排序方式： 共有28条查询结果，搜索用时 46 毫秒
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P. Kharb D. V. Lal V. Singh J. Bagchi C. H. Ishwara Chandra A. Hota C. Konar Y. Wadadekar P. Shastri M. Das K. Baliyan B. B. Nath M. Pandey-Pommier 《Journal of Astrophysics and Astronomy》2016,37(4):34
We present detailed science cases that a large fraction of the Indian AGN community is interested in pursuing with the upcoming Square Kilometre Array (SKA). These interests range from understanding low luminosity active galactic nuclei in the nearby Universe to powerful radio galaxies at high redshifts. Important unresolved science questions in AGN physics are discussed. Ongoing low-frequency surveys with the SKA pathfinder telescope GMRT, are highlighted. 相似文献
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One interesting method of constraining the dense matter Equations of State is to measure the advancement of the periastron of the orbit of a binary radio pulsar (when it belongs to a double neutron star system). There is a great deal of interest on applicability of this procedure to the double pulsar system PSR J0737-3039 (A/B). Although the above method can be applied to PSR A in future within some limitations, for PSR B this method cannot be applied. On the other hand, the study of genesis of PSR B might be useful in this connection and its low mass might be an indication that it could be a strange star. 相似文献
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Manjari Bagchi Rachid Ouyed Jan Staff Subharthi Ray Mira Dey † Jishnu Dey ‡ 《Monthly notices of the Royal Astronomical Society》2008,387(1):115-120
We study the effects of temperature on strange stars. It is found that the maximum mass of the star decreases with the increase of temperature, as at high temperatures the equations of state become softer. Moreover, if the temperature of a strange star increases, keeping its baryon number fixed, its gravitational mass increases and its radius decreases. This leads to a limiting temperature, where it turns into a black hole. These features are the result of a combined effect of the change of gluon mass and the quark distribution with temperature. We report on a new type of radial oscillation of strange stars, driven by what we call 'chromothermal' instability. We also discuss the relevance of our findings in the astrophysics of core collapse supernovae and gamma-ray bursts. 相似文献
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Ruta Kale K. S. Dwarakanath Joydeep Bagchi Surajit Paul 《Journal of Astrophysics and Astronomy》2011,32(4):533-536
The case of spectacular ring-like double radio relics in the merging, rich galaxy cluster A3376 is of great interest to study
non-thermal phenomena at cluster outskirts. We present the first low frequency (330 and 150 MHz) images of the double relics
using the GMRT. With our GMRT 330 MHz map and the VLA 1400 MHz map (Bagchi et al. 2006), we have constructed and analyzed the distribution of spectral indices over the radio relics. We find flat spectral
indices at the outer edges of both the relics and a gradual steepening of spectral indices toward the inner regions. This
supports the model of outgoing merger shock waves. The eastern relic has a complex morphology and spectral index distribution
toward the inner region. This will be discussed in the context of the effect of large-scale accretion flows on the outgoing
merger shocks as reported in the recent simulations. 相似文献
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Santosh Kumar S. Raju Manjari Pathak Abhishek Pandey 《Journal of the Geological Society of India》2010,75(3):539-548
Late Archaean to Palaeoproterozoic felsic magmatic lithounits exposed in the central part of the Bundelkhand massif have been
mapped and their redox series (magnetite vs ilmenite series) evaluated based on magnetic susceptibility (MS) data. The central
part of Bundelkhand massif comprises of multiple felsic magmatic pulses (∼2600–2200 Ma), commonly represented by coarse grained
granite (CGG-grey granite, CPG-pink granite), medium grained pink granite (MPG), fine grained pink granite (FPG), grey and
pink rhyolites and granite porphyry (GP). However, the pink colour of these felsic rocks is the result of hydrothermal fluid-flushing
leading to potassic alteration of grey granites. MS values of CGG vary from 0.058 to 14.75×10−3 SI with an average of 6.35×10−3 SI, which mostly represent oxidized type, magnetite series (73%) granites involving infracrustal (igneous) source materials.
CPG (av. MS=3.95×10−3 SI) is indeed a pink variety of CGG, the original oxidizing nature of which must have been similar to the bulk of CGG, but
has been moderately to strongly reduced because of distinctly more porphyritic nature together with partial assimilation of
metapelitic (supracrustal) materials, surmicaceous enclaves, carbonaceous material included in the source materials, and to
some extent, induced by hydrothermal and later deformational processes. MPG (av. MS= 1.15×10−3 SI) as lensoidal stock-like bodies intrudes the CPG and represent both magnetite series (18%) and ilmenite series (82%) granites,
which are probably formed by heterogeneous (mixed) source rocks. GP (av. MS=6.26×10−3 SI) occur as dykes (mostly trending NE-SW) intrudes the MPG, CPG and migmatites and bears the nature similar to oxidized
type, magnetite series granite. FPG (av. MS= 0.666×10−3 SI) trending NE-SW occur as lensoid bodies including a large outcrop, is intrusive into both CPG and MPG, and is moderately
to very strongly reduced type, ilmenite series granites, which may be derived by the melting of metapelitic crustal sources.
FPG hosting microgranular (mafic magmatic) enclaves commonly exhibit high MS values (7.31–10.22×10−3 SI), which appear induced by the mixing and mingling of interacting felsic and mafic magmas prevailed in an open system.
Grey (av. MS=10.30×10−3 SI) and pink (av. MS=6.72×10−3 SI) rhyolites represent oxidized type, magnetite series granites, which may have been derived from infracrustal (magmatic)
protoliths. Granite series evaluation of felsic magmatic rocks of central part of Bundelkhand massif strongly suggests their
varied redox conditions (differential oxygen fugacity) mostly intrinsic to magma source regions and partially modified by
hydrothermal and tectonic processes acting upon them. 相似文献
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In this work, we have considered a model of the flat Friedmann–Robertson–Walker (FRW) Universe filled with cold dark matter
and a chameleon field where the scale function is taken as (i) intermediate expansion and (ii) logamediate expansion. In both
cases we find the expressions of the chameleon field, chameleon potential, statefinder parameters, and slow-roll parameters.
Also, it has been shown that the potential always decreases with the chameleon field in both scenarios. The nature of the
slow-roll parameters has been shown diagrammatically. 相似文献
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M. Sinha M. K. Mukhopadhyay P. M. Mitra M. M. Bagchi H. C. Karamkar 《Estuaries and Coasts》1996,19(3):710-722
Construction of the Farakka barrage on the Ganga River in April 1975 to augment water supply to the Calcutta port has brought about a significant increase in freshwater discharge in its distributary, the Hoogly estuary. This has naturally resulted in major changes in the ecology of this estuary, causing modifications in the structure of its fishery resources, fishing pattern, and fish production. This paper presents observations on salinity, plankton, bottom biota, fishery resource, and fish production of different zones of the Hooghly estuary during the period 1982–1992. Comparison with similar studies made before and immediately after commissioning of the Farakka barrage (1975–1977) has revealed that the increased freshwater discharge has resulted in considerable decrease in salinity throughout the estuary. The freshwater zone now extends toward the mouth of the estuary. The true estuarine zone has moved seaward and the marine zone has been restricted to the area near the mouth of the estuary. This has effected major changes in plankton dynamics, sharp decline in the fishery of marine and neritic species in the upper estuary, caused a significant increase in catch ofTenualosa ilisha and an over twofold increase in the average annual fish landings from the estuary as a whole. New zonations have been proposed based on the presently, observed salinity values, which are the most significant factor in determining the fishery of any estuary. An interdisciplinary study of the ecology of the new zones is needed to establish their correct biological characteristics. 相似文献
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Kalyan Kumar Bagchi Sukla Mukherjee Lokenath Debnath 《Pure and Applied Geophysics》1973,111(1):2255-2263
Summary With the aid of the generalized function method, a study is made of the linearized theory of transient development of capillary-gravity waves in an inviscid, incompressible and homogeneous liquid of finite and infinite depth due to an arbitrary oscillating source situated at a finite depth below the undisturbed free surface of the liquid. The initial value problem is solved by using Laplace-Fourier transforms combined with asymptotic methods. The asymptotic solution is found to consist of the steady state and the transient components which are independently modified by surface tension. The latter decays more rapidly as timet due to the presence of surface tension than in the case where surface tension is neglected. It is predicted that the principal effect of surface tension is to increase both the phase and group velocity of the waves and make the energy more readily available among the rapidly travelling progressive surface waves. In addition to the effects of surface tension on the physical properties of the wave motions, our method of solution provides an interesting illustration of the applicability of generalized functions in water wave phenomena. 相似文献
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Yashwant Gupta Poonam Chandra Manjari Bagchi Niruj M. Ramanujam Yogesh Maan Avinash A. Deshpande Siddhartha Bhattacharyya 《Journal of Astrophysics and Astronomy》2016,37(4):37
In the rapidly developing field of study of the transient sky, fast radio transients are perhaps the most exciting objects of scrutiny at present. The SKA, with its wide field-of-view and significant improvement in sensitivity over existing facilities, is expected to detect a plethora of fast transients which, in addition to help resolve the mysteries surrounding their nature and origin, will also lead to other interesting applications in astrophysics. We explore some of these possibilities here, and also emphasize the current status and future plans of the Indian community working in this area, in the context of ongoing work and extension of this to the SKA. 相似文献