The Spectral Evolution of Transient Anomalous X-ray Pulsar XTE J1810--197

(Abridged) We present a multi-epoch spectral study of the Transient Anomalous X-ray Pulsar XTE J1810-197 obtained with the XMM X-ray telescope. Four observations taken over the course of a year reveal strong spectral evolution as the source fades from outburst. The origin of this is traced to the individual decay rates of the pulsar's spectral components. A 2-T fit at each epoch requires nearly constant temperatures of kT=0.25 & 0.67 keV while the component luminosities decrease exponentially with tau=900 & 300d, respectively. One possible interpretation is that the slowly decaying cooler component is the radiation from a deep heating event that affected a large fraction of the crust, while the hotter component is powered by external surface heating at the foot-points of twisted magnetic field lines, by magnetospheric currents that are decaying more rapidly. The energy-dependent pulse profile of XTE J1810-197 is well modeled at all epochs by the sum of a sine and triangle function. These profiles peak at the same phase, suggesting a concentric surface emission geometry. The spectral and pulse evolution together argue against the presence of a significant ``power-law'' contribution to the X-ray spectrum below 8 keV. The extrapolated flux is projected to return to the historic quiescent level, characterized by an even cooler blackbody spectrum, by the year 2007.Comment: 12 pages, 6 Figures, Latex, emulateapj. To appear in the Astrophysical Journa

Presidential Address: A View From the Lectern

This paper explores the relationship among teaching, research, and publications for, the author argues, a good teacher must carry out advanced historical research and >report results to a wider academic audience. This observation leads to an examination of three kinds of questions which challenge the historian as teacher: the first, questions to which the primary and secondary literature provide no answer; the second, questions to which standard works offer no adequate response but which inspire research and rethinking and thereby lead to a new understanding of the issue; and the third, questions which can be fully answered only by informed speculation. The paper then illustrates the challenge posed by each type of question by looking at important incidents in twentieth-century Canadian history: the first, why Prime Minister Borden on 1 January 1916 doubled Canada's manpower in the Great War to five hundred thousand; the second, why did the tariff disappear as an issue from elections after 1935; and the third, why did the Cabinet accept the forced resignation of J. L. Ralston as Minister of National Defence in November of 1944? The specialised knowledge required to respond to such questions necessarily enriches our overall understanding of the past.Cet article explore Ia relation entre l'enseignement, la recherche et les publications, car l'auteur croit qu'un bon universitaire doit à la fois effectuer des travaux de recherches avancées et en communiquer les résultats à un auditoire plus large. Cette prémisse renvoie à trois types de questions auxquelles les enseignants font face. Il s'agit premièrement des questions auxquelles les sources primaires et la littérature ne donnent aucune réponse. En second lieu, des questions auxquelles les travaux habituels ne donnent pas de réponse satisfaisante, mais qui provoquent la recherche et la réflexion en vue de proposer des solutions. Et troisièmement, des questions auxquelles l'on ne peut répondre que par des spéculations fondées sur de solides connaissances. En guise d'illustrations des défis posés par chaque ordre de questions, l'auteur considère trois problèmes majeurs de l'histoire canadienne. D'abord, comment expliquer la décision du Premier ministre Borden, le premier janvier 1916, de doubler la participation des soldats canadiens à la Grande guerre, pour atteindre le nombre de 500 000 soldats ? Ensuite, pourquoi les tarifs douaniers ont-ils disparu des enjeux électoraux après 1935 ? Enfin, pourquoi le cabinet libéral a-t-il accepté la démission du ministre de la Défense nationale, J. L. Ralston, en novembre 1944 ? Les connaissances spécialisées auxquelles un professeur devra avoir recours pour répondre à ces questions enrichiront sans aucun doute sa compréhension du passé

Effectiveness evaluation of STOL transport operations

A short-takeoff and landing (STOL) systems simulation model has been developed and implemented in a computer code (known as STOL OPS) which permits evaluation of the operation of a STOL aircraft and its avionics in a commercial airline operating environment. STOL OPS concentrated on the avionics functions of navigation, guidance, control, communication, hazard aviodance, and systems management. External world factors influencing the operation of the STOL aircraft include each airport and its geometry, air traffic at each airport, air traffic control equipment and procedures, weather (including winds and visibility), and the flight path between each airport served by the route. The development of the STOL OPS program provides NASA a set of computer programs which can be used for detailed analysis of a STOL aircraft and its avionics and permit establishment of system requirements as a function of airline mission performance goals

Fading of the Transient Anomalous X-ray Pulsar XTE J1810-197

Three observations of the 5.54 s Transient Anomalous X-ray Pulsar XTE J1810-197 obtained over 6 months with the Newton X-Ray Multi-Mirror Mission (XMM-Newton) are used to study its spectrum and pulsed light curve as the source fades from outburst. The decay is consistent with an exponential of time constant 300 days, but not a power law as predicted in some models of sudden deep crustal heating events. All spectra are well fitted by a blackbody plus a steep power law, a problematic model that is commonly fitted to anomalous X-ray pulsars (AXPs). A two-temperature blackbody fit is also acceptable, and better motivated physically in view of the faint optical/IR fluxes, the X-ray pulse shapes that weakly depend on energy in XTE J1810-197, and the inferred emitting areas that are less than or equal to the surface area of a neutron star. The fitted temperatures remained the same while the flux declined by 46%, which can be interpreted as a decrease in area of the emitting regions. The pulsar continues to spin down, albeit at a reduced rate of (5.1+/-1.6)x10^{-12} s s^{-1}. The inferred characteristic age Tau_c = P/2Pdot ~17,000 yr, magnetic field strength B_s ~1.7x10^{14} G, and outburst properties are consistent with both the outburst and quiescent X-ray luminosities being powered by magnetic field decay, i.e., XTE J1810-197 is a magnetar.Comment: 10 pages, 5 figures, accepted by Ap.

The Lightest Pseudo-Goldstone Boson at Future e+e- Colliders

In a class of models of dynamical symmetry breaking not ruled out by the available data, the lightest neutral pseudo-Nambu-Goldstone boson P0 contains only down-type techniquarks and charged technileptons. Its mass scale is naturally determined by the b-quark and therefore it is likely to be light. As the presence of pseudo-Nambu-Goldstone bosons in models of dynamical symmetry breaking is a quite general feature, the search of the P0 at colliders is an interesting opportunity of putting limits on or discovering a dynamical electroweak symmetry breaking scenario. In this note we discuss the prospects for discovering and studying the P0 at future e+e- and gamma-gamma colliders.Comment: 15 pages, 8 figures, LaTeX (epsfig), Proceedings of the Second ECFA/DESY Study on Physics Studies for a Future Linear Collide

SAX J1808.4-3658, an accreting millisecond pulsar shining in gamma rays?

We report the detection of a possible gamma-ray counterpart of the accreting millisecond pulsar SAX J1808.4-3658. The analysis of ~6 years of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi-LAT) within a region of 15deg radius around the position of the pulsar reveals a point gamma-ray source detected at a significance of ~6 sigma (Test Statistic TS = 32), with position compatible with that of SAX J1808.4-3658 within 95% Confidence Level. The energy flux in the energy range between 0.6 GeV and 10 GeV amounts to (2.1 +- 0.5) x 10-12 erg cm-2 s-1 and the spectrum is well-represented by a power-law function with photon index 2.1 +- 0.1. We searched for significant variation of the flux at the spin frequency of the pulsar and for orbital modulation, taking into account the trials due to the uncertainties in the position, the orbital motion of the pulsar and the intrinsic evolution of the pulsar spin. No significant deviation from a constant flux at any time scale was found, preventing a firm identification via time variability. Nonetheless, the association of the LAT source as the gamma-ray counterpart of SAX J1808.4-3658 would match the emission expected from the millisecond pulsar, if it switches on as a rotation-powered source during X-ray quiescence.Comment: 8 pages, 4 figures, accepted by MNRA

Loci de rasgos binarios que influyen en la expresión del comportamiento higiénico de las abejas melíferas

This study was conducted to detect binary trait loci (BTLs) that influence the expression of hygienic behavior of individual honey bee workers and to locate genetic markers that are associated to these BTLs on a genetic map derived from bees that perform hygienic behavior of a backcross colony. Samples of workers that perform hygienic behavior and workers that not perform hygienic behavior that were used as controls were collected from the colony.Este estudio se realizó, para detectar loci de rasgos binarios (BTL) que influyen en la expresión del comportamiento higiénico de abejas obreras y para localizar marcadores genéticos asociados a estos BTL en un mapa de ligamiento. Se recolectaron abejas que realizaron el comportamiento higiénico y abejas que no realizaron el comportamiento higiénico de una colonia producto de una retrocruza. Se construyó, un mapa genético utilizando marcadores AFLP generados a partir del ADN de las abejas que realizaron el comportamiento higiénico

Development of an evaluation technique for interplanetary mission astrionics Interim scientific report

Evaluating astrionics for interplanetary flyby missions using penalty function