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Träfflista för sökning "WFRF:(Perez A. D.) srt2:(1995-1999)"

Sökning: WFRF:(Perez A. D.) > (1995-1999)

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1.
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2.
  • Edelson, R. A., et al. (författare)
  • Multiwavelength observations of short-timescale variability in NGC 4151. IV. Analysis of multiwavelength continuum variability
  • 1996
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 364-377377
  • Tidskriftsartikel (refereegranskat)abstract
    • For pt.III see ibid., vol.470, no.1, p.349-63 (1996). Combines data from the three preceding papers in order to analyze the multi wave-band variability and spectral energy distribution of the Seyfert 1 galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in medium-energy (~1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA=6%) variations (uncorrelated with those at lower energies) were seen at soft gamma-ray energies of ~100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime, the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 Aring. These data do not probe extreme ultraviolet (1200 Aring to 0.1 keV) or hard X-ray (250 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of lsim0.15 day between 1275 Aring and the other ultraviolet bands, lsim0.3 day between 1275 Aring and 1.5 keV, and lsim1 day between 1275 and 5125 Aring. These tight limits represent more than an order of magnitude improvement over those determined in previous multi-wave-band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (ales-2.5)
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3.
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4.
  • Crenshaw, D. M., et al. (författare)
  • Multiwavelength observations of short-timescale variability in NGC 4151. I. Ultraviolet observations
  • 1996
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 322-335335
  • Tidskriftsartikel (refereegranskat)abstract
    • Presents the results of an intensive ultraviolet monitoring campaign on the Seyfert 1 galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously with the International Ultraviolet Explorer for 9.3 days, yielding a pair of LWP and SWP spectra every ~70 minutes, and during 4 hr periods for 4 days prior to and 5 days after the continuous-monitoring period. The sampling frequency of the observations is an order of magnitude higher than that of any previous UV monitoring campaign on a Seyfert galaxy. The continuum fluxes in bands from 1275 to 2688 Aring went through four significant and well-defined ldquoeventsrdquo of duration 2-3 days during the continuous-monitoring period. The authors find that the amplitudes of the continuum variations decrease with increasing wavelength, which extends a general trend for this and other Seyfert galaxies to smaller timescales (i.e., a few days). The continuum variations in all the UV bands are simultaneous to within an accuracy of ~0.15 days, providing a strict constraint on continuum models. The emission-line light curves show only one major event during the continuous monitoring (a slow rise followed by a shallow dip) and do not correlate well with continuum light curves over the short duration of the campaign, because the timescale for continuum variations is apparently smaller than the response times of the emission lines
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5.
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6.
  • Andres, E., et al. (författare)
  • AMANDA : Status, results and future
  • 1999
  • Ingår i: Proceedings, 8th International Workshop, Venice, Italy, February 23-26, 1999. Vol. 1, 2. ; , s. 63-79
  • Konferensbidrag (refereegranskat)abstract
    • We review the status of the AMANDA neutrino telescope. We present resultsobtained from the four-string prototype array AMANDA-B4 and describe themethods of track reconstruction and neutrino event separation. We give also firstresults of the analysis of the 10-string detector AMANDA-B10, in particular onatmospheric neutrinos and the search for magnetic monopoles. We sketch thefuture schedule on the way to a cube kilometer telescope at the South Pole,ICECUBE.
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7.
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8.
  • Andrés, E., et al. (författare)
  • Status of the AMANDA experiment
  • 1999
  • Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier. - 0920-5632 .- 1873-3832. ; 70:1-3, s. 448-452
  • Tidskriftsartikel (refereegranskat)abstract
    • The AMANDA high energy neutrino telescope has successfully been increased in size from four detector strings to ten detector strings during the 1996/1997 season. The first upward going muon-neutrino candidates have been reconstructed from the 1996 year's four-string data. Three new detector strings will be deployed during 1997/1998 to 2350 metres depth.
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9.
  • Wischnewski, R., et al. (författare)
  • The AMANDA neutrino detector
  • 1999
  • Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier. - 0920-5632 .- 1873-3832. ; 75:1-2, s. 412-414
  • Tidskriftsartikel (refereegranskat)abstract
    • The first stage of the AMANDA High Energy Neutrino Detector at the South Pole, the 302 PMT array AMANDA-B with an expected effective area for TeV neutrinos of ∼ 104 m2, has been taking data since 1997. Progress with calibration, investigation of ice properties, as well as muon and neutrino data analysis are described. The next stage 20-string detector AMANDA-II with ∼800 PMTs will be completed in spring 2000.
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10.
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11.
  • Kownacki, J, et al. (författare)
  • High-spin studies of the neutron deficient nuclei In-103, In-105, In-107, and In-109
  • 1997
  • Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 627:2, s. 239-258
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states of the isotopes 103,105,107,109In have been investigated using in-beam γ-ray spectroscopic methods. Results from three different experiments are presented. Targets of 54Fe, 50Cr, and 92Mo were bombarded by a 270 and 261 MeV 58Ni beam and by a 95 MeV 19F beam, respectively. Reaction channel separation was achieved with a charged-particle detector array and in the first two experiments also with a 1π neutron detector system. As a result of these experiments the level schemes of 103,105,107,109In were significantly extended. Excited states of these odd-A indium isotopes are discussed within the framework of the nuclear shell model and the hole-core coupling scheme. The systematics of excited states of light odd-A indium isotopes is also discussed.
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12.
  • Palacz, M, et al. (författare)
  • In beam gamma-ray spectroscopy of very neutron deficient odd-cadmium isotopes
  • 1997
  • Ingår i: Acta Physica Polonica B. - : ACTA PHYSICA POLONICA B, JAGELLONIAN UNIV, INST PHYSICS. - 0587-4254 .- 1509-5770. ; 28:1-2, s. 309-313
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in the very neutron deficient odd cadmium isotopes Cd-99, Cd-101 and Cd-103 are discussed in terms of the nuclear shell model. Systematics of excited states in Cd99-109 is presented.
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13.
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14.
  • Persson, J, et al. (författare)
  • In-beam gamma-ray spectroscopy of Cd-102
  • 1997
  • Ingår i: Nuclear Physics A. - : ELSEVIER SCIENCE BV. - 0375-9474 .- 1873-1554. ; 627:1, s. 101-118
  • Tidskriftsartikel (refereegranskat)abstract
    • Neutron deficient nuclei close to 100Sn have been studied using the NORDBALL Ge-detector array together with ancillary particle detectors. Evaporation residues from the compound nucleus 108Te were identified with charged particle and neutron detectors. In this paper a considerable extension of the level scheme of the nucleus 102Cd is presented. The strongest cascade of the new level scheme reveals an irregular sequence of dipole transitions above Iπ = 10+ extending up to spin 17. A strongly populated rather regular side band consisting of four quadrupole transitions ranging from spin 9 to spin 17 was also discovered. This band was tentatively assigned negative parity. Shell model calculations were performed and a very good agreement with the experimental results was found. The excited states could successfully be interpreted as neutron particle and proton hole excitations with respect to the doubly closed core 50100Sn50.
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15.
  • Persson, J, et al. (författare)
  • New spectroscopic data on Cd-102
  • 1996
  • Ingår i: Acta Physica Polonica B. - : POLISH ACAD SCIENCES INST PHYSICS. - 0587-4254 .- 1509-5770. ; 27:1-2, s. 171-178
  • Tidskriftsartikel (refereegranskat)abstract
    • Gamma ray spectroscopy of neutron deficient nuclei close to the doubly magic nucleus Sn-100 has been performed using a heavy-ion reaction and the NORDBALL Ge-detector array. Evaporation residues were identified by means of charged particle and neutron detection. Transitions in 31 different evaporation residues were identified. New results on Cd-102 are presented.
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16.
  • DOMBRADI, Z, et al. (författare)
  • HIGH-SPIN SPECTROSCOPY OF TE-109
  • 1995
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 51:5, s. 2394-2399
  • Tidskriftsartikel (refereegranskat)
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17.
  • Erkens, U., et al. (författare)
  • Monitoring of active galactic nuclei. VI. The quasar Mrk 876
  • 1995
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 296:1, s. 90-9898
  • Tidskriftsartikel (refereegranskat)abstract
    • For pt. V see ibid., vol. 285, no. 3, p. 857-67 (1994). We present the results of a 6 month monitoring campaign of Mrk 876, a low luminosity quasar with M absap-24. High resolution spectroscopy and direct imaging in the Johnson filters B, V, R, I was carried out in the first half of 1990. Line and continuum light curves are presented. Mrk 876 showed a decrease of 17% in the continuum over the whole observing period whereas the line flux of Hbeta and Halpha stayed constant. This implies, that the radius of the broad line region is larger than 6 light months. Coadded spectra of Hbeta and Halpha are presented which confirm an extreme asymmetry of the line profiles to the red. With respect to much earlier spectra the line profiles changed considerably
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18.
  • ERKENS, U, et al. (författare)
  • MONITORING OF ACTIVE GALACTIC NUCLEI .6. THE QUASAR MKN-876
  • 1995
  • Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 296:1, s. 90-98
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • We present the results of a 6 month monitoring campaign of Mkn 876, a low luminosity quasar with M(abs) approximate to -24. High resolution spectroscopy and direct imaging in the Johnson filters B, V, R, I was carried out in the first half of 1990. Line a
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19.
  • Koratkar, A, et al. (författare)
  • The disappearing broad absorption lines and variable emission lines in NGC 3516
  • 1996
  • Ingår i: ASTROPHYSICAL JOURNAL. - : UNIV CHICAGO PRESS. - 0004-637X. ; 470:1, s. 378-393
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The Seyfert 1 galaxy NGC 3516 was monitored during 1993 February 16-May 13 by IUE every 4 days for the first month, and then every 2 days for 2 months giving a total of 40 observations. This paper gives the initial results from this campaign, (1) The broa
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20.
  • Brown, D, et al. (författare)
  • Crustal-scale structure and evolution of an arc-continent collision zone in the southern Urals, Russia
  • 1998
  • Ingår i: Tectonics. - : American Geophysical Union (AGU). - 0278-7407 .- 1944-9194. ; 17:2, s. 158-171
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The outcropping geology of the southern Urals contains a well-preserved accretionary complex related to the Paleozoic collision that took place between the Magnitogorsk arc and the former East European Craton. The crustal-scale structure of the accretionary complex has been determined from outcropping field geology that is integrated with three reflection seismic profiles. The reflection profiles show the accretionary complex to be highly reflective, allowing direct comparison of many reflections with surface geological features. We interpret the accretionary complex to be a thrust stack that is composed of shallowly subducted continental shelf and rise material, syncollisional sediments derived from the arc, deeply subducted high-pressure gneisses that are intercalated with eclogites and blueschist, and, at the highest structural level, ophiolite complexes. It is bound at the base by a thrust and at the rear by a highly deformed zone (the Main Uralian fault) adjacent to the backstop (the Magnitogorsk arc). Deposition of the Late Devonian volcaniclastic sediments of the Zilair Formation appears to be related to collision, uplift, and erosion of the arc, possibly following the arrival of the full thickness of the East European Craton continental crust at the subduction zone. With the arrival of the continental crust at the subduction zone, offscraping and underplating of Paleozoic slope and platform material took place at the base of the accretionary complex. Uplift of the arc was followed by its collapse and the unconformable deposition of Lower Carboniferous shallow water carbonates on top of it. A time lag of 10 - 15 Myr occurred between the high-pressure metamorphism and the subsequent arrival of the East European Craton at the subduction zone.
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  • Resultat 1-20 av 20

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