39 research outputs found
Unraveling the high-energy emission components of gamma-ray binaries
The high and very-high energy spectrum of gamma-ray binaries has become a
challenge for all theoretical explanations since the detection of powerful,
persistent GeV emission from LS 5039 and LS I +61 303 by Fermi/LAT. The
spectral cutoff at a few GeV indicates that the GeV component and the fainter,
hard TeV emission above 100 GeV are not directly related. We explore the
possible origins of these two emission components in the framework of a young,
non-accreting pulsar orbiting the massive star, and initiating the non-thermal
emission through the interaction of the stellar and pulsar winds. The
pulsar/stellar wind interaction in a compact orbit binary gives rise to two
potential locations for particle acceleration: the shocks at the head-on
collision of the winds and the termination shock caused by Coriolis forces on
scales larger than the binary separation. We explore the suitability of these
two locations to host the GeV and TeV emitters, respectively, through the study
of their non-thermal emission along the orbit. We focus on the application of
this model to LS 5039 given its well determined stellar wind with respect to
other gamma-ray binaries. The application of the proposed model to LS 5039
indicates that these two potential emitter locations provide the necessary
conditions for reproduction of the two-component high-energy gamma-ray spectrum
of LS 5039. In addition, the ambient postshock conditions required at each of
the locations are consistent with recent hydrodynamical simulations. The
scenario based on the interaction of the stellar and pulsar winds is compatible
with the GeV and TeV emission observed from gamma-ray binaries with unknown
compact objects, such as LS 5039 and LS I +61 303.Comment: Version as published in A&
Estudio de factibilidad para la instalaci贸n de una sala de internet al servicio de la comunidad samaria: cybernet ltda
El presente trabajo tiene como finalidad determinar la factibilidad de la instalaci贸n de una sala para el acceso a la Red Mundial de Informaci贸n, (CYBERNET LTDA.), puesta al servicio de la comunidad samaria, en la Avenida Libertador con Carrera 13 de esta ciudad es escaso, esto con el fin de brindarle facilidad en la obtenci贸n de la informaci贸n y de servicios tecnol贸gicos y as铆 lograr ampliar m谩s su conocimiento. Para la instalaci贸n de CYBERNET LTDA, se tienen en cuenta esquemas organizacionales propios de la microempresa, pero enfocando siempre factores claves como la eficiencia y calidad del servicio que se prestar谩, la atenci贸n y comodidad que se le debe brindar al cliente, as铆 como incentivos para dar a conocer el servicio, mediante promociones, publicidad etc
On the origin of correlated X-ray/VHE emission from LS I +61 303
The MAGIC collaboration has recently reported correlated X-ray and very high-energy gamma-ray emission from the gamma-ray binary LS I +61 303 during ~60% of one orbit. These observations suggest that the emission in these two bands has its origin in a single particle population. We aim at improving our understanding of the source behaviour by explaining the simultaneous X-ray and VHE data through a radiation model. We use a model based on a one zone population of relativistic leptonic particles assuming dominant adiabatic losses located at the position of the compact object. The adiabatic cooling timescale is inferred from the X-ray fluxes. The model can reproduce the spectra and lightcurves in the X-ray and VHE bands. Adiabatic losses could be the key ingredient to explain the X-ray and partially the VHE lightcurves. From the best fit result, we obtain a magnetic field of B=0.2 G, a minimum luminosity budget of ~2x10^35 erg/s and a relatively high acceleration efficiency. In addition, our results seem to confirm that the GeV emission detected by Fermi does not come from the same parent particle population as the X-ray and VHE emission and the Fermi spectrum poses a constraint on the hardness of the particle spectrum at lower energies. In the context of our scenario, more sensitive observations would allow to constrain the inclination angle, which could determine the nature of the compact object
Binaries with the eyes of CTA
The binary systems that have been detected in gamma rays have proven very useful to study high-energy processes, in particular particle acceleration, emission and radiation reprocessing, and the dynamics of the underlying magnetized flows. Binary systems, either detected or potential gamma-ray emitters, can be grouped in different subclasses depending on the nature of the binary components or the origin of the particle acceleration: the interaction of the winds of either a pulsar and a massive star or two massive stars; accretion onto a compact object and jet formation; and interaction of a relativistic outflow with the external medium. We evaluate the potentialities of an instrument like the Cherenkov telescope array (CTA) to study the non-thermal physics of gamma-ray binaries, which requires the observation of high-energy phenomena at different time and spatial scales. We analyze the capability of CTA, under different configurations, to probe the spectral, temporal and spatial behavior of gamma-ray binaries in the context of the known or expected physics of these sources. CTA will be able to probe with high spectral, temporal and spatial resolution the physical processes behind the gamma-ray emission in binaries, significantly increasing as well the number of known sources. This will allow the derivation of information on the particle acceleration and emission sites qualitatively better than what is currently available
The keV-TeV connection in gamma-ray binaries
[eng] Gamma-ray binaries are systems that comprise a young, massive star and a compact object that can be either a young pulsar or a black hole. They emit radiation from radio up to tens of TeV and show flux variability along the whole electromagnetic spectrum. For three of the four detected gamma-ray binaries, the nature of the compact object is unknown. In this thesis we present a study of gamma-ray binaries through three approaches that involve the simultaneous study of these sources in X-rays and very high energy (VHE) gamma-rays.
We present the discovery of correlated X-ray and VHE gamma-ray emission from LS I +61 303. The correlations indicates that the emission from these two bands could be originated in the same parent particle population, and we explore this idea through the calculation of a radiative model. This model allows us to significantly constrain the physical properties of the non-thermal emitter in LS I +61 303.
For those systems where the compact object is a young pulsar, the interaction between the stellar and pulsar winds will give rise to strong shocks. The shocked pulsar wind is the candidate location for non-thermal emission from these systems. The shocked stellar wind should give rise to a thermal X-ray spectrum, but no such features have been detected in the X-ray spectrum of gamma-ray binaries. We present a model of the thermal emission of the shocked stellar wind and use it to constrain the pulsar properties. We have applied this method to two X-ray observations of LS 5039 and have successfully constrained the pulsar spin-down luminosity.
Finally, we present a search for VHE emission from Scorpius X-1 through a simultaneous X-ray and VHE gamma-ray campaign. The X-ray observations allowed us to select black-hole states where non-thermal X-ray emission has been detected. We did not find significant VHE emission in any of the black hole states, but the upper limits derived will prove useful in future modelling of the non-thermal emitter in the source.[cat] Les bin脿ries de raigs gamma s贸n sistemes binaries formats per una estrella jove i massiva i un objecte compacte, que pot ser un p煤lsar jove o un forat negre, que emeten radiaci贸 fins a desenes de TeV i mostren variabilitat orbital en totes les bandes d'emissi贸, des de radio fins a raigs gamma. En el cas de tres de les quatre bin脿ries de raigs gamma detectades avui dia, se'n desconeix la natura de l'objecte compacte. En aquesta tesi presentem un estudi de les bin脿ries de raigs gamma mitjan莽ant tres treballs complementaris que involucren l'estudi simultani d'aquestes fonts en raigs X i raigs gamma de molt alta energia.
En primer lloc presentem el descobriment d'emissi贸 en raigs X i raigs gamma de molt alta energia correlades en el temps al sistema LS I +61 303. Aquesta correlaci贸 ens indica que l'emissi贸 en les dues bandes pot provenir d'una 煤nica poblaci贸 d'electrons, i ho confirmem mitjan莽ant la realitzaci贸 d'un model te貌ric de radiaci贸 que ens permet restringir significativament les propietats f铆siques de l'emissor no t猫rmic de la font.
En cas que la font energ猫tica dels sistemes sigui un p煤lsar, la interacci贸
entre els vents de l'estrella i el p煤lsar dona lloc a una regi贸 d'interacci贸
on el vent xocat del p煤lsar accelera part铆cules i emet des de radio fins a
raigs gamma. A l'espectre de raigs X, per貌, no es detecta l'emissi贸 t猫rmica
del vent xocat de l'estrella, que s'escalfa fins a desenes de milers de graus.
Aix貌 ens ha perm猫s estudiar la forma de la regi贸 d'interacci贸, determinada principalment per la pot猫ncia del p煤lsar, i fer un c脿lcul te貌ric de l'emissi贸 en raigs X t猫rmics. Hem aplicat aquest model al sistema LS 5039 i hem pogut determinar la pot猫ncia del p煤lsar, fet important per a la modelitzaci贸 de l'emissi贸 no t猫rmica de la font.
Finalment, presentem la cerca d'emissi贸 de raigs gamma provinent de sistemes binaris fins ara no detectats. Una campanya simult脿nia en raigs X i raigs gamma ens va permetre seleccionar les dades de molt alta energia del microqu脿sar Sco X-1 en funci贸 de l'estat d'acreci贸 sobre l'objecte compacte. Tot i no detectar la font en raigs gamma, els l铆mits superiors obtinguts permeten restringir les propietats f铆siques de Sco X-1 rellevants per a l'emissi贸 en molt alta energia
On the origin of correlated X-ray/VHE emission from LS I +61 303
The MAGIC collaboration has recently reported correlated X-ray and very high-energy gamma-ray emission from the gamma-ray binary LS I +61 303 during ~60% of one orbit. These observations suggest that the emission in these two bands has its origin in a single particle population. We aim at improving our understanding of the source behaviour by explaining the simultaneous X-ray and VHE data through a radiation model. We use a model based on a one zone population of relativistic leptonic particles assuming dominant adiabatic losses located at the position of the compact object. The adiabatic cooling timescale is inferred from the X-ray fluxes. The model can reproduce the spectra and lightcurves in the X-ray and VHE bands. Adiabatic losses could be the key ingredient to explain the X-ray and partially the VHE lightcurves. From the best fit result, we obtain a magnetic field of B=0.2 G, a minimum luminosity budget of ~2x10^35 erg/s and a relatively high acceleration efficiency. In addition, our results seem to confirm that the GeV emission detected by Fermi does not come from the same parent particle population as the X-ray and VHE emission and the Fermi spectrum poses a constraint on the hardness of the particle spectrum at lower energies. In the context of our scenario, more sensitive observations would allow to constrain the inclination angle, which could determine the nature of the compact object
An谩lisis a priori de una situaci贸n de optimizaci贸n en segundo de Educaci贸n Primaria
Resumen tomado de la publicaci贸nSe presenta una manera de introducir un problema de optimizaci贸n en el primer ciclo de Educaci贸n Primaria, mediante una transposici贸n did谩ctica que preserva la esencia de la optimizaci贸n en un contexto matem谩tico escolar propio de la etapa. Se afronta un problema de este tipo en el tr谩nsito del n煤mero natural a la medida, utilizando la ingenier铆a did谩ctica como m茅todo de investigaci贸n. En este marco se dise帽a una situaci贸n did谩ctica basada en el an谩lisis a priori. El objetivo de esta situaci贸n es doble: por un lado, la intervenci贸n razonada en los sistemas did谩cticos; por otra parte, producir conocimiento sobre la forma en la que se construyen y comunican problemas de optimizaci贸n relativos a la medida, en edad infantil.CantabriaES
Thermal X-Ray emission from the shocked stellar wind of pulsar gamma-ray binaries
Gamma-ray loud X-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds will collide producing broadband non-thermal emission, most likely originated in the shocked pulsar wind. Thermal X-ray emission is expected from the shocked stellar wind, but until now it has neither been detected nor studied in the context of gamma-ray binaries. We present a semi-analytic model of the thermal X-ray emission from the shocked stellar wind in pulsar gamma-ray binaries, and find that the thermal X-ray emission increases monotonically with the pulsar spin-down luminosity, reaching luminosities of the order of 10^33 erg/s. The lack of thermal features in the X-ray spectrum of gamma-ray binaries can then be used to constrain the properties of the pulsar and stellar winds. By fitting the observed X-ray spectra of gamma-ray binaries with a source model composed of an absorbed non-thermal power law and the computed thermal X-ray emission, we are able to derive upper limits on the spin-down luminosity of the putative pulsar. We applied this method to LS 5039, the only gamma-ray binary with a radial, powerful wind, and obtain an upper limit on the pulsar spin-down luminosity of ~6x10^36 erg/s. Given the energetic constraints from its high-energy gamma-ray emission, a non-thermal to spin-down luminosity ratio very close to unity may be required