABILITY IN A MICRO ECONOMYWIDE MODEL - A STYLIZED APPLICATION WITH NONSEPARABLE HOUSEHOLDS

This paper analyzes effects of transaction costs on household responses, adding to direct effects via price-bands, indirect effects through reduced availability of productive resources and through changes in price formation. A micro economywide model with nonseparable household models is developed, in which transaction costs determine effective prices through an endogenous, household-specific price-band. Moreover, transaction costs influence household decisions by claiming productive resources, and by affecting endogenous prices at household or micro-economy level. Comparison of two stylized village model specifications indicates that indirect effects of transaction costs reduce household supply response, despite reducing the range of prices for which households operate within their price-band. Results show that transaction costs need to be identified in terms of commodities used for transactions, and in terms of tradability of these commodities, to account for indirect effects of transaction costs.Research Methods/ Statistical Methods,