Refine
Year of publication
- 2018 (2819) (remove)
Document Type
- Article (1775)
- Postprint (287)
- Doctoral Thesis (284)
- Other (195)
- Review (111)
- Monograph/Edited Volume (59)
- Part of a Book (23)
- Part of Periodical (21)
- Working Paper (19)
- Conference Proceeding (13)
Language
Keywords
- climate change (20)
- gamma rays: general (17)
- Germany (12)
- German (11)
- cosmic rays (11)
- permafrost (11)
- stars: massive (11)
- ISM: supernova remnants (10)
- adaptation (10)
- inflammation (9)
Institute
- Institut für Biochemie und Biologie (326)
- Institut für Geowissenschaften (314)
- Institut für Physik und Astronomie (312)
- Institut für Chemie (194)
- Mathematisch-Naturwissenschaftliche Fakultät (134)
- Department Psychologie (124)
- Institut für Umweltwissenschaften und Geographie (94)
- Department Sport- und Gesundheitswissenschaften (92)
- Institut für Ernährungswissenschaft (92)
- Hasso-Plattner-Institut für Digital Engineering GmbH (89)
- Department Linguistik (76)
- Institut für Mathematik (67)
- Institut für Romanistik (66)
- Wirtschaftswissenschaften (65)
- Zentrum für Lehrerbildung und Bildungsforschung (ZeLB) (61)
- Humanwissenschaftliche Fakultät (57)
- Historisches Institut (50)
- Sozialwissenschaften (47)
- Vereinigung für Jüdische Studien e. V. (47)
- Department Erziehungswissenschaft (43)
- Institut für Informatik und Computational Science (42)
- Bürgerliches Recht (41)
- Strukturbereich Kognitionswissenschaften (39)
- MenschenRechtsZentrum (36)
- Öffentliches Recht (26)
- Wirtschafts- und Sozialwissenschaftliche Fakultät (20)
- Institut für Germanistik (18)
- Extern (17)
- Institut für Jüdische Studien und Religionswissenschaft (17)
- Philosophische Fakultät (17)
- Berlin Potsdam Research Group "The International Rule of Law - Rise or Decline?" (16)
- Institut für Künste und Medien (16)
- Fachgruppe Politik- & Verwaltungswissenschaft (15)
- Fachgruppe Betriebswirtschaftslehre (13)
- Institut für Philosophie (13)
- Kommunalwissenschaftliches Institut (13)
- Department Musik und Kunst (12)
- Hasso-Plattner-Institut für Digital Engineering gGmbH (12)
- Institut für Anglistik und Amerikanistik (12)
- WeltTrends e.V. Potsdam (12)
- Fachgruppe Soziologie (11)
- Department für Inklusionspädagogik (10)
- Strafrecht (10)
- Klassische Philologie (9)
- Fachgruppe Volkswirtschaftslehre (7)
- Department Grundschulpädagogik (6)
- Juristische Fakultät (6)
- Referat für Presse- und Öffentlichkeitsarbeit (6)
- Universitätsbibliothek (6)
- Fakultät für Gesundheitswissenschaften (5)
- Institut für Slavistik (5)
- Strukturbereich Bildungswissenschaften (5)
- Potsdam Institute for Climate Impact Research (PIK) e. V. (4)
- Kanonistisches Institut e.V. (3)
- Hochschulambulanz (2)
- Moses Mendelssohn Zentrum für europäisch-jüdische Studien e. V. (2)
- Potsdam Research Institute for Multilingualism (PRIM) (2)
- Abraham Geiger Kolleg gGmbH (1)
- Akademie für Psychotherapie und Interventionsforschung GmbH (1)
- Deutsches MEGA-Konsortialbüro an der Universität Potsdam (1)
- Dezernat 2: Studienangelegenheiten (1)
- Forschungsbereich „Politik, Verwaltung und Management“ (1)
- Gesundheitsmanagement (1)
- Institut für Lebensgestaltung-Ethik-Religionskunde (1)
- Kanzler (1)
- Lehreinheit für Wirtschafts-Arbeit-Technik (1)
- Multilingualism (1)
- UP Transfer (1)
PKS 0625-354 (z = 0.055) was observed with the four High Energy Stereoscopic System (H.E.S.S.) telescopes in 2012 during 5.5 h. The source was detected above an energy threshold of 200 GeV at a significance level of 6.1 sigma. No significant variability is found in these observations. The source is well described with a power-law spectrum with photon index Gamma = 2.84 +/- 0.50(stat) +/- 0.10(syst) and normalization (at E-0 = 1.0 TeV) N-0(E-0)=(0.58 +/- 0.22(stat) +/- 0.12(syst)) x 10(-12) TeV-1 cm(-2) s(-1). Multiwavelength data collected with Fermi-LAT, Swift-XRT, Swift-UVOT, ATOM and WISE are also analysed. Significant variability is observed only in the Fermi-LAT gamma-ray and Swift-XRT X-ray energy bands. Having a good multiwavelength coverage from radio to very high energy, we performed a broad-band modelling from two types of emission scenarios. The results from a one zone lepto-hadronic and a multizone leptonic models are compared and discussed. On the grounds of energetics, our analysis favours a leptonic multizone model. Models associated to the X-ray variability constraint support previous results, suggesting a BL Lac nature of PKS 0625-354 with, however, a large-scale jet structure typical of a radio galaxy.
Spectral lines are among the most powerful signatures for dark matter (DM) annihilation searches in very-high-energy gamma rays. The central region of the Milky Way halo is one of the most promising targets given its large amount of DM and proximity to Earth. We report on a search for a monoenergetic spectral line from self-annihilations of DM particles in the energy range from 300 GeV to 70 TeV using a two-dimensional maximum likelihood method taking advantage of both the spectral and spatial features of the signal versus background. The analysis makes use of Galactic center observations accumulated over ten years (2004-2014) with the H.E.S.S. array of ground-based Cherenkov telescopes. No significant gamma-ray excess above the background is found. We derive upper limits on the annihilation cross section (sigma v) for monoenergetic DM lines at the level of 4 x 10(-28) cm(3) s(-1) at 1 TeV, assuming an Einasto DM profile for the Milky Way halo. For a DM mass of 1 TeV, they improve over the previous ones by a factor of 6. The present constraints are the strongest obtained so far for DM particles in the mass range 300 GeV-70 TeV. Ground-based gamma-ray observations have reached sufficient sensitivity to explore relevant velocity-averaged cross sections for DM annihilation into two gamma-ray photons at the level expected from the thermal relic density for TeV DM particles.
First ground-based measurement of sub-20 GeV to 100 GeV gamma-Rays from the Vela pulsar with HESS II
(2018)
Aims. We report on the measurement and investigation of pulsed high-energy y-ray emission from the Vela pulsar, PSR B0833-45, based on observations with the largest telescope of H.E.S.S., CT5, in monoscopic mode, and on data obtained with the Fermi-LAT. Methods. Data from 40.3 h of observations carried out with the H.E.S.S. II array from 2013 to 2015 have been used. A dedicated very low-threshold event reconstruction and analysis pipeline was developed to achieve the lowest possible energy threshold. Eight years of Fermi-LAT data were analysed and also used as reference to validate the CT5 telescope response model and analysis methods. Results. A pulsed gamma-ray signal at a significance level of more than 15 sigma is detected from the P2 peak of the Vela pulsar light curve. Of a total of 15 835 events, more than 6000 lie at an energy below 20 GeV, implying a significant overlap between H.E.S.S. II-CT5 and the Fermi-LAT. While the investigation of the pulsar light curve with the LAT confirms characteristics previously known up to 20 GeV in the tens of GeV energy range, CT5 data show a change in the pulse morphology of P2, i.e. an extreme sharpening of its trailing edge, together with the possible onset of a new component at 3.4 sigma significance level. Assuming a power-law model for the P2 spectrum, an excellent agreement is found for the photon indices (Gamma similar or equal to 4.1) obtained with the two telescopes above 10 GeV and an upper bound of 8% is derived on the relative offset between their energy scales. Using data from both instruments, it is shown however that the spectrum of P2 in the 10-100 GeV has a pronounced curvature; this is a confirmation of the sub-exponential cut-off form found at lower energies with the LAT. This is further supported by weak evidence of an emission above 100 GeV obtained with CT5. In contrast, converging indications are found from both CT5 and LAT data for the emergence of a hard component above 50 GeV in the leading wing (LW2) of P2, which possibly extends beyond 100 GeV. Conclusions. The detection demonstrates the performance and understanding of CT5 from 100 GeV down to the sub-20 GeV domain, i.e. unprecedented low energy for ground-based gamma-ray astronomy. The extreme sharpening of the trailing edge of the P2 peak found in the H.E.S.S. II light curve of the Vela pulsar and the possible extension beyond 100 GeV of at least one of its features, LW2, provide further constraints to models of gamma-Ray emission from pulsars.
Context. NGC 253 is one of only two starburst galaxies found to emit gamma-rays from hundreds of MeV to multi-TeV energies. Accurate measurements of the very-high-energy (VHE; E> 100 GeV) and high-energy (HE; E > 60 MeV) spectra are crucial to study the underlying particle accelerators, probe the dominant emission mechanism(s) and to study cosmic-ray interaction and transport. Aims. The measurement of the VHE gamma-ray emission of NGC 253 published in 2012 by H.E.S.S. was limited by large systematic uncertainties. Here, the most up to date measurement of the gamma-ray spectrum of NGC 253 is investigated in both HE and VHE gamma-rays. Assuming a hadronic origin of the gamma-ray emission, the measurement uncertainties are propagated into the interpretation of the accelerated particle population. Methods. The data of H.E.S.S. observations are reanalysed using an updated calibration and analysis chain. The improved Fermi-LAT analysis employs more than 8 yr of data processed using pass 8. The cosmic-ray particle population is evaluated from the combined HE-VHE gamma-ray spectrum using NAIMA in the optically thin case. Results. The VHE gamma-ray energy spectrum is best fit by a power-law distribution with a flux normalisation of (1.34 +/- 0.14(stat) +/- 0.27(sys)) x 10(-13) cm(-2) s(-1) TeV-1 at 1 TeV - about 40% above, but compatible with the value obtained in Abramowski et al. (2012). The spectral index Gamma = 2.39 +/- 0.14(stat) +/- 0.25(sys) is slightly softer than but consistent with the previous measurement within systematic errors. In the Fermi energy range an integral flux of F(E > 60 MeV) = (1.56 +/- 0.28(stat) +/- 0.15(sys)) x 10(-8) cm(-2) s(-1) is obtained. At energies above similar to 3 GeV the HE spectrum is consistent with a power-law ranging into the VHE part of the spectrum measured by H.E.S.S. with an overall spectral index Gamma = 2.22 +/- 0.06(stat). Conclusions. Two scenarios for the starburst nucleus are tested, in which the gas in the starburst nucleus acts as either a thin or a thick target for hadronic cosmic rays accelerated by the individual sources in the nucleus. In these two models, the level to which NGC 253 acts as a calorimeter is estimated to a range of f(cal) = 0.1 to 1 while accounting for the measurement uncertainties. The presented spectrum is likely to remain the most accurate measurements until the Cherenkov Telescope Array (CTA) has collected a substantial set of data towards NGC 253.
Dwarf spheroidal galaxies are among the most promising targets for detecting signals of Dark Matter (DM) annihilations. The H.E.S.S. experiment has observed five of these systems for a total of about 130 hours. The data are re-analyzed here, and, in the absence of any detected signals, are interpreted in terms of limits on the DM annihilation cross section. Two scenarios are considered: i) DM annihilation into mono-energetic gamma-rays and ii) DM in the form of pure WIMP multiplets that, annihilating into all electroweak bosons, produce a distinctive gamma-ray spectral shape with a high-energy peak at the DM mass and a lower-energy continuum. For case i), upper limits at 95% confidence level of about <sigma upsilon > less than or similar to 3 x 10(-25) cm(3) s(-1) are obtained in the mass range of 400 GeV to 1TeV. For case ii), the full spectral shape of the models is used and several excluded regions are identified, but the thermal masses of the candidates are not robustly ruled out.
Das Buch gibt Einblicke in das Strafrecht des real existierenden Sozialismus in Europa, insbesondere der DDR. Gespannt wird der Bogen von den philosophischen Ausgangspunkten im 19. Jahrhundert (Marx) über die rechtstheoretischen Debatten in der Sowjetunion in den 1920er Jahren und später in der DDR, und von dort weiter zur Strafpraxis, nämlich dem Wirtschaftsstrafrecht der DDR und der Todesstrafe als exemplarischen Feldern. Einblicke zu anderen Ländern des damaligen Warschauer Pakts geben Aufsätze über die Strafzumessung in Polen, den strafrechtlichen Lebensschutz in Ungarn und den tschechoslowakischen Straftatbestand der Ausschreitung. Anliegen ist es, durch die Profilierung des Theorie-Praxis-Bezugs ein vertieftes Verständnis dieses Strafrechtsdenkens zu unterstützen.
Mit Beiträgen von
Jochen Bung | Mihály Filó | Arnd Koch | Maciej Małolepszy | Pavel Raček | Georg Steinberg | Moritz Vormbaum | Jan Wintr | Benno Zabel | Sascha Ziemann
Reden ist Silber
(2018)
Wer klingelt?
(2018)
We present a catalogue of white dwarf candidates selected from the second data release of Gaia (DR2). We used a sample of spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey (SDSS) to map the entire space spanned by these objects in the Gaia Hertzsprung–Russell diagram. We then defined a set of cuts in absolute magnitude, colour, and a number of Gaia quality flags to remove the majority of contaminating objects. Finally, we adopt a method analogous to the one presented in our earlier SDSS photometric catalogues to calculate a probability of being a white dwarf (PWD) for all Gaia sources that passed the initial selection. The final catalogue is composed of 486641 stars with calculated PWD from which it is possible to select a sample of ≃260000 high-confidence white dwarf candidates in the magnitude range 8 < G < 21. By comparing this catalogue with a sample of SDSS white dwarf candidates, we estimate an upper limit in completeness of 85 per cent for white dwarfs with G ≤ 20 mag and Teff >7000 K, at high Galactic latitudes (|b| > 20°). However, the completeness drops at low Galactic latitudes, and the magnitude limit of the catalogue varies significantly across the sky as a function of Gaia’s scanning law. We also provide the list of objects within our sample with available SDSS spectroscopy. We use this spectroscopic sample to characterize the observed structure of the white dwarf distribution in the H–R diagram.
The presence of extreme horizontal branch (EHB) and blue hook stars in some Galactic globular clusters (GGCs) constitutes one of the remaining mysteries of stellar evolution. While several evolutionary scenarios have been proposed to explain the characteristics of this peculiar population of evolved stars, their observational verification has been limited by the availability of spectroscopic data for a statistically significant sample of such objects in any single GGC. We recently launched the SHOTGLAS project with the aim of providing a comprehensive picture of this intriguing stellar population in terms of spectroscopic properties for all readily accessible GGCs hosting an EHB. In this first paper, we focus on omega Cen, a peculiar, massive GGC that hosts multiple stellar populations. We use non-LTE model atmospheres to derive atmospheric parameters (Te ff, log g and N(He) / N(H)) and spectroscopic masses for 152 EHB stars in the cluster. This constitutes the largest spectroscopic sample of EHB stars ever analyzed in a GGC and represents similar to 20% of the EHB population of omega Cen. We also search for close binaries among these stars based on radial velocity variations. Our results show that the EHB population of omega Cen is divided into three spectroscopic groups that are very distinct in the Te ff helium abundance plane. The coolest sdB-type stars (Te ff. 30 000 K) have a hydrogen-rich atmosphere, populate the theoretical EHB region in the Te ff log g plane, and form 26% of our sample. The hottest sdO-type stars (Te ff & 42 000 K) make up 10% of the sample, have a hydrogen-rich atmosphere and are thought to be in a post-EHB evolutionary phase. The majority of our sample is found at intermediate temperatures and consists of sdOB stars that have roughly solar or super-solar atmospheric helium abundances. It is these objects that constitute the blue hook at V > 18 : 5 mag in the omega Cen color-magnitude diagram. Interestingly, the helium-enriched sdOBs do not have a significant counterpart population in the Galactic field, indicating that their formation is dependent on the particular environment found in omega Cen and other select GGCs. Another major di ff erence between the EHB stars in omega Cen and the field is the fraction of close binaries. From our radial velocity survey we identify two binary candidates, however no orbital solutions could be determined. We estimate an EHB close binary fraction of similar to 5% in omega Cen. This low fraction is in line with findings for other GGCs, but in sharp contrast to the situation in the field, where around 50% of the sdB stars reside in close binaries. Finally, the mass distribution derived is very similar for all three spectroscopic groups, however the average mass (0.38 M fi) is lower than that expected from stellar evolution theory. While this mass conundrum has previously been noted for EHB stars in omega Cen, it so far appears to be unique to that cluster.