Narrow absorption features in the co-added XMM-Newton RGS spectra of isolated Neutron Stars

We co-added the available XMM-Newton RGS spectra for each of the isolated X-ray pulsars RX\,J0720.4$-$3125, RX\,J1308.6+2127 (RBS\,1223), RX\,J1605.3+3249 and RX\,J1856.4$-$3754 (four members of the "Magnificent Seven") and the "Three Musketeers" Geminga, PSR\,B0656+14 and PSR\,B1055-52. We confirm the detection of a narrow absorption feature at 0.57 keV in the co-added RGS spectra of RX\,J0720.4$-$3125 and RX\,J1605.3+3249 (including most recent observations). In addition we found similar absorption features in the spectra of RX\,J1308.6+2127 (at 0.53 keV) and maybe PSR\,B1055-52 (at 0.56 keV). The absorption feature in the spectra of RX\,J1308.6+2127 is broader than the feature e.g. in RX\,J0720.4$-$3125. The narrow absorption features are detected with 2$\sigma$ to 5.6$\sigma$ significance. Although very bright and frequently observed, there are no absorption features visible in the spectra of RX\,J1856.4$-$3754 and PSR\,B0656+14, while the co-added XMM-Newton RGS spectrum of Geminga has not enough counts to detect such a feature. We discuss a possible origin of these absorption features as lines caused by the presence of highly ionised oxygen (in particular OVII and/or OVI at 0.57 keV) in the interstellar medium and absorption in the neutron star atmosphere, namely the absorption features at 0.57 keV as gravitational redshifted ($g_{r}$=1.17) OVIII.Comment: 14 pages, 10 figures and 10 tables. Accepted for publication by MNRAS (Sep 12th, 2011

XMM-Newton reveals a candidate period for the spin of the "Magnificent Seven" neutron star RX J1605.3+3249

The group of thermally emitting isolated neutron stars (INSs) known as the "Magnificent Seven" (M7) is unique among the various neutron star populations. Crustal heating by means of magnetic field decay and an evolutionary link with magnetars may explain why these objects rotate more slowly and have higher thermal luminosities and magnetic field intensities than standard pulsars of similar age. The third brightest INS, RX J1605.3+3249, is the only object amidst the seven still lacking a detected periodicity. We observed the source with the XMM-Newton Observatory for 60 ks aiming at unveiling the neutron star rotation rate and investigating its spectrum in detail. A periodic signal at P=3.387864(16) s, most likely the neutron star spin period, is detected at the 4-sigma confidence level. The coherent combination of the new data with a past XMM-Newton EPIC-pn observation of the source constrains the pulsar spin-down rate at the 2-sigma confidence level, implying a dipolar magnetic field of B~7.4e13 G. If confirmed, RX J1605.3+3249 would be the neutron star with the highest dipolar field amongst the M7. The spectrum of the source shows evidence of a cool blackbody component, as well as for the presence of two broad absorption features. Furthermore, high-resolution spectroscopy with the RGS cameras confirms the presence of a narrow absorption feature at energy 0.57 keV in the co-added spectrum of the source, also seen in other thermally emitting isolated neutron stars. Phase-resolved spectroscopy, as well as a dedicated observing campaign aimed at determining a timing solution, will give invaluable constraints on the neutron star geometry and will allow one to confirm the high value of spin down, which would place the source closer to a magnetar than any other M7 INS.Comment: 12 pages, 6 figures; accepted for publication in A&A (revised version after language editing; results unchanged

Relatório de estágio em farmácia comunitária

Relatório de estágio realizado no âmbito do Mestrado Integrado em Ciências Farmacêuticas, apresentado à Faculdade de Farmácia da Universidade de Coimbr

Universal Dependencies 2.5

Universal Dependencies is a project that seeks to develop cross-linguistically consistent treebank annotation for many languages, with the goal of facilitating multilingual parser development, cross-lingual learning, and parsing research from a language typology perspective. The annotation scheme is based on (universal) Stanford dependencies (de Marneffe et al., 2006, 2008, 2014), Google universal part-of-speech tags (Petrov et al., 2012), and the Interset interlingua for morphosyntactic tagsets (Zeman, 2008)

Universal Dependencies 2.5

Universal Dependencies is a project that seeks to develop cross-linguistically consistent treebank annotation for many languages, with the goal of facilitating multilingual parser development, cross-lingual learning, and parsing research from a language typology perspective. The annotation scheme is based on (universal) Stanford dependencies (de Marneffe et al., 2006, 2008, 2014), Google universal part-of-speech tags (Petrov et al., 2012), and the Interset interlingua for morphosyntactic tagsets (Zeman, 2008)