| 1. |
- Acharya, B. S., et al.
(author)
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Introducing the CTA concept
- 2013
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In: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 43, s. 3-18
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Journal article (other academic/artistic)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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| 2. |
- Birkby, J. L., et al.
(author)
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WTS-2 b: a hot Jupiter orbiting near its tidal destruction radius around a K dwarf
- 2014
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 440:2, s. 1470-1489
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Journal article (peer-reviewed)abstract
- We report the discovery of WTS-2 b, an unusually close-in 1.02-d hot Jupiter (M-P = 1.12M(J), R-P = 1.30R(J)) orbiting a K2V star, which has a possible gravitationally bound M-dwarf companion at 0.6 arcsec separation contributing similar to 20 per cent of the total flux in the observed J-band light curve. The planet is only 1.5 times the separation from its host star at which it would be destroyed by Roche lobe overflow, and has a predicted remaining lifetime of just similar to 40 Myr, assuming a tidal dissipation quality factor of Q(*)' = 10(6).Q(*)' is a key factor in determining how frictional processes within a host star affect the orbital evolution of its companion giant planets, but it is currently poorly constrained by observations. We calculate that the orbital decay of WTS-2 b would correspond to a shift in its transit arrival time of T-shift similar to 17 s after 15 yr assuming Q(*)' = 10(6). A shift less than this would place a direct observational constraint on the lower limit of Q(*)' in this system. We also report a correction to the previously published expected T-shift for WASP-18 b, finding that T-shift = 356 s after 10 yr for Q(*)' = 10(6), which is much larger than the estimated 28 s quoted in WASP-18 b discovery paper. We attempted to constrain Q(*)' via a study of the entire population of known transiting hot Jupiters, but our results were inconclusive, requiring a more detailed treatment of transit survey sensitivities at long periods. We conclude that the most informative and straightforward constraints on Q(*)' will be obtained by direct observational measurements of the shift in transit arrival times in individual hot Jupiter systems. We show that this is achievable across the mass spectrum of exoplanet host stars within a decade, and will directly probe the effects of stellar interior structure on tidal dissipation.
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| 3. |
- Graeger, R., et al.
(author)
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Experimental Study of the 238U(36S,3-5n)269-271Hs Reaction Leading to the Observation of 270Hs
- 2010
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In: Physical Review C (Nuclear Physics). - 0556-2813. ; 81:6
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Journal article (peer-reviewed)abstract
- The deformed doubly magic nucleus (270)Hs has so far only been observed as the four-neutron (4n) evaporation residue of the reaction Mg-26+Cm-248, where a maximum cross section of 3 pb was measured. Theoretical studies on the formation of (270)Hs in the 4n evaporation channel of fusion reactions with different entrance channel asymmetry in the framework of a two-parameter Smoluchowski equation predict that the reactions Ca-48+Ra-226 and S-36+U-238 result in higher cross sections due to lower reaction Q values, in contrast to simple arguments based on the reaction asymmetry, which predict opposite trends. Calculations using HIVAP predict cross sections for the reaction S-36+U-238 that are similar to those of the Mg-26+Cm-248 reaction. Here, we report on the first measurement of evaporation residues formed in the complete nuclear fusion reaction S-36+U-238 and the observation of (270)Hs, which is produced in the 4n evaporation channel, with a measured cross section of 0.8(-0.7)(+2.6) pb at 51-MeV excitation energy. The one-event cross-section limits (68% confidence level) for the 3n, 4n, and 5n evaporation channels at 39-MeV excitation energy are 2.9 pb, while the cross-section limits of the 3n and 5n channel at 51 MeV are 1.5 pb. This is significantly lower than the 5n cross section of the Mg-26+Cm-248 reaction at similar excitation energy.
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| 4. |
- Skorodko, T., et al.
(author)
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THE pp -> pp pi(0)pi(0) REACTION AND ITS LIMITING CASE, FUSION TO QUASI-BOUND He-2, IN SEARCH OF THE ABC EFFECT
- 2011
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In: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 702-704
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Journal article (peer-reviewed)abstract
- The pi(0)pi(0) production in pp-collisions has been investigated in exclusive and kinematically complete measurements from threshold up to T-p = 1.4 GeV. For incident energies T-p > 1 GeV, i.e. in the region beyond the Roper excitation, the Delta Delta excitation process takes over. The data are well explained by the t-channel Delta Delta process dominated by pion exchange. There is no low-mass enhancement (ABC effect) in the pi(0)pi(0)-invariant mass distribution beyond that given by the conventional t-channel Delta Delta process. This is also true for the limiting case, where the protons are in the quasi-bound He-2 state.
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| 5. |
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| 6. |
- Severo, J. H. F., et al.
(author)
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Error analysis in the electron temperature measurements in TCABR
- 2012
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In: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 370:1, s. 012045-
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Journal article (peer-reviewed)abstract
- An analytical method is proposed to evaluate the experimental uncertainty in the electron temperature measurements in the TCABR tokamak. Solving the integral equation resulting from the convolution of two functions, one representing, the scattered light and the other the spectral apparatus function, i.e., the polychromator, an analytical expression for the electron temperature is obtained, from which the uncertainty in the measured value is readily evaluated. The results show that the major contribution to the error comes from the noise in the signal; the uncertainties in the filters parameters do not contribute significantly to the total error.
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| 7. |
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