5,090 research outputs found
The Ulysses Supplement to the BATSE 4Br Catalog of Cosmic Gamma-Ray Bursts
We present Interplanetary Network localization information for 147 gamma-ray
bursts observed by the Burst and Transient Source Experiment between the end of
the 3rd BATSE catalog and the end of the 4th BATSE catalog, obtained by
analyzing the arrival times of these bursts at the Ulysses and Compton
Gamma-Ray Observatory (CGRO) spacecraft. For any given burst observed by these
two spacecraft, arrival time analysis (or "triangulation") results in an
annulus of possible arrival directions whose half-width varies between 7
arcseconds and 2.3 degrees, depending on the intensity and time history of the
burst, and the distance of the Ulysses spacecraft from Earth. This annulus
generally intersects the BATSE error circle, resulting in an average reduction
of the error box area of a factor of 25.Comment: Accepted for publication in the Astrophysical Journal Supplemen
The protein import apparatus of chloroplasts
Routing of cytosolically synthesized precursor proteins into chloroplasts is a specific process which involves a multitude of soluble and membrane components. In this review we wil1 focus on early events of the translocation pathway of nuclear coded plastidic precursor proteins and compare import routes for polypeptide of the outer chloroplast envelope to that of internal chloroplast compartments. A number of proteins housed in the chloroplast envelopes have been implied to be involved in the translocation process, but so far a certain function has not been assigned to any of these proteins. The only exception could be an envelope localized hsc 70 homologue which could retain the import competence of a precursor protein in transit into the organelle
No Evidence for Gamma-Ray Burst/Abell Cluster or Gamma- Ray Burst/Radio-Quiet Quasar Correlations
We examine the recent claims that cosmic gamma-ray bursts are associated with
either radio-quiet quasars or Abell clusters. These associations were based on
positional coincidences between cataloged quasars or Abell clusters, and
selected events from the BATSE 3B catalog of gamma-ray bursts. We use a larger
sample of gamma-ray bursts with more accurate positions, obtained by the 3rd
Interplanetary Network, to re-evaluate these possible associations. We find no
evidence for either.Comment: Accepted for publication in the Astrophysical Journa
Mixing-induced CP violating sources for electroweak baryogenesis from a semiclassical approach
The effects of flavor mixing in electroweak baryogenesis is investigated in a
generalized semiclassical WKB approach. Through calculating the nonadiabatic
corrections to the particle currents it is shown that extra CP violation
sources arise from the off-diagonal part of the equation of motion of particles
moving inside the bubble wall. This type of mixing-induced source is of the
first order in derivative expansion of the Higgs condensate, but is oscillation
suppressed. The numerical importance of the mixing-induced source is discussed
in the Minimal Supersymmetric Standard Model and compared with the source term
induced by semiclassical force. It is found that in a large parameter space
where oscillation suppression is not strong enough, the mixing-induced source
can dominate over that from the semiclassical force.Comment: 19 pp, 2 figs, 1 table, some comments added, to appear in
Eur.Phys.J.
The Ulysses Supplement to the BATSE 3B Catalog of Cosmic Gamma-Ray Bursts
We present Interplanetary Network localization information for 218 gamma-ray
bursts in the 3rd BATSE catalog, obtained by analyzing the arrival times of
these bursts at the Ulysses and Compton Gamma-Ray Observatory (CGRO)
spacecraft. For any given burst observed by these two spacecraft, arrival time
analysis (or "triangulation") results in an annulus of possible arrival
directions whose half-width varies between 7 arcseconds and 32 arcminutes,
depending on the intensity and time history of the burst, and the distance of
the Ulysses spacecraft from Earth. This annulus generally intersects the BATSE
error circle, resulting in an average reduction of the error box area of a
factor of 30.Comment: Accepted for publication in the Astrophysical Journal Supplemen
A giant, periodic flare from the soft gamma repeater SGR1900+14
Soft gamma repeaters are high-energy transient sources associated with
neutron stars in young supernova remnants. They emit sporadic, short (~ 0.1 s)
bursts with soft energy spectra during periods of intense activity. The event
of March 5, 1979 was the most intense and the only clearly periodic one to
date. Here we report on an even more intense burst on August 27, 1998, from a
different soft gamma repeater, which displayed a hard energy spectrum at its
peak, and was followed by a ~300 s long tail with a soft energy spectrum and a
dramatic 5.16 s period. Its peak and time integrated energy fluxes at Earth are
the largest yet observed from any cosmic source. This event was probably
initiated by a massive disruption of the neutron star crust, followed by an
outflow of energetic particles rotating with the period of the star. Comparison
of these two bursts supports the idea that magnetic energy plays an important
role, and that such giant flares, while rare, are not unique, and may occur at
any time in the neutron star's activity cycle.Comment: Accepted for publication in Natur
Can multistate dark matter annihilation explain the high-energy cosmic ray lepton anomalies?
Multistate dark matter (DM) models with small mass splittings and couplings
to light hidden sector bosons have been proposed as an explanation for the
PAMELA/Fermi/H.E.S.S. high-energy lepton excesses. We investigate this proposal
over a wide range of DM density profiles, in the framework of concrete models
with doublet or triplet dark matter and a hidden SU(2) gauge sector that mixes
with standard model hypercharge. The gauge coupling is bounded from below by
the DM relic density, and the Sommerfeld enhancement factor is explicitly
computable for given values of the DM and gauge boson masses M, mu and the
(largest) dark matter mass splitting delta M_{12}. Sommerfeld enhancement is
stronger at the galactic center than near the Sun because of the radial
dependence of the DM velocity profile, which strengthens the inverse Compton
(IC) gamma ray constraints relative to usual assumptions. We find that the
PAMELA/Fermi/H.E.S.S. lepton excesses are marginally compatible with the model
predictions, and with CMB and Fermi gamma ray constraints, for M ~ 800 GeV, mu
~ 200 MeV, and a dark matter profile with noncuspy Einasto parameters alpha >
0.20, r_s ~ 30 kpc. We also find that the annihilating DM must provide only a
subdominant (< 0.4) component of the total DM mass density, since otherwise the
boost factor due to Sommerfeld enhancement is too large.Comment: 20 pages, 12 figures; v2: Corrected branching ratio for ground state
DM annihilations into leptons, leading to boost factors that are larger than
allowed. Added explicit results for doublet DM model. Some conclusions
changed; main conclusion of tension between inverse Compton constraints and
N-body simulations of halo profiles is unchange
Where is SGR1806-20?
We apply a statistical method to derive very precise locations for soft gamma
repeaters using data from the interplanetary network. We demonstrate the
validity of the method by deriving a 600 arcsec^2 error ellipse for SGR1900+14
whose center agrees well with the VLA source position. We then apply it to
SGR1806-20, for which we obtain a 230 arcsec^2 error ellipse, the smallest
burst error box to date. We find that the most likely position of the source
has a small but significant displacement from that of the non-thermal core of
the radio supernova remnant G10.0-0.3, which was previously thought to be the
position of the repeater. We propose a different model to explain the changing
supernova remnant morphology and the positions of the luminous blue variable
and the bursting source.Comment: 12 pages and 2 color figures, accepted for publication in
Astrophysical Journal Letter
Reactivation and Precise IPN Localization of the Soft Gamma Repeater SGR1900+14
In 1998 May, the soft gamma repeater SGR1900+14 emerged from several years of
quiescence and emitted a series of intense bursts, one with a time history
unlike any previously observed from this source. Triangulation using Ulysses,
BATSE, and KONUS data give a 1.6 square arcminute error box near the galactic
supernova remnant G42.8+0.6. This error box contains a quiescent soft X-ray
source which is probably a neutron star associated with the soft repeater.Comment: Accepted for publication in the Astrophysical Journal Letter
Adenylate effects on protein phosphorylation in the interenvelope lumen of pea chloroplasts
A 64-kilodalton (kDa) protein, situated in the lumen between the inner and outer envelopes of pea (Pisum sativum L.) chloroplasts (Soll and Bennett 1988, Eur. J. Biochem., 175, 301â307) is shown to undergo reversible phosphorylation in isolated mixed envelope vesicles. It is the most conspicuously labelled protein after incubation of envelopes with 33 nmol·1-1 [-32P]ATP whereas incubation with 50 mol·1-1 [-32P]ATP labels most prominently two outer envelope proteins (86 and 23 kDa). Half-maximum velocity for phosphorylation of the 64-kDa protein occurs with 200 nmol·1-1 ATP, and around 40 mol·1-1 ATP for phosphorylation of the 86- and 23-kDa proteins, indicating the operation of two distinct kinases. GGuanosine-, uridine-, cytidine 5-triphosphate and AMP are poor inhibitors of the labelling of the 64-kDa protein with [-32P]ATP. On the other hand, ADP has a potent influence on the extent of labelling (half-maximal inhibition at 1â5 mol·1-1). The ADP-dependent appearance of 32P in ATP indicates that ADP acts by reversal of kinase activity and not as a competitive inhibitor. However, the most rapid loss of 32P from pre-labelled 64-kDa protein occurs when envelope vesicles are incubated with ATP t1/2=15 s at 20 molsd1-1 ATP). This induced turnover of phosphate appears to be responsible for the rapid phosphoryl turnover seen in situ
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