2,517 research outputs found
The neutron star soft X-ray transient 1H1905+000 in quiescence
In this Paper we report on our analysis of a ~25 ksec. Chandra X-ray
observation of the neutron star soft X-ray transient (SXT) 1H1905+000 in
quiescence. Furthermore, we discuss our findings of the analysis of optical
photometric observations which we obtained using the Magellan telescope and
photometric and spectroscopic observations which we obtained using the Very
Large Telescope at Paranal. The X-ray counterpart of 1H1905+000 was not
detected in our Chandra data, with a 95 per cent confidence limit to the source
count rate of 1.2x10^-4 counts s^-1. For different spectral models this yields
an upper limit on the luminosity of 1.8x10^31 erg s^-1 (for an upper limit on
the distance of 10 kpc.) This luminosity limit makes 1H1905+000 the faintest
neutron star SXT in quiescence observed to date. The neutron star luminosity is
so low that it is similar to the lowest luminosities derived for black hole
SXTs in quiescence. This low luminosity for a neutron star SXT challanges the
hypothesis presented in the literature that black hole SXTs in quiescence have
lower luminosities than neutron star SXTs as a result of the presence of a
black hole event horizon. Furthermore, the limit on the neutron star luminosity
obtained less than 20 years after the outburst has ceased, constrains the
thermal conductivity of the neutron star crust. Finally, the neutron star core
must be so cold that unless the time averaged mass accretion rate is lower than
2x10^-12 M_sun yr^-1, core cooling has to proceed via enhanced neutrino
emission processes. We derive a limit on the absolute I-band magnitude of the
quiescent counterpart of M_I>7.8 assuming the source is at 10 kpc. This is in
line with 1H1905+000 being an ultra-compact X-ray binary, as has been proposed
based on the low outburst V-band absolute magnitude.Comment: 10 pages, 5 figures, accepted for publication in MNRA
Compositional Design and Verification of a Multi-Agent System for One-to-Many Negotiation
A compositional verification method for multi-agent systems is presented and applied to a multi-agent system for one-to-many negotiation in the domain of load balancing of electricity use. Advantages of the method are that the complexity of the verification process is managed by compositionality, and that parts of the proofs can be reused in relation to reuse of components
The correlations between the spin frequencies and kHz QPOs of Neutron Stars in LMXBs
We studied the correlations between spin frequencies and kilohertz
quasi-periodic oscillations (kHz QPOs) in neutron star low mass X-ray binaries.
The updated data of kHz QPOs and spin frequencies are statistically analyzed.
We found that when two simultaneous kHz QPOs are present in the power spectrum,
the minimum frequency of upper kHz QPO is at least 1.3 times larger than the
spin frequency, i.e. \nu_{s}<\nu_{2min}/1.3. We also found that the average kHz
QPO peak separation in 6 Atoll sources anti-correlates with the spin frequency
in the form \lan\dn\ran = -(0.19\pm0.05)\ns+(389.40\pm21.67)Hz. If we shifted
this correlation in the direction of the peak separation by a factor of 1.5,
this correlation matches the data points of the two accretion powered
millisecond X-ray pulsars, SAX J1808.4-3658 and XTE J1807-294.Comment: 4 pages, 2 figures, accepted for publication in A&
Deliberate evolution in multi-agent systems
and their applications. SMC is sponsored by the Netherlands Organization for Scientific Research (NWO). CWI is a member o
The search for decaying Dark Matter
We propose an X-ray mission called Xenia to search for decaying superweakly
interacting Dark Matter particles (super-WIMP) with a mass in the keV range.
The mission and its observation plan are capable of providing a major break
through in our understanding of the nature of Dark Matter (DM). It will
confirm, or reject, predictions of a number of particle physics models by
increasing the sensitivity of the search for decaying DM by about two orders of
magnitude through a wide-field imaging X-ray spectrometer in combination with a
dedicated observation program.
The proposed mission will provide unique limits on the mixing angle and mass
of neutral leptons, right handed partners of neutrinos, which are important
Dark Matter candidates. The existence of these particles is strongly motivated
by observed neutrino flavor oscillations and the problem of baryon asymmetry of
the Universe.
In super-WIMP models, the details of the formation of the cosmic web are
different from those of LambdaCDM. The proposed mission will, in addition to
the search for decaying Dark Matter, provide crucial insight into the nature of
DM by studying the structure of the "cosmic web". This will be done by
searching for missing baryons in emission, and by using gamma-ray bursts as
backlight to observe the warm-hot intergalactic media in absorption.Comment: A white paper submitted in response to the Fundamental Physics
Roadmap Advisory Team (FPR-AT) Call for White Paper
Magnetism and Structural Distortion in the La0.7Sr0.3MnO3 Metallic Ferromagnet
Neutron scattering studies on a single crystal of the highly-correlated
electron system, La1-xSrxMnO3 with x~0.3, have been carried out elucidating
both the spin and lattice dynamics of this metallic ferromagnet. We report a
large measured value of the spin wave stiffness constant, which directly shows
that the electron transfer energy of the d band is large. The spin dynamics,
including magnetic critical scattering, demonstrate that this material behaves
similar to other typical metallic ferromagnets such as Fe or Ni. The crystal
structure is rhombohedral, as previously reported, for all temperatures studied
(below ~425K). We have observed new superlattice peaks which show that the
primary rhombohedral lattice distortion arises from oxygen octahedra rotations
resulting in an R-3c structure. The superlattice reflection intensities which
are very sensitive to structural changes are independent of temperature
demonstrating that there is no primary lattice distortion anomaly at the
magnetic transition temperature, Tc = 378.1 K, however there is a lattice
contraction.Comment: Submitted to Phys. Rev. B. (03Aug95) Uuencoded gz-compressed .tar
file of Postscript text (12 pages) and 6 figures. Also available by WWW from
http://insti.physics.sunysb.edu/~mmartin/ under my list of publications or by
e-mail reques
High-field AFMR in single-crystalline La_{0.95}Sr_{0.05}MnO_3: Experimental evidence for the existence of a canted magnetic structure
High-field antiferromagnetic-resonance (AFMR) spectra were obtained in the
frequency range 60 GHz < \nu < 700 GHz and for magnetic fields up to 8 T in
twin-free single crystals of La_{0.95}Sr_{0.05}MnO_3. At low temperatures two
antiferromagnetic modes were detected, which reveal different excitation
conditions and magnetic field dependencies. No splitting of these modes was
observed for any orientation of the static magnetic field excluding the
phase-separation scenario for this composition. Instead, the full data set
including the anisotropic magnetization can be well described using a
two-sublattice model of a canted antiferromagnetic structure.Comment: 4 pages, 3 figure
Low Satisfaction with Normative Life Domains in Adolescents with Anorexia Nervosa
OBJECTIVE: Low satisfaction with normative life domains might be an important factor in the persistence of anorexia nervosa (AN). Initial evidence in nonâclinical samples showed that lower satisfaction with normative life domains was related to more intense eating disorder symptoms. As a critical next step, the current study examined satisfaction with normative life domains in a clinical sample. Specifically, the present study tested whether adolescents with AN reported lower satisfaction with normative life domains than adolescents without an eating disorder. METHOD: Adolescents with AN (nâ=â69) and adolescents without an eating disorder matched on age, gender and educational level (nâ=â69) completed the Brief Multidimensional Students' Life Satisfaction Scale to assess satisfaction with five life domains (family, friendships, school, self and living location) and life in general. RESULTS: Adolescents with AN reported significantly lower satisfaction with normative life domains than the comparison group. Subsequent analyses showed that this overall group difference was primarily driven by adolescents with AN reporting lower satisfaction with the self, school experience and life in general. CONCLUSIONS: Findings supported the hypothesis that adolescents with AN show relatively low satisfaction with meaningful, nonâANârelated life domains. This points to the potential relevance of enhancing satisfaction with specific life domains to optimize treatment effectiveness
Satisfaction with normative life domains and the course of anorexia nervosa
OBJECTIVE: Satisfaction with normative life domains has been proposed as an important factor in the persistence of anorexia nervosa (AN). Initial evidence from a cross-sectional study indicated that individuals with AN reported lower satisfaction with normative life domains than individuals without an eating disorder. As an important next step in understanding causal relations, the present study used a longitudinal design to examine whether an improvement in AN symptoms is paralleled by an increase in satisfaction with normative life domains from baseline to follow-up and whether relatively low satisfaction with normative life domains at baseline is related to less improvement in AN symptoms. METHODS: During baseline and at 1-year follow-up, adolescents with AN (N = 69) completed the Brief Multidimensional Students' Life Satisfaction Scale to measure satisfaction with normative life domains (e.g., friendships, school experience). Furthermore, eating disorder symptoms and BMI were measured. RESULTS: Improvement in eating disorder symptoms, but not in BMI, was paralleled by an increase in satisfaction with normative life domains. Relatively low satisfaction with normative life domains at baseline was not prospectively related to less improvement in eating disorder symptoms or BMI at follow-up. DISCUSSION: Our findings provide initial evidence that satisfaction with normative life domains is a malleable factor which fluctuates with symptom severity in AN. The results of this exploratory study point to the relevance of examining whether targeting satisfactory engagement with specific life domains optimizes treatment effectiveness. PUBLIC SIGNIFICANCE: We explored whether an improvement in anorexia nervosa symptoms from start of treatment to 1-year follow-up would be paralleled by an increase in satisfaction with normative life domains. Improvement in eating disorder symptoms (but not BMI) was indeed related to a concurrent increase in satisfaction with normative life domains. These preliminary results point to the promising possibility that targeting satisfactory engagement with specific life domains may potentially enhance treatment effectiveness
On the "Mandelbrot set" for a pair of linear maps and complex Bernoulli convolutions
We consider the "Mandelbrot set" for pairs of complex linear maps,
introduced by Barnsley and Harrington in 1985 and studied by Bousch, Bandt and
others. It is defined as the set of parameters in the unit disk such
that the attractor of the IFS is
connected. We show that a non-trivial portion of near the imaginary axis is
contained in the closure of its interior (it is conjectured that all non-real
points of are in the closure of the set of interior points of ). Next we
turn to the attractors themselves and to natural measures
supported on them. These measures are the complex analogs of
much-studied infinite Bernoulli convolutions. Extending the results of Erd\"os
and Garsia, we demonstrate how certain classes of complex algebraic integers
give rise to singular and absolutely continuous measures . Next we
investigate the Hausdorff dimension and measure of , for
in the set , for Lebesgue-a.e. . We also obtain partial results on
the absolute continuity of for a.e. of modulus greater
than .Comment: 22 pages, 5 figure
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