521,829 research outputs found
Coherent Destruction of Photon Emission from a Single Molecule Source
The behavior of a single molecule driven simultaneously by a laser and by an
electric radio frequency field is investigated using a non-Hermitian
Hamiltonian approach. Employing the renormalization group method for
differential equations we calculate the average waiting time for the first
photon emission event to occur, and determine the conditions for the
suppression and enhancement of photon emission. An abrupt transition from
localization-like behavior to delocalization behavior is found.Comment: 5 pages, 4 figure
Identification of a Likely Radio Counterpart of the Rapid Burster
We have identified a likely radio counterpart to the low-mass X-ray binary
MXB 1730-335 (the Rapid Burster). The counterpart has shown 8.4 GHz radio
on/off behavior correlated with the X-ray on/off behavior as observed by the
RXTE/ASM during six VLA observations. The probability of an unrelated, randomly
varying background source duplicating this behavior is 1-3% depending on the
correlation time scale. The location of the radio source is RA 17h 33m 24.61s;
Dec -33d 23' 19.8" (J2000), +/- 0.1". We do not detect 8.4 GHz radio emission
coincident with type II (accretion-driven) X-ray bursts. The ratio of radio to
X-ray emission during such bursts is constrained to be below the ratio observed
during X-ray persistent emission at the 2.9-sigma level. Synchrotron bubble
models of the radio emission can provide a reasonable fit to the full data set,
collected over several outbursts, assuming that the radio evolution is the same
from outburst to outburst, but given the physical constraints the emission is
more likely to be due to ~hour-long radio flares such as have been observed
from the X-ray binary GRS 1915+105.Comment: 28 pages, 4 figures; accepted for publication in ApJ (no changes
Evidence of an Internal Dissipation Origin for the High-energy Prompt Emission of GRB 170214A
The origin of the prompt high-energy (MeV) emission of Gamma-ray Bursts
(GRBs), detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray
Space Telescope, is still under debate, for which both the external shock
origin and internal dissipation origin have been suggested. In the internal
dissipation scenario, the high energy emission is expected to exhibit
significant temporal variability, tracking the keV/MeV fast variable behavior.
Here, we report a detailed analysis on the Fermi data of GRB~170214A, which is
sufficiently bright in the high energy to enable a quantitative analysis of the
correlation between high-energy emission and keV/MeV emission with high
statistics. Our result shows a clear temporal correlation between high-energy
and keV/MeV emission in the whole prompt emission phase as well as in two
decomposed short time intervals. Such correlation behavior is also found in
some other bright LAT GRBs, i.e., GRB 080916C, 090902B and 090926A. For these
GRBs as well as GRB 090510, we also find the rapid temporal variability in the
high-energy emission. We thus conclude that the prompt high-energy emission in
these bright LAT GRBs should be due to internal origin.Comment: 12 pages, 4 figures, Accepted for publication in Ap
Witnessing the gradual slow-down of powerful extragalactic jets: The X-ray -- optical -- radio connection
A puzzling feature of the {\it Chandra}--detected quasar jets is that their
X-ray emission decreases faster along the jet than their radio emission,
resulting to an outward increasing radio to X-ray ratio. In some sources this
behavior is so extreme that the radio emission peak is located clearly
downstream of that of the X-rays. This is a rather unanticipated behavior given
that the inverse
Compton nature of the X-rays and the synchrotron radio emission are
attributed to roughly the same electrons of the jet's non-thermal electron
distribution. In this note we show that this morphological behavior can result
from the gradual deceleration of a relativistic flow and that the offsets in
peak emission at different wavelengths carry the imprint of this deceleration.
This notion is consistent with another recent finding, namely that the jets
feeding the terminal hot spots of powerful radio galaxies and quasars are still
relativistic with Lorentz factors . The picture of the
kinematics of powerful jets emerging from these considerations is that they
remain relativistic as they gradually decelerate from Kpc scales to the hot
spots, where, in a final collision with the intergalactic medium, they
slow-down rapidly to the subrelativistic velocities of the hot spot advance
speed.Comment: Submitted in ApJ Letters on Jan. 14, 200
Non-Markovian quantum trajectories for spectral detection
We present a formulation of non-Markovian quantum trajectories for open
systems from a measurement theory perspective. In our treatment there are three
distinct ways in which non-Markovian behavior can arise; a mode dependent
coupling between bath (reservoir) and system, a dispersive bath, and by
spectral detection of the output into the bath. In the first two cases the
non-Markovian behavior is intrinsic to the interaction, in the third case the
non-Markovian behavior arises from the method of detection. We focus in detail
on the trajectories which simulate real-time spectral detection of the light
emitted from a localized system. In this case, the non-Markovian behavior
arises from the uncertainty in the time of emission of particles that are later
detected. The results of computer simulations of the spectral detection of the
spontaneous emission from a strongly driven two-level atom are presented
ORFEUS II and IUE Spectroscopy of EX Hydrae
Using ORFEUS-SPAS II FUV spectra, IUE UV spectra, and archival EUVE deep
survey photometry, we present a detailed picture of the behavior of the
magnetic cataclysmic variable EX Hydrae. Like HUT spectra of this source, the
FUV and UV spectra reveal broad emission lines of He II, C II-IV, N III and V,
O VI, Si III-IV, and Al III superposed on a continuum which is blue in the UV
and nearly flat in the FUV. Like ORFEUS spectra of AM Her, the O VI doublet is
resolved into broad and narrow emission components. Consistent with its
behavior in the optical, the FUV and UV continuum flux densities, the FUV and
UV broad emission line fluxes, and the radial velocity of the O VI broad
emission component all vary on the spin phase of the white dwarf, with the
maximum of the FUV and UV continuum and broad emission line flux light curves
coincident with maximum blueshift of the broad O VI emission component. On the
binary phase, the broad dip in the EUV light curve is accompanied by strong
eclipses of the UV emission lines and by variations in both the flux and radial
velocity of the O VI narrow emission component. The available data are
consistent with the accretion funnel being the source of the FUV and UV
continuum and the O VI broad emission component, and the white dwarf being the
source of the O VI narrow emission component.Comment: 21 pages, 10 Postscript figures; LaTeX format, uses aaspp4.sty;
table2.tex included separately because it must be printed sideways - see
instructions in the file; accepted on 1999 Feb 20 for publication in The
Astrophysical Journa
Method to obtain nonuniformity information from field emission behavior
Copyright © 2010 American Vacuum Society / American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Vacuum Science and Technology Part B: Microelectronics and Nanometer Structures, 28(3), Article number 441 and may be found at http://scitation.aip.org/content/avs/journal/jvstb/28/3/10.1116/1.3327928.This article describes the characterization of field emission from a planar cathode to a spherical anode with the approach curve method (ACM). In such a diode configuration the electric field strength at the cathode surface is nonuniform. This nonuniformity gives an extra degree of freedom and it allows the interpretation of the current-voltage and voltage-distance (V×d) curves in terms of nonuniformity. The authors apply the ACM to Cu emitters to explain the nonlinearity of the V×d curve in ACM measurements. This analysis provides a good insight into field emission phenomena, supporting a method for nonuniformity characterization based on field emission behavior
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