950 research outputs found
INTEGRAL observations of PSR B0540-69
PSR B0540-69 is often called an extragalactic 'twin' of the Crab pulsar in
the Large Magellanic Cloud. The pulsar is embedded in a synchrotron nebula in
the center of SNR 0540-69.3. It was discovered with the Einstein satellite with
P~50 ms, spin-down age of ~1500 years and a spin-down luminosity of ~10^38
erg/s. It has since been detected with all major X-ray telescopes. At X-ray
energies up to ~40 keV the latest observations were reported from RXTE and from
INTEGRAL (only spectrum) in the context of a survey of the LMC. Optical pulsed
emission and faint radio emission have also been found from PSR B0540-69. The
INTEGRAL analysis presented here is based on observations of the LMC obtained
in Jan. 2003 and Jan. 2004 with a total exposure of ~1.5 Ms. In the mosaic maps
from the total exposure (JEM-X and IBIS/ISGRI) a source at the location of PSR
B0540-69 is clearly visible up to energies of ~200 keV. After barycentric
correction and determination of the pulsar phases, based on theephemeris
available from contemporaneous RXTE data, the lightcurves show the
characteristic shape of a broad pulse up into the 40-100 keV band. At higher
energies no significant pulsation is detectable. We derive the spectrum of the
total source from the ISGRI data. The photon spectrum can be fitted with a
power law of index 2.22, which is compatible with the result found by Goetz et
al., 2006.Comment: Proceedings of the 363. WE-Heraeus Seminar on: Neutron Stars and
Pulsars (Posters and contributed talks) Physikzentrum Bad Honnef, Germany,
May.14-19, 2006, eds. W.Becker, H.H.Huang, MPE Report 291, pp.44-5
Controlled Production of Sub-Radiant States of a Diatomic Molecule in an Optical Lattice
We report successful production of sub-radiant states of a two-atom system in
a three-dimensional optical lattice starting from doubly occupied sites in a
Mott insulator phase of a quantum gas of atomic ytterbium. We can selectively
produce either sub-radiant 1g state or super-radiant 0u state by choosing the
excitation laser frequency. The inherent weak excitation rate for the
sub-radiant 1g state is overcome by the increased atomic density due to the
tight-confinement in a three-dimensional optical lattice. Our experimental
measurements of binding energies, linewidth, and Zeeman shift confirm
observation of sub-radiant levels of the 1g state of the Yb_2 molecule.Comment: To be published in Phys. Rev. Let
Observations of X-rays and Thermal Dust Emission from the Supernova Remnant Kes 75
We present Spitzer Space Telescope and Chandra X-ray Observatory observations
of the composite Galactic supernova remnant Kes 75 (G29.7-0.3). We use the
detected flux at 24 microns and hot gas parameters from fitting spectra from
new, deep X-ray observations to constrain models of dust emission, obtaining a
dust-to-gas mass ratio M_dust/M_gas ~0.001. We find that a two-component
thermal model, nominally representing shocked swept-up interstellar or
circumstellar material and reverse-shocked ejecta, adequately fits the X-ray
spectrum, albeit with somewhat high implied densities for both components. We
surmise that this model implies a Wolf-Rayet progenitor for the remnant. We
also present infrared flux upper limits for the central pulsar wind nebula.Comment: 7 pages, 2 tables, 4 figures, uses emulateapj. Accepted for
publication in Ap
Constraints on the luminosity of the stellar remnant in SNR1987A
We obtain photometric constraints on the luminosity of the stellar remnant in
SNR1987A using XMM-Newton and INTEGRAL data. The upper limit in the 2--10 keV
band based on the XMM-Newton data is L<5*10^{34}erg/s. We note, however, that
the optical depth of the envelope is still high in the XMM-Newton band,
therefore, this upper limit does not constrain the true unabsorbed luminosity
of the central source. The optical depth is expected to be small in the hard
X-ray band of the IBIS telescope aboard the INTEGRAL observatory, therefore it
provides an unobscured look at the stellar remnant. We did not detect
statistically significant emission from SN1987A in the 20-60 keV band with the
upper limit of L<1.1*10^{36}erg/s. We also obtained an upper limit on the mass
of radioactive 44Ti M(44Ti)<10^{-3}Msun.Comment: 5 pages, 3 figures, accepted for publication in Astronomy Letter
Nuclear spin-lattice relaxation rate in the D+iD superconducting state: implications for CoO superconductor
We calculated the nuclear spin-lattice relaxation rate for the D+iD
superconducting state with impurities. We found that small amount of unitary
impurities quickly produces the residual density of states inside the gap. As a
result, the T-linear behavior in 1/T is observed at low temperatures. Our
results show that the D+iD pairing symmetry of the superconducting state of
NaCoOH O is compatible with recent Co 1/T
experiments of several groups.Comment: 5 pages, 4 figures, minor change
Searching for the pulsar in G18.95-1.1: Discovery of an X-ray point source and associated synchrotron nebula with Chandra
Using the Chandra X-ray Observatory, we have pinpointed the location of a
faint X-ray point source (CXOUJ182913.1-125113) and an associated diffuse
nebula in the composite supernova remnant G18.95-1.1. These objects appear to
be the long-sought pulsar and its wind nebula. The X-ray spectrum of the point
source is best described by an absorbed powerlaw model with Gamma=1.6 and an
N_H of ~1x10^(22) cm^(-2). This model predicts a relatively low unabsorbed
X-ray luminosity of about L_X (0.5-8.0keV) = 4.1x10^(31)D_2^2 erg s^(-1), where
D_2 is the distance in units of 2kpc. The best-fitted model of the diffuse
nebula is a combination of thermal (kT = 0.48keV) and non-thermal (1.4 < Gamma
< 1.9) emission. The unabsorbed X-ray luminosity of L_X = 5.4x10^(33)D_2^2 erg
s^(-1) in the 0.5-8keV energy band seems to be largely dominated by the thermal
component from the SNR, providing 87% of L_X in this band. No radio or X-ray
pulsations have been reported for CXOUJ182913.1-125113. If we assume an age of
~5300yr for G18.95-1.1 and use the X-ray luminosity for the pulsar and the wind
nebula together with the relationship between spin-down luminosity (via
magnetic dipole radiation) and period, we estimate the pulsar's period to be P
= 0.4s. Compared to other rotation-powered pulsars, a magnetic field of
2.2x10^(13)G is implied by its location in the P-Pdot diagram, a value which is
close to that of the quantum critical field.Comment: 8 pages, 3 Figures, accepted for publication in Ap
X-Ray Synchrotron Emitting Fe-Rich Ejecta in SNR RCW 86
Supernova remnants may exhibit both thermal and nonthermal X-ray emission. We
present Chandra observations of RCW 86. Striking differences in the morphology
of X-rays below 1 keV and above 2 keV point to a different physical origin.
Hard X-ray emission is correlated fairly well with the edges of regions of
radio emission, suggesting that these are the locations of shock waves at which
both short-lived X-ray emitting electrons, and longer-lived radio-emitting
electrons, are accelerated. Soft X-rays are spatially well-correlated with
optical emission from nonradiative shocks, which are almost certainly portions
of the outer blast wave. These soft X-rays are well fit with simple thermal
plane-shock models. Harder X-rays show Fe K alpha emission and are well
described with a similar soft thermal component, but a much stronger
synchrotron continuum dominating above 2 keV, and a strong Fe K alpha line.
Quantitative analysis of this line and the surrounding continuum shows that it
cannot be produced by thermal emission from a cosmic-abundance plasma; the
ionization time is too short, as shown both by the low centroid energy (6.4
keV) and the absence of oxygen lines below 1 keV. Instead, a model of a plane
shock into Fe-rich ejecta, with a synchrotron continuum, provides a natural
explanation. This requires that reverse shocks into ejecta be accelerating
electrons to energies of order 50 TeV. We show that maximum energies of this
order can be produced by radiation-limited diffusive shock acceleration at the
reverse shocks.Comment: ApJ, accepted; full resolution images in
http://spider.ipac.caltech.edu/staff/rho/rcw86chandra.p
XMM-Newton observation of Kepler's supernova remnant
We present the first results coming from the observation of Kepler's
supernova remnant obtained with the EPIC instruments on board the XMM-Newton
satellite. We focus on the images and radial profiles of the emission lines (Si
K, Fe L, Fe K) and of the high energy continuum. Chiefly, the Fe L and Si K
emission-line images are generally consistent with each other and the radial
profiles show that the Si K emission extends to a larger radius than the Fe L
emission (distinctly in the southern part of the remnant). Therefore, in
contrast to Cas A, no inversion of the Si- and Fe-rich ejecta layers is
observed in Kepler. Moreover, the Fe K emission peaks at a smaller radius than
the Fe L emission, which implies that the temperature increases inwards in the
ejecta. The 4-6 keV high energy continuum map shows the same distribution as
the asymmetric emission-line images except in the southeast where there is a
strong additional emission. A two color image of the 4-6 keV and 8-10 keV high
energy continuum illustrates that the hardness variations of the continuum are
weak all along the remnant except in a few knots. The asymmetry in the Fe K
emission-line is not associated with any asymmetry in the Fe K equivalent width
map. The Si K maps lead to the same conclusions. Hence, abundance variations do
not cause the north-south brightness asymmetry. The strong emission in the
north may be due to overdensities in the circumstellar medium. In the
southeastern region of the remnant, the lines have a very low equivalent width
and the X-ray emission is largely nonthermal.Comment: 15 pages, 15 figures, accepted for publication in A&
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