Hard X-ray timing and spectral characteristics of the energetic pulsar PSR J0205+6449 in supernova remnant 3C58

PSR J0205+6449 is a young rotation-powered pulsar in SNR 3C 58. It is one of only three young (<10,000 year old) pulsars which are so far detected in the radio and the classical X-ray bands, as well as at hard X-rays above 20 keV and at high-energy (>100 MeV) $\gamma$-rays. The other two young pulsars are the Crab and PSR B1509-58. Our aim is to derive the timing and spectral characteristics of PSR J0205+6449 over the broad X-ray band from ~0.5 to ~270 keV. We used all publicly available RXTE observations of PSR J0205+6449 to first generate accurate ephemerides over the period September 30, 2000 - March 18, 2006. Next, phase-folding procedures yielded pulse profiles using data from RXTE PCA and HEXTE, and XMM-Newton EPIC PN. While our timing solutions are consistent with earlier results, our work shows sharper structures in the PCA X-ray profile. The X-ray pulse profile consists of two sharp pulses, separated in phase by 0.488(2), which can be described with 2 asymmetric Lorentzians, each with the rising wing steeper than the trailing wing, and full-width-half-maximum 1.41(5) ms and 2.35(22) ms, respectively. We find an indication for a flux increase by a factor ~2, about 3.5 sigma above the time-averaged value, for the second, weaker pulse during a two-week interval, while its pulse shape did not change. The spectrum of the pulsed X-ray emission is of non-thermal origin, exhibiting a power-law shape with photon index Gamma = 1.03(2) over the energy band ~0.5 to ~270 keV. In the energy band covered with the PCA (~3-30 keV) the spectra of the two pulses have the same photon index, namely, 1.04(3) and 1.10(8), respectively.Comment: 10 pages; 7 figures (2 in color), resubmitted to A&A, including referee comment

Anémonas anillo, una visión general (Cnidaria, Anthozoa, Actiniaria)

The present observations represent a new record of species of Actiniaria that are able to attach to a gorgonian branch by surrounding it with a solid piece of tissue junction and a significant reduction of the coelenteron. Ring sea anemones are provisionally placed in the Actinostolidae. They seem to be more common at depths between 85 and 1500 m., and according to our observations they are specialized to exclusively colonize on some species of gorgonians or pennatulaceans. Parasitism best describes the relationship between ring sea anemones and their hosts. We recognize five different species of ring sea anemones, one described by Hiles (1899) as Peronanthus verrucellae, and the others named by us provisionally as Peronanthus sp1, sp2, sp3 & sp4. The strategy displayed by ring sea anemones has several advantages, such as placement economy (see above), a better attachment against any current action, exploitation of food resources inaccessible to most other Actiniarians, and it allows them avoidance of habitat competition. The impossibility to colonize any other substrate but a certain group of gorgonians and a reduction of the gastric cavity are the main disadvantages detected in the ring sea anemones’ way of life. Apparently, this group of sea anemones is widespread through the Pacific Ocean.Un nuevo grupo de especies de actiniarios que desarrollan un nuevo sistema para afianzarse alrededor de los ejes de gorgonias y pennatuláceos es estudiado por nosotros en el presente trabajo. Se trata de un anillo de tejido que rodea los ejes y queda perfectamente sellado por medio de uniones del tejido produciendo una reducción del celenterón. Anémonas anillo es como las hemos denominado y provisionalmente han sido incluidas dentro de la familia Actinostolidae. Parece que son comunes en profundidades comprendidas entre los 85 y los 1500 metros, colonizando solamente determinadas especies de gorgonias y de pennatuláceos. El parasitismo es la relación que mejor describe lo que acontece entre las anémonas y los octocorales que la portan. Hay, al menos, cinco especies diferentes de anémonas anillo, la primera fue descrita por Hiles (1899) como Peronanthus verrucellae, las otras especies las denominamos provisionalmente como Peronanthus sp1, sp2, sp3 y sp4. El modo de vida de estas especies presenta ciertas ventajas como son: una reducción del espacio para asentarse, una mejor fijación frente a fenómenos de corriente, la capacidad para explotar recursos inaccesibles a la mayoría de los actiniarios y por último la falta de competencia con otras especies por el hábitat. La imposibilidad de colonizar otros sustratos y la reducción de la cavidad gástrica son las principales desventajas que presenta este modo de vida exhibido por las anémonas anillo. Aparentemente este grupo de anémonas está ampliamente distribuido en el Indo-Pacífico

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.

Optimising the multiplex factor of the frequency domain multiplexed readout of the TES-based microcalorimeter imaging array for the X-IFU instrument on the Athena Xray observatory

Athena is a space-based X-ray observatory intended for exploration of the hot and energetic universe. One of the science instruments on Athena will be the X-ray Integrated Field Unit (X-IFU), which is a cryogenic X-ray spectrometer, based on a large cryogenic imaging array of Transition Edge Sensors (TES) based microcalorimeters operating at a temperature of 100mK. The imaging array consists of 3800 pixels providing 2.5 eV spectral resolution, and covers a field of view with a diameter of of 5 arc minutes. Multiplexed readout of the cryogenic microcalorimeter array is essential to comply with the cooling power and complexity constraints on a space craft. Frequency domain multiplexing has been under development for the readout of TES-based detectors for this purpose, not only for the X-IFU detector arrays but also for TES-based bolometer arrays for the Safari instrument of the Japanese SPICA observatory. This paper discusses the design considerations which are applicable to optimise the multiplex factor within the boundary conditions as set by the space craft. More specifically, the interplay between the science requirements such as pixel dynamic range, pixel speed, and cross talk, and the space craft requirements such as the power dissipation budget, available bandwidth, and electromagnetic compatibility will be discussed