Development of a three channel photometer for UPSO, Naini Tal

The design and performance of a portable three channel photometer installed at the Uttar Pradesh State Observatory (UPSO), Naini Tal is described. The photometer is modular and the whole unit can be disassembled as individual channels such that the system can also be used as a single channel or two channel photometer. The system also has provision to monitor a guide star. The instrument was put into operation since November 1999 on the 1m Sampurnanand telescope at UPSO, Naini Tal. Since then, it is used extensively for the ‘Survey of rapidly oscillating Ap (roAp) stars in the northern sky’ from UPSO. Observational results using this new photometer in its initial phase of operation are discussed. The advantage of having continuous sky measurement is demonstrated.     

Observations of GRS 1915+105 from the USA Experiment on ARGOS

We present first results from a monitoring campaign of GRS 1915+105 undertaken with the USA X-ray timing experiment on the ARGOS satellite. A variety of behaviour has been observed, ranging from low, steady X-ray emission to rapid quasi-periodic flaring on timescales of approximately 10–120 seconds.     

Precision timing measurements of PSR J1012+5307

We present results and applications of high-precision timing measurements of the binary millisecond pulsar J1012+5307. Combining our radio timing measurements with results based on optical observations, we derive complete 3D velocity information for this system. Correcting for Doppler effects, we derive the intrinsic spin parameters of this pulsar and a characteristic age of 8.6±1.9 Gyr . Our upper limit for the orbital eccentricity of only 8×10⁻⁷ (68 per cent confidence level) is the smallest ever measured for a binary system. We demonstrate that this makes the pulsar an ideal laboratory in which to test certain aspects of alternative theories of gravitation. Our precision measurements suggest deviations from a simple pulsar spin-down timing model, which are consistent with timing noise and the extrapolation of the known behaviour of slowly rotating pulsars.     

Performance Evaluation of Bottom-Standing Submerged Breakwaters in Regular Waves Using the Meshless Singular Boundary Method

In this paper, the improved version of the meshless singular boundary method(ISBM) is developed for analyzing the hydrodynamic performance of bottom-standing submerged breakwaters in regular normally incident waves. Both the single and dual prismatic breakwaters of rectangular and trapezoidal forms are examined. Only the impermeable breakwaters are considered in this study. The physical problem is cast in terms of the Laplace equation governing an irrotational flow and incompressible fluid motion with the appropriate mixed-type boundary conditions, and it is solved numerically using the ISBM. The numerical results are presented in terms of the hydrodynamic quantities of reflection and transmission coefficients. The values are first validated against the data of previous studies, computed, and discussed for a variety of structural conditions, including the height, width, and spacing of breakwater submergence. An excellent agreement is observed between the ISBM results and those of other methods. The breakwater width is found to feature marginal effects compared with the height. The present method is shown to accurately predict the resonant conditions at which the maximum reflection and transmission occur. The trapezoidal breakwaters are found to generally present a wide spectrum of reflections, suggesting that they would function better than the rectangular breakwaters. The dual breakwater systems are confirmed to perform much better than single structures.     

High-Resolution Near-Infrared Observations of NGC 1068

We present near-infrared observations of NGC 1068 obtained with the SHARP camera at the ESO 3.5 m telescope, and with SHARP II attached to the COME-ON+ adaptive optics system at the ESO 3.6 m telescope. From the SHARP observations we obtain a K band image of the stellar bar with 0.″4 resolution, and an upper limit to the size of the nuclear K band source of 0.″05 (3.5 pc). The adaptive optics observations are used to determine the position of the infrared nucleus with respect to the visible continuum. The centroid of the 5000 to 9000 Å continuum is displaced 0.″23 ± 0.″10 to the east and 0.″41 ± 0.″10 to the north of the K bank peak.     

Nuclear Aspects of the Solar Neutrino Problem

The present status of the nuclear reaction rates determining the solar neutrino flux is discussed. This includes the reaction rates for the two branching ratios of the three pp-chains involving the reactions 3He(3He,2p)4He and 3He(4He,γ)7Be for the first branching, and 7Be(e−, νe)7Li and 7Be(p, γ)8B for the second branching. Mainly we will concentrate on the basic nuclear reaction p + p → D + e+ + νe of the pp-chains. This reaction rate can only be determined using the theoretical methods. The present status of the application of the relativistic field theory model of the deuteron for this reaction will be discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

CAN WE OBSERVE THE TEMPERATURE INHOMOGENEITIES AND MAGNETIC FLUX TUBES AS THE FINE STRUCTURE ON THE EXTREME LIMB OF THE SUN?

Fine structure of brightness inhomogeneities with I r.m.s. = 2.9% was discovered on the extreme limb of the Sun on the best quality white-light photographs obtained at the Soviet Stratospheric Solar Observatory. The concept is that temperature inhomogeneities are responsible for the limb structure. The real value T r.m.s. = 109K is required to explain our observations. Another possible explanation is that small-scale magnetic flux tubes with the realistic filling factor f* = 1% are the source of the limb brightness fluctuations.     

Comet P/Shoemaker-Levy 9 Collision with Jupiter: A Model of G-Site Dust Composition

Scattering models of aerosol particles at the G-impact site (18 July1994) are presented for a number of likely compositional candidates. Two differing dust particle population distribution functions are taken, along with varying aerosol cloud densities, leading to differing optical depths. A number of models including graphite, amorphous carbon, astrophysical silicate, water ice and a number of organic compounds are discussed, but no single material provides a fully satisfactory fit to the published observations. A porous silicate/graphite composite is found to provide a good fit to the spectral data. This revised version was published online in July 2006 with corrections to the Cover Date.