Search for muons from the direction of cygnus X-3

Muons and multimuons detected in the Fréjus underground nucleon decay detector between February 1984 and January 1986 have been analyzed. No excess events are observed in the direction of Cygnus X-3, which yields a 90% confidence level upper flux limit of 0.8 × 10⁻¹² cm⁻² s⁻¹, for an average rock overburden of 5000 hg cm⁻² corresponding to energies ⪆ 3 TeV. Using the 4.79 h periodicity of Cygnus X-3, no signal is found in any phase interval.     

The rms-flux relation of Cyg X-2 in the horizontal branch

We have investigated the relation between the root mean square (rms) variability and the X-ray flux (rms-flux relation) of the Z source Cyg X-2, and as well the energy dependence based on the Rossi X-ray Timing Explorer (RXTE) observations. We currently focus on the horizontal branch (HB), due to the negative correlation in flux of the soft and the hard X-rays. The rms-flux correlation has energy dependence as follows: positive at hard X-rays (above 10 keV) but negative at soft X-rays (below 10 keV). This provides a feature different from the previous one, and may be suggestive of different origins of X-rays below and above 10 keV. Nevertheless, the overall spectrum can be well fitted with a model consisting of a blackbody and Comptonization components, but the fitting results do not reveal any features around 10 keV that could account for such a change in the rms-flux relation.     

On the capture of muons in atoms

In previous calculations on the capture of negative muons in atoms we used the average energy loss per unit path length as a frictional force in the classical equations of motion. In the present note it is shown that the rare events where the muon, because of its high velocity in the inner parts of the atom, loses an energy which is larger than its total energy, are important for the average stopping power. For the calculation of capture ratios these large energy losses should be treated separately. The results differ significantly from those obtained previously, and are in better agreement with experiment.     

On the change of polarization of positive muons in alkali halides

Positive muons implanted in nonconducting solids form with high probability hydrogenlike muonium atoms (µ ⁺ e ^–) with properties similar to those ofU ₂-centers. The influence of superhyperfine interactions with neighbor nuclei on the evolution of the polarization of the muon is investigated theoretically. The resulting muon polarization in longitudinal magnetic fields is calculated for muonicU ₂-centers in some alkali halides.     

Characterizing direction of coupling from experimental observations

We demonstrate that the direction of coupling of two interacting self-sustained electronic oscillators can be determined from the realizations of their signals. In our experiments, two electronic generators, operating in a periodic or a chaotic state, were subject to symmetrical or unidirectional coupling. In data processing, first the phases have been extracted from the observed signals and then the directionality of coupling was quantitatively estimated from the analysis of mutual dependence of the phase dynamics.     

On the hyperfine field values measured at positive muons in metals

The enhancement of conduction electron density at the position of a positive muon implanted into a metal is calculated in a simple model. Some problems in the interpretation of muon spin frequencies in ferromagnets are pointed out.     

On total capture rate of negative muons in4He

Total capture rate ofμ ^? in⁴He is calculated using a modified Irving wave function, whose parameters are obtained from a variational calculation of the binding energy of⁴He using a central velocity-dependent potential.     

Optical observations of Scorpius X-1 in 2008: Evidence of rapid variability

Optical observations of Sco X-1 with exposure times around 0.5 s were performed with the 1.56 m telescope of the Shanghai Astronomical Observatory in 2008. With these observations, we studied the fluctuation of the optical flux on three short timescales (5, 10, 100 s). We found that the standard deviations of fluctuations on these three timescales differ from those of Gaussian distributions by 7 Sigma, 5 Sigma and 3 Sigma, respectively. The result suggests that the variations in the intensity on these short timescales differ from pure statistical fluctuations, which, we suggest, is due to the intrinsic variability in the optical emission.

     

On the feasibility of using positive muons as probes of defect structure

A self-consistent calculation based on the density functional formalism yields the spin density at a muon in a vacant lattice site, which is significantly different from that at a muon in an interstitial site. It is argued that a precision μ⁺ spin rotation experiment should be able to detect the difference in spin density.     

The first results of observations of acoustic signals generated by cosmic ray muons in a seismically stressed medium

The first results of observations of acoustic signals generated by high-energy muons of extensive air showers, which propagate in a seismically stressed medium are presented. The cosmophysical method for monitoring the volume stressed state is tested using the experimental setup developed in the earthquake-prone region of Almaty at the Tien Shan High-Altitude Scientific Station of the Lebedev Physical Institute. High-amplitude acoustic signals correlated with the passage and interaction of muon groups in the Earth’s crust are detected for the first time.     

Solar diurnal anisotropy measured using muons in GRAPES-3 experiment in 2006

The GRAPES-3 experiment at Ooty contains a large-area (560 m²) tracking muon detector. This detector consists of 16 modules, each 35 m² in area, that are grouped into four supermodules of 140 m² each. The threshold energy of muons is sec(θ) GeV along a direction with zenith angle θ and the angular resolution of the muon detector is 6°. Typically, it records ~4×10⁹ muons every day. The muon detector has been operating uninterruptedly since 2001, thus providing a high statistics record of the cosmic ray flux as a function of time over one decade. However, prior to using these data, the muon rate has to be corrected for two important atmospheric effects, namely, variations in atmospheric pressure and temperature. Because of the near equatorial location of Ooty (11.4°N), the seasonal variations in the atmospheric temperature are relatively small and shall be ignored here. Due to proximity to the equator, the pressure changes at Ooty display a dominant 12 h periodic behaviour in addition to other seasonal changes. Here, we discuss various aspects of a novel method for accurate pressure measurement and subsequent corrections applied to the GRAPES-3 muon data to correct these pressure-induced variations. The pressure-corrected muon data are used to measure the profile of the solar diurnal anisotropy during 2006. The data, when divided into four segments, display significant variation both in the amplitude (~45%) and phase (~42 m) of the solar diurnal anisotropy during 2006, which was a period of relatively low solar activity.