Astronomy & Atrophysics

We present the radio light curves of lensed images of the gravitational lens B1422+231. The observations have been carried out using the VLA at 8.4 and 15 GHz over a period of 197 days. We describe a method to estimate the time delay from the observed light curves. Using this method, our cross-correlation analysis shows that the time delay between images B and A is 1.5$\pm$1.4d, between A and C is 7.6$\pm$2.5d, between B and C is 8.2$\pm$2.0d. When applied to other lensed systems with measured time delays our new method gives comparable results.

"The Left-handed metamaterial (LHM) is found to exhibit counter-intuitive electromagnetic properties [1] and its phase velocity (Vp
) and group velocity (Vg ) are 1800 apart [1, 2], thus they show negative refractive index [3]. We have been experimenting on the structured meta-materials for negative refractive index at microwave frequencies. The paper is not regarding the
experiment, but nature of energy momentum transport in NRM. The negative refraction is under the experimental research for past decade [3, 5]. If a pulse of EM radiation is launched inside a
negative refractive index material (NRM), it gets squeezed sharpened, and similarly a spherical wave front in positive indexed media gets flattened as it propagates inside the NRM [4], yet it is
interesting if in the meta-material parlance particle-wave theory be founded. Here we give possible classical explanations to these counterintuitive phenomena and also a new explanations
regarding energy momentum if applied to this negative indexed material; new definitions."

Giant Meter wave Radio Telescope (GMRT) has been designed to operate at six frequency bands centered at 50 MHz, 150 MHz, 235 MHz, 327 MHz, 610 MHz and L-Band extending from 1000
MHz to 1450 MHz. L-band is split into four sub-bands centered at 1060 MHz, 1170 MHz, 1280 MHz and 1390 MHz, each with bandwidth of 120 MHz . The 150 MHz, 235 MHz and 327 MHz
bands have about 40 MHz bandwidth and 610 MHz band has about 60 MHz bandwidth. Lower frequency bands from 150 MHz to 610 MHz have dual circular polarization channels (Right
Hand Circular and Left Hand Circular) which have been conveniently named as CH1 and CH2 respectively.
This report attempts to describe design of switch filter bank for upgraded 325 MHz (250-500 MHz) front end system using MeTaMaterial (MTM) Zeroth Order Resonator (ZOR)
technique. The objective of using MTM-ZOR technique is to reduce the filter size is compare to the conventional design. It is observed that using MTM-ZOR technique the filter size is reduced
by a factor of six times compare to couple line design and four times compare to hairpin design.Fig.1. shows block diagram of upgrade 250-500 MHz front end system with switch filter bank.
The switch filter bank consists of four sub bands, 240-340 MHz, 300-400 MHz, 360-460 MHz, and 420-520 MHz along with 250-500 MHz main band pass filter. Each sub band is 100 MHz
bandwidth (6 dB points). The document covers fundamental of various type of filters, detail Chatterjee, S Page 5 design of MTM-ZOR based band pass filter and its compression with the conventional microstrip filters. The design is done using ADS-2012 software which work on Method of moments. Rogers RT droid board RT 6010 is used for this design.

Metamaterial (MTM) is an artificial composite material for which we can change its electromagnetic properties [1]. The equivalent circuit approach of MTM was developed by Caloz and Itoh [2] and Sanada et al. [3], and this approach has led to the concept of composite right- and left-handed (CRLH) materials. This concept fully takes into account the parasitic right-handed (RH) effects, which is unavoidable in a practical application. The zeroth-order resonator (ZOR) has the mode number zero, and its resonator length is invariant of its wavelength. Sanada et al. [3] first proposed MTM-ZOR and realized it in microstrip configuration. Using the MTM-ZOR technique, several researchers [4]???[8] have designed band pass filters (BPFs) in different frequency bands.

In this paper we have carried out numerical simulation and experimental characterization of two variants of SR (Spiral resonator) viz. TTSR (Two-Turn Spiral Resonator) and NBSR (Non Bianisotropic spiral resonator). The numerical simulation of these develop magnetic inclusion structures are done with commercially available Finite Element Method (FEM) based Ansys HFSS-13 simulation software, and transmission experiment using S-parameter retrieval technique. The experimental characterization of those fabricated structures is used in the parallel plate waveguide experiment (not reported earlier) and then validate our experimental results with the Ansys HFSS-13 simulation software; which in not available in any published literature. Keywords: MTM (Meta-material), LHM (left handed material), TTSR (Two Turn Spiral Resonator), NBSR (Non Bianisotropic Spiral Resonator), MNG (Mue Negative Material).

A programme has been in progress in our laboratory to determine the performance of a cylindrical proportional counter filled with argon or xenon at pressures up to 30 atmospheres, using methane as the quenching agent. The successful operation of a prototype counter has led to the design of a large area balloon-borne detector for hard xray astronomy. The ultra high pressure in an array of cylindrical proportional counter modules, together with the large dimensions possible, will enable us to fabricate a detector with very high efficiency and sensitivity, capable of extending its energy response well beyond the limits of contemporary flow detectors. The details of our investigations and the proposed detector are described.

Large area multi-layer proportional chambers filled with Xenon have been developed for the study of cosmic X-ray sources in 20-100 keV range. The X-ray teleecop~consists of two such~etect 8rs, each having an effective area of 1200 cm and equipped with a 5 x 5 FWHM collimator, mounted on a servo-controlled orientation platform for making pointed mode observations. Superior energy resolution of the Xenon detectors, being 10 % FWHM at 22 kaV, makes them well suited for detection of cyclotron emission lines in the spectra of X-ray pulsars. The X-ray light curves and energy spectrum of the 4.8 hour binary Cyg X-3, observed in a balloon flight in March 1986 is described.

We present the results of low frequency radio observations of the X-ray binaries, Cygnus X-1 and Cygnus X-3, during different X-ray states. The low frequency observations were made for the first time for these sources at 0.61 and 1.28 GHz using the Giant Meter-wave Radio Telescope (GMRT) between 2003 and 2004. Both Cyg X-1 and Cyg X-3 are highly variable at low radio frequencies. We also compare our data with the observations at 15 GHz conducted by the Ryle telescope. Spectral turnover is seen for both the sources below 2 GHz. The data suggest that the change in the radio flux density in both the sources is correlated to the X-ray hardness ratio and follows a similar behavior pattern.

We have a continuing programme of spectral and temporal studies of a variety of galactic and extragalactic sources in the 20-200 keV band using a large area scintillation counter telescope. The observations of NGC 5506, a Seyfert type 2 galaxy, taken on three occasions during the 1998-2000 period suggest that not only source luminosity varies by a factor of $10, but also there is a marked change in the spectral index. The data is consistent with a systematic long-term periodic variation. Our analysis of the all sky monitor light curve suggests a 41.12-day period in the source intensity. This paper presents the spectral parameters in the hard X-ray region and proposes that the observed behaviour of the source can be explained on the basis of a binary black hole model for the core activity of the source.

The HETE-2 mission has been highly productive. It has observed more than 250 GRBs so far. It is currently localizing 25-30 GRBs per year, and has localized 43 GRBs to date. Twenty-one of these localizations have led to the detection of X-ray, optical, or radio afterglows, and as of now, 11 of the bursts with afterglows have known redshifts. HETE-2 has confirmed the connection between GRBs and Type Ic supernovae, a singular achievement and certainly one of the scientific highlights of the mission so far. It has established that the isotropic-equivalent energies and luminosities of GRBs are strongly correlated with redshift, implying that GRBs and their progenitors evolve strongly with redshift. Both of these results have profound implications for the nature of GRB progenitors and for the use of GRBs as a probe of cosmology and the early universe. HETE-2 has placed severe constraints on any X-ray or optical afterglow of a short GRB. It is also solving the mystery of "optically dark" GRBs, and revealing the nature of X-ray flashes. 1pc

Three novel bacterial strains, PVAS-1(T), B3W22(T) and B8W22(T), were isolated from cryotubes used to collect air samples at altitudes of between 27 and 41 km. Based on phenotypic characteristics, chemotaxonomic features, DNA-DNA hybridization with the nearest phylogenetic neighbours and phylogenetic analysis based on partial 16S rRNA gene sequences (PVAS-1(T), 1196 nt; B3W22(T), 1541 nt; B8W22(T), 1533 nt), the three strains were identified as representing novel species, and the names proposed are Janibacter hoylei sp. nov. (type strain PVAS-1(T) =MTCC 8307(T) =DSM 21601(T) =CCUG 56714(T)), Bacillus isronensis sp. nov. (type strain B3W22(T) =MTCC 7902(T) =JCM 13838(T)) and Bacillus aryabhattai sp. nov. (type strain B8W22(T) =MTCC 7755(T) =JCM 13839(T)).

Experimental results on the intensity, energy spectrum and time variations in hard X-ray emission from Cyg X-1 based on a balloon observation made on 1971, April 6 from Hyderabad (India) are described. The average energy spectrum of Cyg X-1 in the 22-154 keV interval on 1971 April 6 is best represented by a power law dN/dE = (5.41 • 1.53) E-(1.92~~176 photons cm-z s-1 keV-x which is in very good agreement with the spectrum of Cyg X-1 derived from an earlier observation made by us on 1969 April 16 in the 25-151 keV band and given by dN/dE = (3.54 4-2.44) E-(1.sg•176 photons cm-2 s-1 keV-L A thermal bremsstrahlung spectrum fails to give a good fit over the entire energy range for both the observations. Comparison with the observations of other investigators shows that almost all balloon experiments consistently give a spectrum of ~ E-2, while below 20 keV the spectrum varies from E-L7 to E-5. There is some indication of a break in the Cyg X-1 spectrum around 20 keV. Spectral analysis of data in different time intervals for the 1971 April 6 flight demonstrates that while the source intensity varies over time scales of a few minutes, there is no appreciable variation in the spectral slope. Analysis of various hard X-ray observations for long term variations shows that over a period of about a week the intensity of Cyg X-1 varies upto a factor of four. The binary model proposed by Dolan is examined and the difficulties in explaining the observed features of Cyg X-1 by this model are pointed out.