| 1. |
- Joffrin, E., et al.
(författare)
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Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Forskningsöversikt (refereegranskat)abstract
- For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
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| 2. |
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| 3. |
- Murari, A., et al.
(författare)
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A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors
- 2024
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Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- The objective of thermonuclear fusion consists of producing electricity from the coalescence of light nuclei in high temperature plasmas. The most promising route to fusion envisages the confinement of such plasmas with magnetic fields, whose most studied configuration is the tokamak. Disruptions are catastrophic collapses affecting all tokamak devices and one of the main potential showstoppers on the route to a commercial reactor. In this work we report how, deploying innovative analysis methods on thousands of JET experiments covering the isotopic compositions from hydrogen to full tritium and including the major D-T campaign, the nature of the various forms of collapse is investigated in all phases of the discharges. An original approach to proximity detection has been developed, which allows determining both the probability of and the time interval remaining before an incoming disruption, with adaptive, from scratch, real time compatible techniques. The results indicate that physics based prediction and control tools can be developed, to deploy realistic strategies of disruption avoidance and prevention, meeting the requirements of the next generation of devices.
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| 4. |
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| 5. |
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| 6. |
- Acharya, B. S., et al.
(författare)
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Introducing the CTA concept
- 2013
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Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 43, s. 3-18
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. (C) 2013 Elsevier B.V. All rights reserved.
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| 7. |
- Actis, M., et al.
(författare)
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Design concepts for the Cherenkov Telescope Array CTA : an advanced facility for ground-based high-energy gamma-ray astronomy
- 2011
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Ingår i: Experimental astronomy. - : Springer. - 0922-6435 .- 1572-9508. ; 32:3, s. 193-316
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Tidskriftsartikel (refereegranskat)abstract
- Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA.
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| 8. |
- Singh, B. P., et al.
(författare)
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Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR
- 2015
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 51:8
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Tidskriftsartikel (refereegranskat)abstract
- Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (pi N) TDAs from (p) over barp -> e(+)e(-)pi(0) reaction with the future PANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q(2), the amplitude of the signal channel (p) over barp -> e(+)e(-)pi(0) admits a QCD factorized description in terms of pi N TDAs and nucleon Distribution Amplitudes (DAs) in the forward aid backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring (p) over barp -> e(+)e(-)pi(0) with the PANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. (p) over barp -> pi(+)pi(-)pi(0) were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q(2) < 4.3 GeV2 and 5 < q(2) < 9 GeV2, respectively, with a neutral pion scattered in the forward or backward cone vertical bar cos theta(pi 0)vertical bar > 0.5 in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the PANDA detector will allow to achieve a background rejection factor of 5 . 10(7) (1 . 10(7)) at low (high) q(2) for s = 5 GeV2, and of 1 . 10(8) (6 . 10(6)) at low (high) q(2) for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with PANDA will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing pi N TDAs.
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| 9. |
- Erni, W., et al.
(författare)
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Technical design report for the PANDA (AntiProton Annihilations at Darmstadt) Straw Tube Tracker
- 2013
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 49:2
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Tidskriftsartikel (refereegranskat)abstract
- This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.
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| 10. |
- Reimerdes, H., et al.
(författare)
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Overview of the TCV tokamak experimental programme
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 62:4
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Tidskriftsartikel (refereegranskat)abstract
- The tokamak a configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system to address critical issues in preparation for ITER and a fusion power plant. For the 2019-20 campaign its configurational flexibility has been enhanced with the installation of removable divertor gas baffles, its diagnostic capabilities with an extensive set of upgrades and its heating systems with new dual frequency gyrotrons. The gas baffles reduce coupling between the divertor and the main chamber and allow for detailed investigations on the role of fuelling in general and, together with upgraded boundary diagnostics, test divertor and edge models in particular. The increased heating capabilities broaden the operational regime to include T (e)/T (i) similar to 1 and have stimulated refocussing studies from L-mode to H-mode across a range of research topics. ITER baseline parameters were reached in type-I ELMy H-modes and alternative regimes with 'small' (or no) ELMs explored. Most prominently, negative triangularity was investigated in detail and confirmed as an attractive scenario with H-mode level core confinement but an L-mode edge. Emphasis was also placed on control, where an increased number of observers, actuators and control solutions became available and are now integrated into a generic control framework as will be needed in future devices. The quantity and quality of results of the 2019-20 TCV campaign are a testament to its successful integration within the European research effort alongside a vibrant domestic programme and international collaborations.
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| 11. |
- Margutti, R., et al.
(författare)
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A PANCHROMATIC VIEW OF THE RESTLESS SN 2009ip REVEALS THE EXPLOSIVE EJECTION OF A MASSIVE STAR ENVELOPE
- 2014
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 780:1
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Tidskriftsartikel (refereegranskat)abstract
- The double explosion of SN 2009ip in 2012 raises questions about our understanding of the late stages of massive star evolution. Here we present a comprehensive study of SN 2009ip during its remarkable rebrightenings. High-cadence photometric and spectroscopic observations from the GeV to the radio band obtained from a variety of ground-based and space facilities (including the Very Large Array, Swift, Fermi, Hubble Space Telescope, and XMM) constrain SN 2009ip to be a low energy (E similar to 1050 erg for an ejecta mass similar to 0.5 M-circle dot) and asymmetric explosion in a complex medium shaped by multiple eruptions of the restless progenitor star. Most of the energy is radiated as a result of the shock breaking out through a dense shell of material located at similar to 5 x 10(14) cm with M similar to 0.1 M-circle dot, ejected by the precursor outburst similar to 40 days before the major explosion. We interpret the NIR excess of emission as signature of material located further out, the origin of which has to be connected with documented mass-loss episodes in the previous years. Our modeling predicts bright neutrino emission associated with the shock break-out if the cosmic-ray energy is comparable to the radiated energy. We connect this phenomenology with the explosive ejection of the outer layers of the massive progenitor star, which later interacted with material deposited in the surroundings by previous eruptions. Future observations will reveal if the massive luminous progenitor star survived. Irrespective of whether the explosion was terminal, SN 2009ip brought to light the existence of new channels for sustained episodic mass loss, the physical origin of which has yet to be identified.
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| 12. |
- Bakker, D. C. E., et al.
(författare)
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An update to the surface ocean CO2 atlas (SOCAT version 2)
- 2014
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 6:1, s. 69-90
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Tidskriftsartikel (refereegranskat)abstract
- The Surface Ocean CO2 Atlas (SOCAT), an activity of the international marine carbon research community, provides access to synthesis and gridded fCO2 (fugacity of carbon dioxide) products for the surface oceans. Version 2 of SOCAT is an update of the previous release (version 1) with more data (increased from 6.3 million to 10.1 million surface water fCO 2 values) and extended data coverage (from 1968-2007 to 1968-2011). The quality control criteria, while identical in both versions, have been applied more strictly in version 2 than in version 1. The SOCAT website (http://www.socat.info/) has links to quality control comments, metadata, individual data set files, and synthesis and gridded data products. Interactive online tools allow visitors to explore the richness of the data. Applications of SOCAT include process studies, quantification of the ocean carbon sink and its spatial, seasonal, year-to-year and longerterm variation, as well as initialisation or validation of ocean carbon models and coupled climate-carbon models. © Author(s) 2014. CC Attribution 3.0 License.
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| 13. |
- Dunham, I, et al.
(författare)
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The DNA sequence of human chromosome 22
- 1999
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 402:6761, s. 489-495
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Tidskriftsartikel (refereegranskat)
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| 14. |
- Taddia, Francesco, et al.
(författare)
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The Carnegie Supernova Project II : The shock wave revealed through the fog : The strongly interacting Type IIn SN 2013L
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 638
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Tidskriftsartikel (refereegranskat)abstract
- We present ultra-violet (UV) to mid-infrared (MIR) observations of the long-lasting Type IIn supernova (SN) 2013L obtained by the Carnegie Supernova Project II beginning two days after discovery and extending until +887 days (d). The SN reached a peak r-band absolute magnitude of approximate to -19 mag and an even brighter UV peak, and its light curve evolution resembles that of SN 1988Z. The spectra of SN 2013L are dominated by hydrogen emission features, characterized by three components attributed to different emission regions. A unique feature of this Type IIn SN is that, apart from the first epochs, the blue shifted line profile is dominated by the macroscopic velocity of the expanding shock wave of the SN. We are therefore able to trace the evolution of the shock velocity in the dense and partially opaque circumstellar medium (CSM), from similar to 4800 km s(-1) at +48 d, decreasing as t(-0.23) to similar to 2700 km s(-1) after a year. We performed spectral modeling of both the broad- and intermediate-velocity components of the H alpha line profile. The high-velocity component is consistent with emission from a radially thin, spherical shell located behind the expanding shock with emission wings broadened by electron scattering. We propose that the intermediate component originates from preionized gas from the unshocked dense CSM with the same velocity as the narrow component, similar to 100 km s(-1), but also that it is broadened by electron scattering. These features provide direct information about the shock structure, which is consistent with model calculations. The spectra exhibit broad OI and [OI] lines that emerge at greater than or similar to +144 d and broad CaII features. The spectral continua and the spectral energy distributions (SEDs) of SN 2013L after +132 d are well reproduced by a two-component black-body (BB) model; one component represents emitting material with a temperature between 5 x 10(3) and 1.5 x 10(4) K (hot component) and the second component is characterized by a temperature around 1-1.5 x 10(3) K (warm component). The warm component dominates the emission at very late epochs (greater than or similar to +400 d), as is evident from both the last near infrared (NIR) spectrum and MIR observations obtained with the Spitzer Space Telescope. Using the BB fit to the SEDs, we constructed a bolometric light curve that was modeled together with the unshocked CSM velocity and the shock velocity derived from the H alpha line modeling. The circumstellar-interaction model of the bolometric light curve reveals a mass-loss rate history with large values (1.7x10(-2)-0.15 M-circle dot yr(-1)) over the similar to 25-40 years before explosion, depending on the radiative efficiency and anisotropies in the CSM. The drop in the light curve at similar to 350 days and the presence of electron scattering wings at late epochs indicate an anisotropic CSM. The mass-loss rate values and the unshocked-CSM velocity are consistent with the characteristics of a massive star, such as a luminous blue variable (LBV) undergoing strong eruptions, similar to eta Carinae. Our analysis also suggests a scenario where pre-existing dust grains have a distribution that is characterized by a small covering factor.
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| 15. |
- Taubenberger, S., et al.
(författare)
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SN2012dn from early to late times : 09dc-like supernovae reassessed
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 488:4, s. 5473-5488
-
Tidskriftsartikel (refereegranskat)abstract
- As a candidate super-Chandrasekhar' or 09dc-like TypeIa supernova (SNIa), SN 2012dn shares many characteristics with other members of this remarkable class of objects but lacks their extraordinary luminosity. Here, we present and discuss the most comprehensive optical data set of this SN to date, comprised of a densely sampled series of early-time spectra obtained within the Nearby Supernova Factory project, plus photometry and spectroscopy obtained at the Very Large Telescope about 1yr after the explosion. The light curves, colour curves, spectral time series, and ejecta velocities of SN 2012dn are compared with those of other 09dc-like and normal SNeIa, the overall variety within the class of 09dc-like SNeIa is discussed, and new criteria for 09dc-likeness are proposed. Particular attention is directed to additional insight that the late-phase data provide. The nebular spectra show forbidden lines of oxygen and calcium, elements that are usually not seen in late-time spectra of SNeIa, while the ionization state of the emitting iron plasma is low, pointing to low ejecta temperatures and high densities. The optical light curves are characterized by an enhanced fading starting similar to 60d after maximum and very low luminosities in the nebular phase, which is most readily explained by unusually early formation of clumpy dust in the ejecta. Taken together, these effects suggest a strongly perturbed ejecta density profile, which might lend support to the idea that 09dc-like characteristics arise from a brief episode of interaction with a hydrogen-deficient envelope during the first hours or days after the explosion.
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| 16. |
- Adlarson, Patrik, et al.
(författare)
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Abashian-Booth-Crowe Effect in Basic Double-Pionic Fusion : A New Resonance?
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:24, s. 242302-
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Tidskriftsartikel (refereegranskat)abstract
- We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn -> d pi(0)pi(0) over the full energy region of the ABC effect, a pronounced low-mass enhancement in the pi pi-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t- channel Delta Delta process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with m = 2.37 GeV, Gamma approximate to 70 MeV and I(J(P)) = 0(3(+)) in both pn and Delta Delta systems. Necessary further tests of the resonance interpretation are discussed.
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| 17. |
- Adolph, C, et al.
(författare)
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Measurement of the eta -> 3 pi(0) Dalitz plot distribution with the WASA detector at COSY
- 2009
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 677:1-2, s. 24-29
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Tidskriftsartikel (refereegranskat)abstract
- In the first production run of the WASA experiment at COSY, the eta decay into three neutral pions was measured in proton-proton interactions at a proton beam kinetic energy of 1.4 GeV. The Dalitz plot of the three pious was Studied using 1.2 x 10(5) fully reconstructed events. and the quadratic slope parameter alpha was determined to be -0.027 +/- 0.008(stat) +/- 0.005(syst). The result is consistent with previous measurements and further corroborates the importance of pion-pion final state interactions. (C) 2009 Elsevier B.V. All rights reserved.
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| 18. |
- Gal-Yam, A., et al.
(författare)
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A WC/WO star exploding within an expanding carbon-oxygen-neon nebula
- 2022
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 601:7892, s. 201-204
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Tidskriftsartikel (refereegranskat)abstract
- The final fate of massive stars, and the nature of the compact remnants they leave behind (black holes and neutron stars), are open questions in astrophysics. Many massive stars are stripped of their outer hydrogen envelopes as they evolve. Such Wolf-Rayet stars(1) emit strong and rapidly expanding winds with speeds greater than 1,000 kilometres per second. A fraction of this population is also helium-depleted, with spectra dominated by highly ionized emission lines of carbon and oxygen (types WC/WO). Evidence indicates that the most commonly observed supernova explosions that lack hydrogen and helium (types Ib/Ic) cannot result from massive WC/WO stars(2,3), leading some to suggest that most such stars collapse directly into black holes without a visible supernova explosion(4). Here we report observations of SN 2019hgp, beginning about a day after the explosion. Its short rise time and rapid decline place it among an emerging population of rapidly evolving transients(5-8). Spectroscopy reveals a rich set of emission lines indicating that the explosion occurred within a nebula composed of carbon, oxygen and neon. Narrow absorption features show that this material is expanding at high velocities (greater than 1,500 kilometres per second), requiring a compact progenitor. Our observations are consistent with an explosion of a massive WC/WO star, and suggest that massive Wolf-Rayet stars may be the progenitors of some rapidly evolving transients.
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| 19. |
- Adlarson, Patrik, et al.
(författare)
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Exclusive measurement of the eta -> pi(+) pi(-) gamma decay
- 2012
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 707:2, s. 243-249
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Tidskriftsartikel (refereegranskat)abstract
- An exclusive measurement of the decay eta -> pi(+) pi(-) gamma has been performed at the WASA facility at COSY. The eta mesons were produced in the fusion reaction pd -> He-3 X at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on 13 960 +/- 140 events after background subtraction. The measured pion angular distribution is consistent with a relative p-wave of the two-pion system, whereas the measured photon energy spectrum was found at variance with the simplest gauge invariant matrix element of eta -> pi(+) pi(-) gamma. A parameterization of the data can be achieved by the additional inclusion of the empirical pion vector form factor multiplied by a first-order polynomial in the squared invariant mass of the pi(+) pi(-) system.
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| 20. |
- Indebetouw, R., et al.
(författare)
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DUST PRODUCTION AND PARTICLE ACCELERATION IN SUPERNOVA 1987A REVEALED WITH ALMA
- 2014
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 782:1, s. 6-
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Tidskriftsartikel (refereegranskat)abstract
- Supernova (SN) explosions are crucial engines driving the evolution of galaxies by shock heating gas, increasing the metallicity, creating dust, and accelerating energetic particles. In 2012 we used the Atacama Large Millimeter/Submillimeter Array to observe SN 1987A, one of the best-observed supernovae since the invention of the telescope. We present spatially resolved images at 450 mu m, 870 mu m, 1.4 mm, and 2.8 mm, an important transition wavelength range. Longer wavelength emission is dominated by synchrotron radiation from shock-accelerated particles, shorter wavelengths by emission from the largest mass of dust measured in a supernova remnant (>0.2 M-circle dot). For the first time we show unambiguously that this dust has formed in the inner ejecta (the cold remnants of the exploded star's core). The dust emission is concentrated at the center of the remnant, so the dust has not yet been affected by the shocks. If a significant fraction survives, and if SN 1987A is typical, supernovae are important cosmological dust producers.
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| 21. |
- Kotak, R., et al.
(författare)
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Dust and The Type II-Plateau Supernova 2004et
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 704:1, s. 306-323
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Tidskriftsartikel (refereegranskat)abstract
- We present mid-infrared (MIR) observations of the Type II-plateau supernova (SN) 2004et, obtained with the Spitzer Space Telescope between 64 and 1406 days past explosion. Late-time optical spectra are also presented. For the period 300-795 days past explosion, we argue that the spectral energy distribution (SED) of SN 2004et comprises (1) a hot component due to emission from optically thick gas, as well as free-bound radiation; (2) a warm component due to newly formed, radioactively heated dust in the ejecta; and (3) a cold component due to an IR echo from the interstellar-medium dust of the host galaxy, NGC 6946. There may also have been a small contribution to the IR SED due to free-free emission from ionized gas in the ejecta. We reveal the first-ever spectroscopic evidence for silicate dust formed in the ejecta of a supernova. This is supported by our detection of a large, but progressively declining, mass of SiO. However, we conclude that the mass of directly detected ejecta dust grew to no more than a few times 10-4 M sun. We also provide evidence that the ejecta dust formed in comoving clumps of fixed size. We argue that, after about two years past explosion, the appearance of wide, box-shaped optical line profiles was due to the impact of the ejecta on the progenitor circumstellar medium and that the subsequent formation of a cool, dense shell was responsible for a later rise in the MIR flux. This study demonstrates the rich, multifaceted ways in which a typical core-collapse supernova and its progenitor can produce and/or interact with dust grains. The work presented here adds to the growing number of studies that do not support the contention that SNe are responsible for the large mass of observed dust in high-redshift galaxies.
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| 22. |
- Meixner, Margaret, et al.
(författare)
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Herschel and ALMA measurements of dust and molecules in supernova 1987A
- 2013
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Ingår i: Proceedings of Science. - 1824-8039. ; Part F113823
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Konferensbidrag (refereegranskat)abstract
- Dust production by supernovae is important in the dust life cycle of a galaxy. The explosion of SN 1987A was the nearest SN detected in the last 400 years, allowing us detailed studies of contemporary evolution of a supernova for the first time. In 2011, Matsuura et al. reported 0.4-0.7 M of dust in SN 1987A based on Herschel HERITAGE survey data, which is surprisingly large compared to prior measurements of supernovae. In this paper, we present our follow-up studies of this important discovery about SN 1987A using the Herschel Space Observatory and the Atacama Large Millimeter Array (ALMA). We highlight two important results, the detection of cold molecular gas and dust in the ejected material of SN 1987A. Our results suggest that SNe are significant producers of dust and molecules, as well as heavy elements, driving chemical evolution of galaxies.
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| 23. |
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| 24. |
- Adlarson, Patrik, et al.
(författare)
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Abashian-Booth-Crowe resonance structure in the double pionic fusion to He-4
- 2012
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 86:3, s. 032201-
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Tidskriftsartikel (refereegranskat)abstract
- Exclusive and kinematically complete high-statistics measurements of the double pionic fusion reaction dd -> He-4 pi(0)pi(0) have been performed in the energy range 0.8-1.4 GeV covering thus the region of the Abashian-Booth-Crowe effect, which denotes a pronounced low-mass enhancement in the pi pi invariant mass spectrum. The experiments were carried out with the WASA detector setup at the cooler synchrotron at Forshungszentrum Julich GmbH. Similar to the observation in the basic pn -> d pi(0)pi(0) reaction, the data reveal a correlation between the ABC effect and a resonancelike energy dependence in the total cross section. The maximum occurs at m = 2.37 GeV + 2m(N), i.e., at the same position as in the basic reaction. The observed resonance width Gamma approximate to 160 MeV can be understood from broadening due to Fermi motion of the nucleons in initial and final nuclei together with collision damping. Differential cross sections are described equally well by the hypothesis of a pn resonance formation during the reaction process.
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| 25. |
- Adlarson, Patrik, et al.
(författare)
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Investigation of the dd -> (3)Hen pi(0) reaction with the FZ Julich WASA-at-COSY facility
- 2013
-
Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 88:1, s. 014004-
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Tidskriftsartikel (refereegranskat)abstract
- An exclusive measurement of the dd -> (3)Hen pi(0) reaction was carried out at a beam momentum of p(d) = 1.2 GeV/c using the WASA-at-COSY facility. Information on the total cross section as well as differential distributions was obtained. The data are described by a phenomenological approach based on a combination of a quasifree model and a partial wave expansion for the three-body reaction. The total cross section is found to be sigma(tot) = ( 2.89 +/- 0.01(stat) +/- 0.06(sys) +/- 0.29(norm)) mu b. The contribution of the quasifree processes ( with the beam or target neutron being a spectator) accounts for 38% of the total cross section and dominates the differential distributions in specific regions of phase space. The remaining part of the cross section can be described by a partial wave decomposition indicating the significance of p-wave contributions in the final state.
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| 26. |
- Adlarson, Patrik, et al.
(författare)
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pi(0)pi(0) Production in proton-proton collisions at T-p=1.4 GeV The WASA-at-COSY Collaboration
- 2012
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 706:4-5, s. 256-262
-
Tidskriftsartikel (refereegranskat)abstract
- The reaction pp -> pp pi(0)pi(0) has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 +/- 21(systematic) +/- 58(normalization)) mu b. In order to study the production mechanism, differential kinematic distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Delta(1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N*(1440) via its decay into a proton and two pions is found.
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| 27. |
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| 28. |
- Berger, E., et al.
(författare)
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An Intermediate Luminosity Transient in NGC 300 : The Eruption of a Dust-Enshrouded Massive Star
- 2009
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 699, s. 1850-1865
-
Tidskriftsartikel (refereegranskat)abstract
- We present multi-epoch high-resolution optical spectroscopy, UV/radio/X-ray imaging, and archival Hubble and Spitzer observations of an intermediate luminosity optical transient recently discovered in the nearby galaxy NGC 300. We find that the transient (NGC 300 OT2008-1) has a peak absolute magnitude of M bol ≈ -11.8 mag, intermediate between novae and supernovae, and similar to the recent events M85 OT2006-1 and SN 2008S. Our high-resolution spectra, the first for this event, are dominated by intermediate velocity (~200-1000 km s-1) hydrogen Balmer lines and Ca II emission and absorption lines that point to a complex circumstellar environment, reminiscent of the yellow hypergiant IRC+10420. In particular, we detect asymmetric Ca II H&K absorption with a broad red wing extending to ~103 km s-1, indicative of gas inflow at high velocity (possibly the wind of a massive binary companion). The low luminosity, intermediate velocities, and overall similarity to a known eruptive star indicate that the event did not result in a complete disruption of the progenitor. We identify the progenitor in archival Spitzer observations, with deep upper limits from Hubble data. The spectral energy distribution points to a dust-enshrouded star with a luminosity of about 6 × 104 L sun, indicative of a ~10-20 M sun progenitor (or binary system). This conclusion is in good agreement with our interpretation of the outburst and circumstellar properties. The lack of significant extinction in the transient spectrum indicates that the dust surrounding the progenitor was cleared by the outburst. We thus predict that the progenitor should be eventually visible with Hubble if the transient event marks an evolutionary transition to a dust-free state, or with Spitzer if the event marks a cyclical process of dust formation.
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| 29. |
- Bolte, S., et al.
(författare)
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The Roots of Autism and ADHD Twin Study in Sweden (RATSS)
- 2014
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Ingår i: Twin Research and Human Genetics. - Stockholm : Cambridge University Press (CUP). - 1832-4274 .- 1839-2628. ; 17:3, s. 164-176
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Tidskriftsartikel (refereegranskat)abstract
- Neurodevelopmental disorders affect a substantial minority of the general population. Their origins are still largely unknown, but a complex interplay of genetic and environmental factors causing disturbances of the central nervous system's maturation and a variety of higher cognitive skills is presumed. Only limited research of rather small sample size and narrow scope has been conducted in neurodevelopmental disorders using a twin-differences design. The Roots of Autism and ADHD Twin Study in Sweden (RATSS) is an ongoing project targeting monozygotic twins discordant for categorical or dimensional autistic and inattentive/hyperactive-impulsive phenotypes as well as other neurodevelopmental disorders, and typically developing twin controls. Included pairs are 9 years of age or older, and comprehensively assessed for psychopathology, medical history, neuropsychology, and dysmorphology, as well as structural, functional, and molecular brain imaging. Specimens are collected for induced pluripotent (iPS) and neuroepithelial stem cells, genetic, gut bacteria, protein-/monoamine, and electron microscopy analyses. RATSS's objective is to generate a launch pad for novel surveys to understand the complexity of genotype-environment-phenotype interactions in autism spectrum disorder and attention-deficit hyperactivity disorder (ADHD). By October 2013, RATSS had collected data from 55 twin pairs, among them 10 monozygotic pairs discordant for autism spectrum disorder, seven for ADHD, and four for other neurodevelopmental disorders. This article describes the design, recruitment, data collection, measures, collected pairs' characteristics, as well as ongoing and planned analyses in RATSS. Potential gains of the study comprise the identification of environmentally mediated biomarkers, the emergence of candidates for drug development, translational modeling, and new leads for prevention of incapacitating outcomes.
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| 30. |
- Calén, H., et al.
(författare)
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Detector setup for a storage ring with an internal target
- 1996
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 379:1, s. 57-75
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Tidskriftsartikel (refereegranskat)abstract
- A detector setup for the cooler storage ring CELSIUS is described. The setup detects particles produced in interactions between the internal beam and a cluster-jet target. Particles emitted in the forward direction are measured by means of arrays of plastic scintillators and proportional counters. Particles, particularly photons, emitted more isotropically are measured by means of two calorimeters containing CsI(Na) crystals. The performance of the setup is given for neutral meson production in proton-proton and proton-deuteron interactions in the energy range 290-1360 MeV.
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| 31. |
- Greiner, J., et al.
(författare)
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GRIPS - Gamma-Ray Imaging, Polarimetry and Spectroscopy
- 2012
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Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 34:2, s. 551-582
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Tidskriftsartikel (refereegranskat)abstract
- We propose to perform a continuously scanning all-sky survey from 200 keV to 80 MeV achieving a sensitivity which is better by a factor of 40 or more compared to the previous missions in this energy range (COMPTEL, INTEGRAL; see Fig. 1). These gamma-ray observations will be complemented by observations in the soft X-ray and (near-)infrared region with the corresponding telescopes placed on a separate satellite. The Gamma-Ray Imaging, Polarimetry and Spectroscopy ("GRIPS") mission with its three instruments Gamma-Ray Monitor (GRM), X-Ray Monitor (XRM) and InfraRed Telescope (IRT) addresses fundamental questions in ESA's Cosmic Vision plan. Among the major themes of the strategic plan, GRIPS has its focus on the evolving, violent Universe, exploring a unique energy window. We propose to investigate γ-ray bursts and blazars, the mechanisms behind supernova explosions, nucleosynthesis and spallation, the enigmatic origin of positrons in our Galaxy, and the nature of radiation processes and particle acceleration in extreme cosmic sources including pulsars and magnetars. The natural energy scale for these non-thermal processes is of the order of MeV. Although they can be partially and indirectly studied using other methods, only the proposed GRIPS measurements will provide direct access to their primary photons. GRIPS will be a driver for the study of transient sources in the era of neutrino and gravitational wave observatories such as IceCUBE and LISA, establishing a new type of diagnostics in relativistic and nuclear astrophysics. This will support extrapolations to investigate star formation, galaxy evolution, and black hole formation at high redshifts.
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| 32. |
- Indebetouw, R., et al.
(författare)
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DUST PRODUCTION AND PARTICLE ACCELERATION IN SUPERNOVA 1987A REVEALED WITH ALMA
- 2014
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Ingår i: The Astrophysical Journal Letters. - : Institute of Physics (IOP). - 2041-8205. ; 782:1, s. L2-
-
Tidskriftsartikel (refereegranskat)abstract
- Supernova (SN) explosions are crucial engines driving the evolution of galaxies by shock heating gas, increasing the metallicity, creating dust, and accelerating energetic particles. In 2012 we used the Atacama Large Millimeter/Submillimeter Array to observe SN 1987A, one of the best-observed supernovae since the invention of the telescope. We present spatially resolved images at 450 mu m, 870 mu m, 1.4 mm, and 2.8 mm, an important transition wavelength range. Longer wavelength emission is dominated by synchrotron radiation from shock-accelerated particles, shorter wavelengths by emission from the largest mass of dust measured in a supernova remnant (>0.2 M-circle dot). For the first time we show unambiguously that this dust has formed in the inner ejecta (the cold remnants of the exploded star's core). The dust emission is concentrated at the center of the remnant, so the dust has not yet been affected by the shocks. If a significant fraction survives, and if SN 1987A is typical, supernovae are important cosmological dust producers.
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| 33. |
- Keleta, S, et al.
(författare)
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Exclusive measurement of two-pion production in the dd -> He-4 pi pi reaction
- 2009
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 825:1-2, s. 71-90
-
Tidskriftsartikel (refereegranskat)abstract
- The results from the first kinematically complete measurement of the dd -> He-4 pi pi reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar pi pi-invariant mass distributions appearing in double pion production in light ion collisions, the so-called ABC effect. The measurements were performed at the incident deuteron energies of 712 MeV and 1029 MeV. with the WASA detector assembly at CELSIUS in Uppsala, Sweden. We report the observation of a characteristic enhancement at low pi pi-invariant mass at 712 MeV, the lowest energy yet. At the higher energy, in addition to confirming previous experimental observations, Our results reveal a strong angular dependence of the pions in the overall centre of mass system. The results are qualitatively reproduced by a theoretical model, according to which the ABC effect is described as resulting from a kinematical enhancement in the production of the pion pairs from two parallel and independent NN -> d pi sub-processes. (C) 2009 Elsevier B.V. All rights reserved.
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| 34. |
- Lunnan, R., et al.
(författare)
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PS1-14bj : A HYDROGEN-POOR SUPERLUMINOUS SUPERNOVA WITH A LONG RISE AND SLOW DECAY
- 2016
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 831:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present photometry and spectroscopy of PS1-14bj, a hydrogen-poor superluminous supernova (SLSN) at redshift z = 0.5215 discovered in the last months of the Pan-STARRS1 Medium Deep Survey. PS1-14bj stands out because of its extremely slow evolution, with an observed rise of greater than or similar to 125 rest-frame days, and exponential decline out to similar to 250 days past peak at a measured rate of 0.01 mag day(-1), consistent with fully trapped Co-56 decay. This is the longest rise time measured in an SLSN to date, and the first SLSN to show a rise time consistent with pair-instability supernova (PISN) models. Compared to other slowly evolving SLSNe, it is spectroscopically similar to the prototype SN 2007bi at maximum light, although lower in luminosity (L-peak similar or equal to 4.6 x 10(43) erg s(-1) ) and with a flatter peak than previous events. PS1-14bj shows a number of peculiar properties, including a near-constant color temperature for > 200 days past peak, and strong emission lines from [O III] lambda 5007 and [O III] lambda 4363 with a velocity width of similar to 3400 km s(-1) in its late-time spectra. These both suggest there is a sustained source of heating over very long timescales, and are incompatible with a simple Ni-56-powered/PISN interpretation. A modified magnetar model including emission leakage at late times can reproduce the light curve, in which case the blue continuum and [O III] features are interpreted as material heated and ionized by the inner pulsar wind nebula becoming visible at late times. Alternatively, the late-time heating could be due to interaction with a shell of H-poor circumstellar material.
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| 35. |
- Matsuura, M., et al.
(författare)
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A STUBBORNLY LARGE MASS OF COLD DUST IN THE EJECTA OF SUPERNOVA 1987A
- 2015
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 800:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present new Herschel photometric and spectroscopic observations of Supernova 1987A, carried out in 2012. Our dedicated photometric measurements provide new 70 mu m data and improved imaging quality at 100 and 160 mu m compared to previous observations in 2010. Our Herschel spectra show only weak CO line emission, and provide an upper limit for the 63 mu m [O-I] line flux, eliminating the possibility that line contaminations distort the previously estimated dustmass. The far-infrared spectral energy distribution (SED) is well fitted by thermal emission from cold dust. The newly measured 70 mu m flux constrains the dust temperature, limiting it to nearly a single temperature. The far-infrared emission can be fitted by 0.5 +/- 0.1M(circle dot) of amorphous carbon, about a factor of two larger than the current nucleosynthetic mass prediction for carbon. The observation of SiO molecules at early and late phases suggests that silicates may also have formed and we could fit the SED with a combination of 0.3M(circle dot) of amorphous carbon and 0.5M(circle dot) of silicates, totalling 0.8M(circle dot) of dust. Our analysis thus supports the presence of a large dust reservoir in the ejecta of SN 1987A. The inferred dust mass suggests that supernovae can be an important source of dust in the interstellar medium, from local to high-redshift galaxies.
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| 36. |
- Matsuura, M., et al.
(författare)
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ALMA observations of Molecules in Supernova 1987A
- 2017
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Ingår i: Proceedings of the International Astronomical Union. - : Cambridge University Press. - 1743-9213 .- 1743-9221. ; :S331, s. 294-299
-
Tidskriftsartikel (refereegranskat)abstract
- Supernova (SN) 1987A has provided a unique opportunity to study how SN ejecta evolve in 30 years time scale. We report our ALMA spectral observations of SN 1987A, taken in 2014, 2015 and 2016, with detections of CO, 28SiO, HCO+ and SO, with weaker lines of 29SiO. We find a dip in the SiO line profiles, suggesting that the ejecta morphology is likely elongated. The difference of the CO and SiO line profiles is consistent with hydrodynamic simulations, which show that Rayleigh-Taylor instabilities causes mixing of gas, with heavier elements much more disturbed, making more elongated structure. Using 28SiO and its isotopologues, Si isotope ratios were estimated for the first time in SN 1987A. The estimated ratios appear to be consistent with theoretical predictions of inefficient formation of neutron rich atoms at lower metallicity, such as observed in the Large Magellanic Cloud (about half a solar metallicity). The deduced large HCO+ mass and small SiS mass, which are inconsistent to the predictions of chemical model, might be explained by some mixing of elements immediately after the explosion. The mixing might have made some hydrogen from the envelope to sink into carbon and oxygen-rich zone during early days after the explosion, enabling the formation of a substantial mass of HCO+. Oxygen atoms may penetrate into silicon and sulphur zone, suppressing formation of SiS. Our ALMA observations open up a new window to investigate chemistry, dynamics and explosive-nucleosynthesis in supernovae.
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| 37. |
- Meikle, W. P. S., et al.
(författare)
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A Spitzer Space Telescope Study of SN 2002hh : An Infrared Echo from a Type IIP Supernova
- 2006
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 649, s. 332-344
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Tidskriftsartikel (refereegranskat)abstract
- We present late-time (590-994 days) mid-IR photometry of the normal but highly reddened Type IIP supernova SN 2002hh. Bright, cool, slowly fading emission is detected from the direction of the supernova. Most of this flux appears not to be driven by the supernova event but instead probably originates in a cool, obscured star formation region or molecular cloud along the line of sight. We also show, however, that the declining component of the flux is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR emission could also be coming from newly condensed dust and/or an ejecta/CSM impact, but their contributions are likely to be small. For the case of a CSM-IR echo, we infer a dust mass of as little as 0.036 Msolar with a corresponding CSM mass of 3.6(0.01/rdg) Msolar, where rdg is the dust-to-gas mass ratio. Such a CSM would have resulted from episodic mass loss whose rate declined significantly about 28,000 years ago. Alternatively, an IR echo from a surrounding, dense, dusty molecular cloud might also have been responsible for the fading component. Either way, this is the first time that an IR echo has been clearly identified in a Type IIP supernova. We find no evidence for or against the proposal that Type IIP supernovae produce large amounts of dust via grain condensation in the ejecta. However, within the CSM-IR echo scenario, the mass of dust derived implies that the progenitors of the most common of core-collapse supernovae may make an important contribution to the universal dust content.
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| 38. |
- Meikle, W. P. S., et al.
(författare)
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Dust and the type II-Plateau supernova 2004dj
- 2011
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 732:2, s. 109-
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Tidskriftsartikel (refereegranskat)abstract
- We present mid-infrared (MIR) spectroscopy of a Type II-plateau supernova, SN 2004dj, obtained with the Spitzer Space Telescope, spanning 106-1393 days after explosion. MIR photometry plus optical/near-IR observations are also reported. An early-time MIR excess is attributed to emission from non-silicate dust formed within a cool dense shell (CDS). Most of the CDS dust condensed between 50 days and 165 days, reaching a mass of 0.3 x 10(-5) M(circle dot). Throughout the observations, much of the longer wavelength (> 10 mu m) part of the continuum is explained as an IR echo from interstellar dust. The MIR excess strengthened at later times. We show that this was due to thermal emission from warm, non-silicate dust formed in the ejecta. Using optical/near-IR line profiles and the MIR continua, we show that the dust was distributed as a disk whose radius appeared to be shrinking slowly. The disk radius may correspond to a grain destruction zone caused by a reverse shock which also heated the dust. The dust-disk lay nearly face-on, had high opacities in the optical/near-IR regions, but remained optically thin in the MIR over much of the period studied. Assuming a uniform dust density, the ejecta dust mass by 996 days was (0.5 +/- 0.1) x 10(-4) M(circle dot) and exceeded 10(-4) M(circle dot) by 1393 days. For a dust density rising toward the center the limit is higher. Nevertheless, this study suggests that the amount of freshly synthesized dust in the SN 2004dj ejecta is consistent with that found from previous studies and adds further weight to the claim that such events could not have been major contributors to the cosmic dust budget.
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| 39. |
- Perez-Torres, Miguel Angel, et al.
(författare)
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Constraining the progenitor of the type Ia SN 2014J with the EVN and eMERLIN
- 2014
-
Ingår i: Proceedings of Science. - 1824-8039.
-
Konferensbidrag (refereegranskat)abstract
- We report the deepest radio interferometric observations of the closest Type Ia supernova in decades, SN 2014J, which exploded in the nearby galaxy M 82. These observations represent, together with radio observations of SNe 2011fe, the most sensitive radio studies of a Type Ia SN ever. We constrain the mass-loss rate from the progenitor system of SN 2014J to M ≲ 7.0 × 10-10 M⊙yr-1 (for a wind speed of 100 km s-1). Most single-degenerate scenarios, i.e., the wide family of progenitor systems where a red giant, main-sequence, or sub-giant star donates mass to a exploding white dwarf, are ruled out by our observations. On the contrary, our stringent upper limits to the radio emission from SN 2014 favor a double-degenerate scenario-involving two WD stars-for the progenitor system of SN 2014J, as such systems have less circumstellar gas than our upper limits. Thus, the evidence from SNe 2011fe and 2014J points in the direction of a double-degenerate scenario for both. Looking into the future, we note that the huge improvement in sensitivity of the SKA with respect to its predecessors will allow us to determine which progenitor scenario (single-degenerate vs. double-degenerate) applies to a large sample of nearby Type Ia SNe, thus unambiguously solving this issue. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
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| 40. |
- Perez-Torres, Miguel Angel, et al.
(författare)
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Constraints on the Progenitor System and the Environs of SN 2014J from Deep Radio Observations
- 2014
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 792:1, s. Art. no. 38-
-
Tidskriftsartikel (refereegranskat)abstract
- We report deep EVN and eMERLIN observations of the Type Ia SN 2014J in the nearby galaxy M82. Our observations represent, together with JVLA observations of SNe 2011fe and 2014J, the most sensitive radio studies of Type Ia SNe ever. By combining data and a proper modeling of the radio emission, we constrain the mass-loss rate from the progenitor system of SN 2014J to (M) over dot less than or similar to 7.0 x 10(-10) M yr(-1) (for a wind speed of 100 km s(-1)). If the medium around the supernova is uniform, then n(ISM) less than or similar to 1.3 cm(-3), which is the most stringent limit for the (uniform) density around a Type Ia SN. Our deep upper limits favor a double-degenerate (DD) scenario-involving two WD stars-for the progenitor system of SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast, most single-degenerate (SD) scenarios, i.e., the wide family of progenitor systems where a red giant, main-sequence, or sub-giant star donates mass to an exploding WD, are ruled out by our observations. (While completing our work, we noticed that a paper by Margutti et al. was submitted to The Astrophysical Journal. From a non-detection of X-ray emission from SN 2014J, the authors obtain limits of (M) over dot less than or similar to 1.2 x 10(-9) M-circle dot yr(-1) (for a wind speed of 100 km s(-1)) and n(ISM) less than or similar to 3.5 cm(-3), for the rho proportional to r(-2) wind and constant density cases, respectively. As these limits are less constraining than ours, the findings by Margutti et al. do not alter our conclusions. The X-ray results are, however, important to rule out free-free and synchrotron self-absorption as a reason for the radio non-detections.) Our estimates on the limits on the gas density surrounding SN2011fe, using the flux density limits from Chomiuk et al., agree well with their results. Although we discuss the possibilities of an SD scenario passing observational tests, as well as uncertainties in the modeling of the radio emission, the evidence from SNe 2011fe and 2014J points in the direction of a DD scenario for both.
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| 41. |
- Perez-Torres, Miguel Angel, et al.
(författare)
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What is the progenitor of the Type Ia SN 2014J?
- 2014
-
Ingår i: Proceedings of the 11th Scientific Meeting of the Spanish Astronomical Society - Highlights of Spanish Astrophysics VIII, SEA 2014. ; , s. 540-546
-
Konferensbidrag (refereegranskat)abstract
- We report the deepest radio interferometric observations of the closest Type Ia supernova in decades, SN 2014J, which exploded in the nearby galaxy M 82. These observations represent, together with radio observations of SNe 2011fe, the most sensitive radio studies of a Type Ia SN ever. We constrain the mass-loss rate from the progenitor system of SN 2014J lower than 7.0 × 10^(−10) M yr^(−1) (for a wind speed of 100 km s^(−1) ). Our deep upper limits favor a double-degenerate scenario–involving two WD stars–for the progenitor system of SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast, most single-degenerate scenarios, i.e., the wide family of progenitor systems where a red giant, main-sequence, or sub-giant star donates mass to a exploding white dwarf, are ruled out by our observations. The evidence from SNe 2011fe and 2014J points in the direction of a double-degenerate scenario for both.
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| 42. |
- Schonning, K., et al.
(författare)
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The pd -> He-3 eta pi(0) reaction at T-p=1450 MeV CELSIUS/WASA Collaboration
- 2010
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 685:1, s. 33-37
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Tidskriftsartikel (refereegranskat)abstract
- The cross section for the pd -> He-3 eta pi(0) reaction has been measured at a beam energy of 1450 MeV using the WASA detector at the CELSIUS storage ring. The He-3 was detected in coincidence with four photons from the decays of the two mesons. The data indicate that the production mechanism involves the formation of the Delta(1232) isobar. Although the beam energy does not allow the full peak of this resonance to be seen, the invariant mass distributions Of all three pairs of final particles are well reproduced by a phase space Monte Carlo simulation weighted with the p-wave factor of the square of the pi(0) momentum in the He-3 pi(0) system.
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| 43. |
- Schönning, Karin, et al.
(författare)
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Production of the omega meson in the pd -> He-3 omega reaction at 1450 MeV and 1360 MeV
- 2009
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 79:4, s. 044002-
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Tidskriftsartikel (refereegranskat)abstract
- The production of omega mesons in the pd -> He-3 omega reaction has been studied at two energies near the kinematic threshold, T-p = 1450 MeV and T-p = 1360 MeV. The differential cross section was measured as a function of the omega c.m. angle at both energies over the whole angular range. Whereas the results at 1360 MeV are consistent with isotropy, strong rises are observed near both the forward and backward directions at 1450 MeV. Calculations made using a two-step model with an intermediate pion fail to reproduce the shapes of the measured angular distributions and also underestimate the total cross sections.
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| 44. |
- Sollerman, Jesper, et al.
(författare)
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Two stripped envelope supernovae with circumstellar interaction : But only one really shows it
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 643
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Tidskriftsartikel (refereegranskat)abstract
- Context. We present observations of SN 2019tsf (ZTF19ackjszs) and SN 2019oys (ZTF19abucwzt). These two stripped envelope (SE) Type Ib supernovae (SNe) suddenly showed a (re-)brightening in their late light curves. We investigate this in the context of circumstellar material (CSM) interaction with previously ejected material, a phenomenon that is unusual among SE SNe.Aims. We use our follow-up photometry and spectroscopy for these supernovae to demonstrate the presence of CSM interaction, estimate the properties of the CSM, and discuss why the signals are so different for the two objects.Methods. We present and analyze observational data, consisting of optical light curves and spectra. For SN 2019oys, we also have detections in radio as well as limits from UV and X-rays.Results. Both light curves show spectacular re-brightening after about 100 days. In the case of SN 2019tsf, the re-brightening is followed by a new period of decline, and the spectra never show signs of narrow emission lines that would indicate CSM interaction. On the contrary, SN 2019oys made a spectral makeover from a Type Ib to a spectrum clearly dominated by CSM interaction at the light curve brightening phase. Deep Keck spectra reveal a plethora of narrow high-ionization lines, including coronal lines, and the radio observations show strong emission.Conclusions. The rather similar light curve behavior – with a late linear re-brightening – of these two Type Ib SE SNe indicate CSM interaction as the powering source. For SN 2019oys the evidence for a phase where the ejecta hit H-rich material, likely ejected from the progenitor star, is conspicuous. We observe strong narrow lines of H and He, but also a plethora of high-ionization lines, including coronal lines, revealing shock interaction. Spectral simulations of SN 2019oys show two distinct density components, one with density ≳109 cm−3, dominated by somewhat broader, low-ionization lines of H I, He I, Na I, and Ca II, and one with narrow, high-ionization lines at a density ∼106 cm−3. The former is strongly affected by electron scattering, while the latter is unaffected. The evidence for CSM interaction in SN 2019oys is corroborated by detections in radio. On the contrary, for SN 2019tsf, we find little evidence in the spectra for any CSM interaction.
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| 45. |
- Tala, T., et al.
(författare)
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Density peaking in JET-determined by fuelling or transport?
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:12
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Tidskriftsartikel (refereegranskat)abstract
- Core density profile peaking and electron particle transport have been extensively studied by performing several dimensionless collisionality (upsilon*) scans with other matched dimensionless profiles in various plasma operation scenarios on the Joint European Torus (JET). This is the first time when electron particle transport coefficients in the H-mode have been measured on JET with high resolution diagnostics, and therefore we are in a position to distinguish between the neutral beam injection (NBI) source and inward electron particle pinch in contributing to core density peaking. The NBI particle source is found to contribute typically 50%-60% to the electron density peaking in JET H-mode plasmas where T-e/T-i similar to 1 or smaller and at upsilon* = 0.1-0.5 (averaged between r/a = 0.3-0.8), and being independent of upsilon* within that range. In these H-mode plasmas, the electron particle transport coefficients, D-e and v(e), are small, thus giving rise to the large influence of NBI fueling with respect to transport effect on peaking. In L-mode plasma conditions, the role of the NBI source is small, typically 10%-20%, and the electron particle transport coefficients are large. These dimensionless upsilon* scans give the best possible data for model validation. TGLF simulations are in good agreement with the experimental results with respect to the role of NBI particle source versus inward pinch in affecting density peaking, both for the H-mode and L-mode upsilon* scans. It predicts, similarly to experimental results, that typically about half of the peaking originates from the NBI fuelling in the H-mode and 10%-20% in the L-mode. GENE simulation results also support the key role of NBI fuelling in causing a peaked density profile in JET H-mode plasma (T-e/T-i similar to 1 and upsilon* = 0.1-0.5) and, in fact, give an even higher weight on NBI fuelling than that experimentally observed or predicted by TGLF. For the non-fuelled H-mode plasma at higher T-e/T-i = 1.5 and lower beta(N) and upsilon*, both TGLF and GENE predict peaked density profiles, therefore agreeing well with experimental steady-state density peaking. Overall, the various modelling results give a fairly good confidence in using TGLF and GENE in predicting density peaking in quite a wide range of plasma conditions in JET.
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| 46. |
- Wang, Xiaofeng, et al.
(författare)
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Evidence for type ia supernova diversity from ultraviolet observations with the hubble space telescope
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 749:2, s. 126-
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Tidskriftsartikel (refereegranskat)abstract
- We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This data set provides unique spectral time series down to 2000 angstrom. Significant diversity is seen in the near-maximum-light spectra (similar to 2000-3500 angstrom) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminositiesmeasured in the uvw1/F250W filter are found to correlate with the B-band light-curve shape parameter Delta m(15)(B), but with much larger scatter relative to the correlation in the broadband B band (e.g., similar to 0.4 mag versus similar to 0.2 mag for those with 0.8 mag < Delta m(15)(B) < 1.7 mag). SN 2004dt is found as an outlier of this correlation (at > 3 sigma), being brighter than normal SNe Ia such as SN 2005cf by similar to 0.9 mag and similar to 2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.
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| 47. |
- Abe, C., et al.
(författare)
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Genetic risk for bipolar disorder and schizophrenia predicts structure and function of the ventromedial prefrontal cortex
- 2021
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Ingår i: Journal of Psychiatry & Neuroscience. - : CMA Joule Inc.. - 1180-4882 .- 1488-2434. ; 46:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Bipolar disorder is highly heritable and polygenic. The polygenic risk for bipolar disorder overlaps with that of schizophrenia, and polygenic scores are normally distributed in the population. Bipolar disorder has been associated with structural brain abnormalities, but it is unknown how these are linked to genetic risk factors for psychotic disorders. Methods: We tested whether polygenic risk scores for bipolar disorder and schizophrenia predict structural brain alterations in 98 patients with bipolar disorder and 81 healthy controls. We derived brain cortical thickness, surface area and volume from structural MRI scans. In post-hoc analyses, we correlated polygenic risk with functional hub strength, derived from resting-state functional MRI and brain connectomics. Results: Higher polygenic risk scores for both bipolar disorder and schizophrenia were associated with a thinner ventromedial prefrontal cortex (vmPFC). We found these associations in the combined group, and separately in patients and drug-naive controls. Polygenic risk for bipolar disorder was correlated with the functional hub strength of the vmPFC within the default mode network. Limitations: Polygenic risk is a cumulative measure of genomic burden. Detailed genetic mechanisms underlying brain alterations and their cognitive consequences still need to be determined. Conclusion: Our multimodal neuroimaging study linked genomic burden and brain endophenotype by demonstrating an association between polygenic risk scores for bipolar disorder and schizophrenia and the structure and function of the vmPFC. Our findings suggest that genetic factors might confer risk for psychotic disorders by influencing the integrity of the vmPFC, a brain region involved in self-referential processes and emotional regulation. Our study may also provide an imaging-genetics vulnerability marker that can be used to help identify individuals at risk for developing bipolar disorder.
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| 48. |
- Abellán, F. J., et al.
(författare)
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Very Deep inside the SN 1987A Core Ejecta : Molecular Structures Seen in 3D
- 2017
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Ingår i: Astrophysical Journal Letters. - : Institute of Physics Publishing. - 2041-8205 .- 2041-8213. ; 842:2
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Tidskriftsartikel (refereegranskat)abstract
- Most massive stars end their lives in core-collapse supernova explosions and enrich the interstellar medium with explosively nucleosynthesized elements. Following core collapse, the explosion is subject to instabilities as the shock propagates outward through the progenitor star. Observations of the composition and structure of the innermost regions of a core-collapse supernova provide a direct probe of the instabilities and nucleosynthetic products. SN 1987A in the Large Magellanic Cloud is one of very few supernovae for which the inner ejecta can be spatially resolved but are not yet strongly affected by interaction with the surroundings. Our observations of SN 1987A with the Atacama Large Millimeter/submillimeter Array are of the highest resolution to date and reveal the detailed morphology of cold molecular gas in the innermost regions of the remnant. The 3D distributions of carbon and silicon monoxide (CO and SiO) emission differ, but both have a central deficit, or torus-like distribution, possibly a result of radioactive heating during the first weeks ("nickel heating"). The size scales of the clumpy distribution are compared quantitatively to models, demonstrating how progenitor and explosion physics can be constrained.
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| 49. |
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| 50. |
- Adiels, L., et al.
(författare)
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Investigations on baryonium and other rare pmacrp annihilation modes using high resolution pi0 spectrometers (PS 182)
- 1985
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Ingår i: Antiproton 1984. Proceedings of the VII European Symposium on Antiproton Interactions. - : Institution of Electrical Engineers (IEE). ; , s. 297-304
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Konferensbidrag (refereegranskat)abstract
- In the search for heavy, narrow exotic states such as baryonium or glueballs, carried out so far, various methods of high- and low-energy production, low-energy formation, and e+e- reactions were used. In particular, a search for baryonium states below threshold (mxlsimmppmacr) has shown some evidence [Richter et al., 1983, Brando et al., 1984] for a few states. However, the results of these measurements suffer from poor statistics. Among the possible methods which can be applied in the baryonium bound state research at LEAR, the authors consider the study of the reaction ppmacrrarrX+pi0 as the most promising. They have performed an experiment to study this reaction by means of an experimental set-up especially tailored for measuring monoenergetic pi0,s, allowing for both angular distribution measurements and high-resolution spectroscopy. They report on the preliminary results from our actual measurements of the inclusive pi0 and eta spectra following the antiproton annihilation at rest.
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