1,264 research outputs found
Oriented polar molecules in a solid inert-gas matrix: a proposed method for measuring the electric dipole moment of the electron
We propose a very sensitive method for measuring the electric dipole moment
of the electron using polar molecules embedded in a cryogenic solid matrix of
inert-gas atoms. The polar molecules can be oriented in the
direction by an applied electric field, as has recently been demonstrated by
Park, et al. [Angewandte Chemie {\bf 129}, 1066 (2017)]. The trapped molecules
are prepared into a state which has its electron spin perpendicular to
, and a magnetic field along causes precession of
this spin. An electron electric dipole moment would affect this
precession due to the up to 100~GV/cm effective electric field produced by the
polar molecule. The large number of polar molecules that can be embedded in a
matrix, along with the expected long coherence times for the precession, allows
for the possibility of measuring to an accuracy that surpasses current
measurements by many orders of magnitude. Because the matrix can inhibit
molecular rotations and lock the orientation of the polar molecules, it may not
be necessary to have an electric field present during the precession. The
proposed technique can be applied using a variety of polar molecules and inert
gases, which, along with other experimental variables, should allow for careful
study of systematic uncertainties in the measurement
Observing pulsars and fast transients with LOFAR
Low frequency radio waves, while challenging to observe,are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in the lowest 4 octaves of the ionospheric âradio windowâ: 10â240 MHz, that will greatly facilitate observing pulsars at low radio frequencies. Through the huge collecting area, long baselines, and flexible digital hardware, it is expected that LOFAR will revolutionize radio astronomy at the lowest frequencies visible from Earth.LOFAR is a next-generation radio telescope and a pathfinder to the Square Kilometre Array (SKA), in that it incorporates advanced multi-beaming techniques between thousands of individual elements. We discuss the motivation for low-frequency pulsar observations in general and the potential of LOFAR in addressing these science goals.We present LOFAR as it is designed to perform high-time-resolution observations of pulsars and other fast transients, and outline the various relevant observing modes and data reduction pipelines that are already or will soon be implemented to facilitate these observations. A number of results obtained from commissioning observations are presented to demonstrate the exciting potential of the telescope. This paper outlines the case for low frequency pulsar observations and is also intended to serve as a reference for upcoming pulsar/fast transient science papers with LOFAR
A Strong Upper Limit on the Pulsed Radio Luminosity of the Compact Object 1RXS J141256.0+792204
The ROSAT X-ray source 1RXS J141256.0+792204 has recently been identified as
a likely compact object whose properties suggest it could be a very nearby
radio millisecond pulsar at d = 80 - 260pc. We investigated this hypothesis by
searching for radio pulsations using the Westerbork Synthesis Radio Telescope.
We observed 1RXS J141256.0+792204 at 385 and 1380MHz, recording at high time
and frequency resolution in order to maintain sensitivity to millisecond
pulsations. These data were searched both for dispersed single pulses and using
Fourier techniques sensitive to constant and orbitally modulated periodicities.
No radio pulsations were detected in these observations, resulting in pulsed
radio luminosity limits of L_400 ~ 0.3 (d/250pc)^2 mJy kpc^2 and L_1400 ~ 0.03
(d/250pc)^2 mJy kpc^2 at 400 and 1400MHz respectively. The lack of detectable
radio pulsations from 1RXS J141256.0+792204 brings into question its
identification as a nearby radio pulsar, though, because the pulsar could be
beamed away from us, this hypothesis cannot be strictly ruled out.Comment: To appear in A&A. 3 page
Deflection of barium monofluoride molecules using the bichromatic force: A density-matrix simulation
A full density-matrix simulation is performed for optical deflection of a
barium monofluoride (BaF) beam using the bichromatic force,
which employs pairs of counter-propagating laser beams that are offset in
frequency. We show that the force is sufficient to separate BaF molecules from
the other products generated in a helium-buffer-gas-cooled ablation source. For
our simulations, the density-matrix and force equations are numerically
integrated during the entire time that the molecules pass through a laser beam
to ensure that effects of the evolution of the Doppler shift and of the optical
intensity and phase at the position of the molecule are properly included. The
results of this work are compared to those of a deflection scheme (Phys. Rev. A
107, 032811 (2023)) which uses pulses to drive frequency-resolved
transitions. This work is part of an effort by the EDM collaboration to
measure the electric dipole moment of the electron using BaF molecules embedded
in a cryogenic argon solid. Separation of BaF molecules will aid in producing a
sufficiently pure solid.Comment: 8 pages, 5 figure
Very hard states in neutron star low-mass X-ray binaries
We report on unusually very hard spectral states in three confirmed
neutron-star low-mass X-ray binaries (1RXS J180408.9-342058, EXO 1745-248, and
IGR J18245-2452) at a luminosity between ~ 10^{36-37} erg s^{-1}. When fitting
the Swift X-ray spectra (0.5 - 10 keV) in those states with an absorbed
power-law model, we found photon indices of \Gamma ~ 1, significantly lower
than the \Gamma = 1.5 - 2.0 typically seen when such systems are in their so
called hard state. For individual sources very hard spectra were already
previously identified but here we show for the first time that likely our
sources were in a distinct spectral state (i.e., different from the hard state)
when they exhibited such very hard spectra. It is unclear how such very hard
spectra can be formed; if the emission mechanism is similar to that operating
in their hard states (i.e., up-scattering of soft photons due to hot electrons)
then the electrons should have higher temperatures or a higher optical depth in
the very hard state compared to those observed in the hard state. By using our
obtained \Gamma as a tracer for the spectral evolution with luminosity, we have
compared our results with those obtained by Wijnands et al. (2015). We confirm
their general results in that also our sample of sources follow the same track
as the other neutron star systems, although we do not find that the accreting
millisecond pulsars are systematically harder than the non-pulsating systems.Comment: Accepted for publication in MNRA
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