Parameter constraints for high-energy models of colliding winds of massive stars: the case WR 147

We explore the ability of high energy observations to constrain orbital parameters of long period massive binary systems by means of an inverse Compton model acting in colliding wind environments. This is particular relevant for (very) long period binaries where orbital parameters are often poorly known from conventional methods, as is the case e.g. for the Wolf-Rayet (WR) star binary system WR 147 where INTEGRAL and MAGIC upper limits on the high-energy emission have recently been presented. We conduct a parameter study of the set of free quantities describing the yet vaguely constrained geometry and respective effects on the non-thermal high-energy radiation from WR 147. The results are confronted with the recently obtained high-energy observations and with sensitivities of contemporaneous high-energy instruments like Fermi-LAT. For binaries with sufficient long periods, like WR 147, gamma-ray attenuation is unlikely to cause any distinctive features in the high-energy spectrum. This leaves the anisotropic inverse Compton scattering as the only process that reacts sensitively on the line-of-sight angle with respect to the orbital plane, and therefore allows the deduction of system parameters even from observations not covering a substantial part of the orbit. Provided that particle acceleration acts sufficiently effectively to allow the production of GeV photons through inverse Compton scattering, our analysis indicates a preference for WR 147 to possess a large inclination angle. Otherwise, for low inclination angles, electron acceleration is constrained to be less efficient as anticipated here.Comment: 33 pages, 9 figures; accepted by Ap

TARGET: toward a solution for the readout electronics of the Cherenkov Telescope Array

TARGET is an application specific integrated circuit (ASIC) designed to read out signals recorded by the photosensors in cameras of very-high-energy gamma-ray telescopes exploiting the imaging of Cherenkov radiation from atmospheric showers. TARGET capabilities include sampling at a high rate (typically 1 GSample/s), digitization, and triggering on the sum of four adjacent pixels. The small size, large number of channels read out per ASIC (16), low cost per channel, and deep buffer for trigger latency (~16 $\mu$s at 1 GSample/s) make TARGET ideally suited for the readout in systems with a large number of telescopes instrumented with compact photosensors like multi-anode or silicon photomultipliers combined with dual-mirror optics. The possible advantages of such systems are better sensitivity, a larger field of view, and improved angular resolution. The two latest generations of TARGET ASICs, TARGET 5 and TARGET 7, are soon to be used for the first time in two prototypes of small-sized and medium-sized dual-mirror telescopes proposed in the framework of the Cherenkov Telescope Array (CTA) project. In this contribution we report on the performance of the TARGET ASICs and discuss future developments.Comment: 8 pages, 3 figures. In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions at arXiv:1508.0589

Status of Identification of VHE gamma-ray sources

With the recent advances made by Cherenkov telescopes such as H.E.S.S., the field of very high-energy (VHE) gamma-ray astronomy has recently entered a new era in which for the first time populations of Galactic sources such as e.g. Pulsar wind nebulae (PWNe) or Supernova remnants (SNRs) can be studied. However, while some of the new sources can be associated by positional coincidence as well as by consistent multi-wavelength data to a known counterpart at other wavelengths, most of the sources remain not finally identified. In the following, the population of Galactic H.E.S.S. sources will be used to demonstrate the status of the identifications, to classify them into categories according to this status and to point out outstanding problems.Comment: To appear in Astrophysics and Space Science (Proceedings of "The multimessenger approach to unidentified gamma-ray sources

Broad-band nonthermal emission from molecular clouds illuminated by cosmic rays from nearby supernova remnants

Molecular clouds are expected to emit non-thermal radiation due to cosmic ray interactions in the dense magnetized gas. Such emission is amplified if a cloud is located close to an accelerator of cosmic rays and if energetic particles can leave the accelerator site and diffusively reach the cloud. We consider here the situation in which a molecular cloud is located in the proximity of a supernova remnant which is efficiently accelerating cosmic rays and gradually releasing them in the interstellar medium. We calculate the multiwavelength spectrum from radio to gamma rays which is emerging from the cloud as the result of cosmic ray interactions. The total energy output is dominated by the gamma ray emission, which can exceed the emission in other bands by an order of magnitude or more. This suggests that some of the unidentified TeV sources detected so far, with no obvious or very weak counterparts in other wavelengths, might be in fact associated with clouds illuminated by cosmic rays coming from a nearby source. Moreover, under certain conditions, the gamma ray spectrum exhibit a concave shape, being steep at low energies and hard at high energies. This fact might have important implications for the studies of the spectral compatibility of GeV and TeV gamma ray sources.Comment: 13 pages, 6 figures, submitted to MNRA

Automatic Network Fingerprinting through Single-Node Motifs

Complex networks have been characterised by their specific connectivity patterns (network motifs), but their building blocks can also be identified and described by node-motifs---a combination of local network features. One technique to identify single node-motifs has been presented by Costa et al. (L. D. F. Costa, F. A. Rodrigues, C. C. Hilgetag, and M. Kaiser, Europhys. Lett., 87, 1, 2009). Here, we first suggest improvements to the method including how its parameters can be determined automatically. Such automatic routines make high-throughput studies of many networks feasible. Second, the new routines are validated in different network-series. Third, we provide an example of how the method can be used to analyse network time-series. In conclusion, we provide a robust method for systematically discovering and classifying characteristic nodes of a network. In contrast to classical motif analysis, our approach can identify individual components (here: nodes) that are specific to a network. Such special nodes, as hubs before, might be found to play critical roles in real-world networks.Comment: 16 pages (4 figures) plus supporting information 8 pages (5 figures

Der Bundestag ist gefordert wie nie: Was die jüngste Entscheidung des Bundesverfassungsgerichts für die weitere Wahlrechtsreform bedeutet

Das in sich etwas widersprüchliche Wahlgesetz der Ampelkoalition hat das Bundesverfassungsgericht am 30. Juli 2024 weitgehend bestätigt. Doch muss der Bundestag die gestrichene Grundmandatsklausel 2025 nochmals gelten lassen. Die Karlsruher Entscheidung ist ebenfalls nicht frei von Widersprüchen. Vor allem aber bedeutet sie einen Rückzug des Gerichts: Wahlsystematische Fragen könnten künftig keine Rolle mehr spielen in Karlsruhe. Und damit auch nicht die Frage, ob das Wahlsystem verständlich und nachvollziehbar ist. Der Bundestag ist dadurch aber nicht aus seiner Verantwortung entlassen, ein möglichst einfaches Wahlsystem zu beschließen. Ganz im Gegenteil: Das Parlament ist hier nun gefordert wie nie

Demokratie und Föderalismus: Kooperationsüberschuss und Mangel an Autonomie, oder: Die anderen machen es auch so

Während die Föderalismusreform von 2006 auf eine stärkere Entflechtung im bundesstaatlichen System zielte, zeigt sich mittlerweile wieder ein stärkerer Trend zum kooperativen Föderalismus. Die Entwicklungen im Parteiensystem verkomplizieren allerdings das Bund-Länder-Verhältnis. Ein Ausweg aus der dadurch schwieriger zu gestaltenden Politikverflechtung war zuletzt die stärkere Rolle der Ministerpräsidentenkonferenz parallel zum Bundesrat. Die immer buntere Koalitionslandschaft in Deutschland könnte dazu führen, dass Entflechtung der föderalen Ebenen doch wieder stärker zum Leitbild wird

Uneindeutig, halbherzig und verwirrend: Warum das Wahlgesetz der Ampel-Koalition kein Fortschritt ist

In diesem Meinungsbeitrag diskutiert der Autor die Reform des Wahlrechts kritisch und erläutert Parteienpositionen und -vorgehensweisen, grundlegende Begriffe (wie bspw. Überhangmandate, Direktmandate) sowie Alternativvorschläge zur Wahlrechtsreform

Ebola virus disease in the Democratic Republic of the Congo, 1976-2014: Figures and Data

The Democratic Republic of the Congo has experienced the most outbreaks of Ebola virus disease since the virus' discovery in 1976. This dataset contains details on all outbreaks in this country, comprising 996 cases. The study found that, compared to patients over 15 years old, the odds of dying were significantly lower in patients aged 5 to 15 and higher in children under five (with 100% mortality in those under 2 years old). The odds of dying increased by 11% per day that a patient was not hospitalised. Outbreaks with an initially high reproduction number, R (>3), were rapidly brought under control, whilst outbreaks with a lower initial R caused longer and generally larger outbreaks. These findings can inform the choice of target age groups for interventions and highlight the importance of both reducing the delay between symptom onset and hospitalisation and rapid national and international response