123291324
Nuclear charge and magnetization density distribution parameters from elastic electron scattering
A compilation of nuclear charge- and magnetization-density-distribution parameters, found from elastic electron scattering, is presented. The data on charge distributions, obtained on the basis of a phenomenological model, are given in three separate tables: parameters of nuclei, differences therein between isotopes and between other neighbouring nuclei such as isotones. A fourth table is devoted to charge distributions obtained by model-independent analyses. In the final table the available data on magnetization-density distributions are listed. References through April 1974 have been covered.
211546584
A Compton Backscattering Polarimeter for Electron Beams below 1 GeV
A recently installed polarized electron source will allow internal target experiments to be performed with polarized electrons at the NIKHEF Internal Target Hall, lb measure the longitudinal component of the polarization vector of the stored electron beam, a Polarimeter based on spin-dependent Compton scattering has been developed and successfully commissioned.
123075042
The polarized electron source at NIKHEF
An overview of the polarized electron source used at the NIKHEF accelerator facility is given. Since its first operation in September 1996 we have obtained currents in the source larger than 150 mA, and polarization degrees up to 88%. Approximately 350 hours have been dedicated to physics with a polarized 3He internal target. Using one InGaAsP photocathode, 2 μs long pulses were produced with a current of 2 mA in the local linac, with a polarization degree of 82.5%, at a repetition rate of 1 Hz. Source operations had to be interrupted about every eleventh day for approximately an hour for photocathode reactivation. A photocathode lifetime (1/e) of 180 hours has been achieved.
8150339
Core polarization and quenching in stretched spin states: Case study of the 9- Ex=3.522 MeV state in 116Sn.
125342954
A Compton backscattering polarimeter for measuring longitudinal electron polarization
Compton backscattering polarimetry provides a fast measurement of the polarization of an electron beam in a storage ring. Since the method is nondestructive, the polarization of the electrons can be monitored during internal target experiments. At NIKHEF a Compton polarimeter has been constructed to measure the polarization of the longitudinally polarized electrons stored in the AmPS ring. First results obtained with the polarimeter, the first Compton polarimeter to measure the polarization of a stored longitudinally polarized electron beam, are presented in this paper.
123449211
A Pair Polarimeter for Linearly Polarized High Energy Photons
A high quality beam of linearly polarized photons of several GeV will become available with the coherent bremsstrahlung technique at JLab. We have developed a polarimeter which requires about two meters of the beam line, has an analyzing power of 20% and an efficiency of 0.02%. The layout and first results of a polarimeter test on the laser back-scattering photon beam at SPring-8/LEPS are presented.
7875116
The Millennium Outburst of the Cool Hypergiant Rho Cassiopeiae: Spectroscopy and Modeling
Between 2000 June and September an exceptional variability phase occurred in the peculiar F-type hypergiant Rho Cas, when the V-brightness dimmed by at least a full magnitude. The star recovered from this deep minimum by 2001 April. It is the third outburst of Rho Cas on record in the last century. We observe TiO absorption bands in high-resolution optical and near-IR spectra obtained with the Utrecht Echelle Spectrograph during the summer of 2000. TiO formation in the outer atmosphere occurred before the deep brightness minimum.Atmospheric models reveal that the effective temperature decreases by at least 3000 K, and the TiO shell is driven supersonically with Mdot =~5.4 10^-2 Msun/yr. Strong episodic mass loss and TiO have also been observed during the outbursts of 1945-47 and 1985-86. An analysis of the exceptional outburst spectra of 2000-01 is provided, by comparing with high-resolution optical spectra of the early M-type supergiants Mu Cep (Ia) and Betelgeuse (Iab). During the outburst, central emission appears above the local continuum level in the split Na D lines. The outburst spectra indicate the formation of a low- temperature, optically thick circumstellar gas shell of 3 10^-2 Msun during \~200 d, caused by dynamic instability of the upper atmosphere of this pulsating massive supergiant near the Eddington luminosity limit. We present an equation that correctly predicts the outburst time-scale, whereby the shell ejection is driven by the release of hydrogen recombination energy. We observe that the mass-loss rate during the outburst is of the same order of magnitude as has been proposed for the outbursts of Eta Carinae. The research results in this paper are described in further detail in Lobel et al. (2003). A spectral movie sequence of the outburst is available at this http URL
15595029
Rapid variations of narrow absorption line components in the spectrum of P Cygni
Abstract We report the detection of rapid wavelength and intensity variations of narrow components in absorption line profiles of the hot galactic supergiant P Cygni . During most of the time, in 1 week of observations, there were two such components present. Although the period of observation is too short for firm conclusions, the velocity curves do not contradict the photometric period of 17.3 days. These curves may be interpreted as a double wave, ‘swinging in counterphase’. This observation would suggest the presence of one long wave over the stellar surface. The waves are possibly gravity waves with wavelengths of the order of half the stellar radius.
18587770
High-Resolution Spectroscopy of the Yellow Hypergiant ρ Cassiopeiae from 1993 through the Outburst of 2000-2001
We present an overview of the spectral variability of the peculiar F-type hypergiant ρ Cas, obtained from our long-term monitoring campaigns over the past 8.5 yr with four spectrographs in the northern hemisphere. Between 2000 June and September an exceptional variability phase occurred when the V brightness dimmed by about a full magnitude. The star recovered from this deep minimum by 2001 April. It is the third outburst of ρ Cas on record in the last century. We observe TiO absorption bands in high-resolution near-IR spectra obtained with the Utrecht Echelle Spectrograph during the summer of 2000. TiO formation in the outer atmosphere occurred before the deep brightness minimum. Atmospheric models reveal that the effective temperature decreases by at least 3000 K, and the TiO shell is driven supersonically with 5.4 × 10-2 M☉ yr-1. Strong episodic mass loss and TiO have also been observed during the outbursts of 1945-1947 and 1985-1986. A detailed analysis of the exceptional outburst spectra is provided, by comparing with high-resolution optical spectra of the early M-type supergiants μ Cep (Ia) and Betelgeuse (Iab). During the outburst, central emission appears above the local continuum level in the split Na D lines. A prominent optical emission line spectrum appears in variability phases of fast wind expansion. The radial velocity curves of Hα and of photospheric metal absorption lines signal a very extended and velocity-stratified dynamic atmosphere. The outburst spectra indicate the formation of a low-temperature, optically thick circumstellar gas shell of 3 × 10-2 M☉ during 200 days, caused by dynamic instability of the upper atmosphere of this pulsating massive supergiant near the Eddington luminosity limit. We observe that the mass-loss rate during the outburst is of the same order of magnitude as has been proposed for the outbursts of η Carinae. We present calculations that correctly predict the outburst timescale, whereby the shell ejection is driven by the release of hydrogen ionization recombination energy.
118228975
Mass loss rates in the Hertzsprung-Russell diagram
Discussion des donnees de la litterature concernant les pertes de masse de 271 etoiles de types O o M de population I, etablissement d'une relation M˙(T eff , L/L ○. ) representant la perte de masse-M˙ comme fonction de la temperature effective et de la luminosite et discussion de la precision de la procedure d'ajustement
117810362
TeV Gamma-Ray Observations of the Cataclysmic Variable AE Aqr