The loss-limited electron energy in SN 1006: effects of the shock velocity and of the diffusion process

The spectral shape of the synchrotron X-ray emission from SN 1006 reveals the fundamental role played by radiative losses in shaping the high-energy tail of the electron spectrum. We analyze data from the XMM-Newton SN 1006 Large Program and confirm that in both nonthermal limbs the loss-limited model correctly describes the observed spectra. We study the physical origin of the observed variations of the synchrotron cutoff energy across the shell. We investigate the role played by the shock velocity and by the electron gyrofactor. We found that the cutoff energy of the syncrotron X-ray emission reaches its maximum value in regions where the shock has experienced its highest average speed. This result is consistent with the loss-limited framework. We also find that the electron acceleration in both nonthermal limbs of SN 1006 proceeds close to the Bohm diffusion limit, the gyrofactor being in the range 1.5-4. We finally investigate possible explanations for the low values of cutoff energy measured in thermal limbs.Comment: Accepted for publication in Astronomische Nachrichten. Proceedings of the XMM-Newton Science Workshop 201

Grounding power on actions and mental attitudes

International audienceThe main objective of this work is to develop a logic called IAL (Intentional Agency Logic) in which we can reason about mental states of agents, action occurrences, and agentive and group powers. IAL will be exploited for a formal analysis of different forms of power such as an agent i's power of achieving a certain result and an agent i's power over another agent j (alias social power)

The shape of the cutoff in the synchrotron emission of SN 1006 observed with XMM-Newton

International audienceContext. Synchrotron X-ray emission from the rims of young supernova remnants allows us to study the high-energy tail of the electrons accelerated at the shock front.Aims. The analysis of X-ray spectra can provide information on the physical mechanisms that limit the energy achieved by the electrons in the acceleration process. We aim at verifying whether the maximum electron energy in SN 1006 is limited by synchrotron losses and at obtaining information on the shape of the cutoff in the X-ray synchrotron emission. Methods. We analyzed the deep observations of the XMM-Newton SN 1006 Large Program. We performed spatially resolved spectral analysis of a set of small regions in the nonthermal limbs and studied the X-ray spectra by adopting models that assume different electron spectra.Results. We found out that a loss-limited model provides the best fit to all the spectra and this indicates that the shape of the cutoff in the electron momentum (p) distribution has the form exp [ − (p/pcut)2]. We also detected residual thermal emission from shocked ambient medium and confirmed the reliability of previous estimates of the post-shock density.Conclusions. Our results indicate that radiative losses play a fundamental role in shaping the electron spectrum in SN 1006

The northwestern ejecta knot in SN 1006

International audienceAims. We want to probe the physics of fast collision-less shocks in supernova remnants. We are interested in the non-equilibration of temperatures and particle acceleration. Specifically, we aim to measure the oxygen temperature with regards to the electron temperature. In addition, we search for synchrotron emission in the northwestern thermal rim. Methods. This study is part of a dedicated deep observational project of SN 1006 using XMM-Newton, which provides us with the currently best resolution spectra of the bright northwestern oxygen knot. We aim to use the reflection grating spectrometer to measure the thermal broadening of the O vii line triplet by convolving the emission profile of the remnant with the response matrix.Results. The line broadening was measured as σe = 2.4 ± 0.3 eV, corresponding to an oxygen temperature of 275-63+72 keV. From the EPIC spectra we obtain an electron temperature of 1.35 ± 0.10 keV. The difference in temperature between the species provides further evidence of non-equilibration of temperatures in a shock. In addition, we find evidence of a bow shock that emits X-ray synchrotron radiation, which is at odds with the general idea that because of the magnetic field orientation only in the NE and SW region, X-ray synchrotron radiation should be emitted. We find an unusual Hα and X-ray synchrotron geometry, in that the Hα emission peaks downstream of the synchrotron emission. This may be an indication of a peculiar Hα shock in which the density is lower and the neutral fraction is higher than in other supernova remnants, resulting in a peak in Hα emission further downstream of the shock

X-raying hadronic acceleration at the SN 1006 shock front

Shock fronts in young supernova remnants are the best candidates for being sites of cosmic rays acceleration up to a few PeV, though conclusive experimental evidence is still lacking. Theoretical models predict that particle acceleration can modify the post-shock properties, e. g. by increasing the plasma density. We exploited the Large Program of deep XMM-Newton observations of SN 1006 to verify this prediction. We focused on the rim of the supernova remnant and by performing spatially resolved spectral analysis, we found that the shock compression ratio significantly increases in regions where particle acceleration is efficient, in agreement with expectations. Our results provide observational evidence for the presence of hadron acceleration processes at the SN 1006 shock front

Automating Agential Reasoning: Proof-Calculi and Syntactic Decidability for STIT Logics

This work provides proof-search algorithms and automated counter-model extraction for a class of STIT logics. With this, we answer an open problem concerning syntactic decision procedures and cut-free calculi for STIT logics. A new class of cut-free complete labelled sequent calculi G3LdmL^m_n, for multi-agent STIT with at most n-many choices, is introduced. We refine the calculi G3LdmL^m_n through the use of propagation rules and demonstrate the admissibility of their structural rules, resulting in auxiliary calculi Ldm^m_nL. In the single-agent case, we show that the refined calculi Ldm^m_nL derive theorems within a restricted class of (forestlike) sequents, allowing us to provide proof-search algorithms that decide single-agent STIT logics. We prove that the proof-search algorithms are correct and terminate

New distal marker closely linked to the fragile X locus

We have isolated II-10, a new X-chromosomal probe that identifies a highly informative two-allele TaqI restriction fragment length polymorphism at locus DXS466. Using somatic cell hybrids containing distinct portions of the long arm of the X chromosome, we could localize DXS466 between DXS296 and DXS304, both of which are closely linked distal markers for fragile X. This regional localization was supported by the analysis, in fragile X families, of recombination events between these three loci, the fragile X locus and locus DXS52, the latter being located at a more distal position. DXS466 is closely linked to the fragile X locus with a peak lod score of 7.79 at a recombination fraction of 0.02. Heterozygosity of DXS466 is approximately 50%. Its close proximity and relatively high informativity make DXS466 a valuable new diagnostic DNA marker for fragile X

XMM-Newton evidence of shocked ISM in SN 1006: indications of hadronic acceleration

Shock fronts in young supernova remnants are the best candidates for being sites of cosmic ray acceleration up to a few PeV, though conclusive experimental evidence is still lacking. Hadron acceleration is expected to increase the shock compression ratio, providing higher postshock densities, but X-ray emission from shocked ambient medium has not firmly been detected yet in remnants where particle acceleration is at work. We exploited the deep observations of the XMM-Newton Large Program on SN 1006 to verify this prediction. We performed spatially resolved spectral analysis of a set of regions covering the southeastern rim of SN 1006. We studied the spatial distribution of the thermodynamic properties of the ambient medium and carefully verified the robustness of the result with respect to the analysis method. We detected the contribution of the shocked ambient medium. We also found that the postshock density of the interstellar medium significantly increases in regions where particle acceleration is efficient. Under the assumption of uniform preshock density, we found that the shock compression ratio reaches a value of ~6 in regions near the nonthermal limbs. Our results support the predictions of shock modification theory and indicate that effects of acceleration of cosmic ray hadrons on the postshock plasma can be observed in supernova remnants.Comment: Accepted for publication in A&

Defeasible Logic: Agency, Intention and Obligation

We propose a computationally oriented non-monotonic multi-modal logic arising from the combination of agency, intention and obligation. We argue about the defeasible nature of these notions and then we show how to represent and reason with them in the setting of defeasible logic