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Chandrasekhar T. Ashok N. M. Tej Anandamayee Mondal Soumen Watson P. V. 《Earth, Moon, and Planets》1998,81(2):111-121
During the recent apparition of comet Hale—Bopp (1995 O1) near infrared photometric observations were carried out in the J,
H, K filter bands and also in the 3.0—3.4 μm region at the 1.2 m telescope at Gurushikkar, India. The effective temperature
of the comet was substantially higher than the equilibrium blackbody temperature. A mean superheat value of 1.83 was derived
in the post-perihelion phase which implies that a large fraction of the grain population are made up of small and hot grains
with radii <0.5 μm. High albedo values of ∼0.4 were also derived in the scattering angle range 135° to 160° which could explain
the unusual brightness of comet Hale—Bopp.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Anandmayee Tej T. Chandrasekhar 《Monthly notices of the Royal Astronomical Society》2000,317(3):687-696
High angular resolution measurements of a sample of 15 M giants at 2.2 μm by the technique of lunar occultation are presented in this paper. We obtain angular diameters for 11 sources of which five are the first diameter measurements. For these resolved sources we have estimated the effective temperatures, which are consistent with previous calibrations. For the other four sources we put the first upper limits on their angular sizes to be 2 mas. Two sources, namely IRC+20090 and IRC+20067, yield appreciably low temperatures, which could point to their possible Mira nature. For sources with Hipparcos parallax measurements, we have calculated the linear radii. 相似文献
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The lithostratigraphy, depositional environment and age of the Marwar Supergroup have been reviewed in the light of report
of δ13C depletion recorded in the carbonates of the Bilara Group (middle part of Marwar Supergroup) and discovery of trilobite-like
trace fossils from the ·Red bedsŽ of Nagaur Group (upper part of Marwar Supergroup). The δ13C depletion observed in Bilara carbonates is not a result of glaciation rather due to rapid burial and poor water circulation
in the low energy water of the protected basin. Secondly, the trace fossils are, in fact, traces of notostracan crustaceans
found in shallow fluvial and shallow lacustrine environment. The present paper also records a spiral, burrowing trace-fossil,
possibly Gyrolithes, from a cross-bedded sandstone of the Jodhpur Group. 相似文献
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P. Manoj S. Vig G. Maheswar U. S. Kamath A. Tej 《Journal of Astrophysics and Astronomy》2016,37(4):38
Stars and planetary systems are formed out of molecular clouds in the interstellar medium. Although the sequence of steps involved in star formation are generally known, a comprehensive theory which describes the details of the processes that drive formation of stars is still missing. The Square Kilometre Array (SKA), with its unprecedented sensitivity and angular resolution, will play a major role in filling these gaps in our understanding. In this article, we present a few science cases that the Indian star formation community is interested in pursuing with SKA, which include investigation of AU-sized structures in the neutral ISM, the origin of thermal and non-thermal radio jets from protostars and the accretion history of protostars, and formation of massive stars and their effect on the surrounding medium. 相似文献
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S. Kishore P. K. Misra D. K. Pandey A. K. Jauhri Tej Bahadur S. K. Singh R. S. Chauhan S. K. Tripathi 《Journal of the Geological Society of India》2012,80(2):215-230
The Quaternary sediments of the Aramda Reef Member of the Chaya Formation exposed in the Mojap coast near Mithapur, Gujarat are characterized by well-developed coralline algal build-ups. These algal build-ups are exceptionally rich in coralline algae and corals. In the present paper, thirteen species belonging to eight genera of coralline algae are described. Out of these, seven species (Titanoderma nataliae, Lithophyllum nitorum, Lithophyllum quadratum, Spongites sp. Brandano et al., 2005, Sporolithon lvovicum, Mesophyllum fructiferum and Lithothamnion praefruticulosum) are the new records for India. Four species (Titanoderma pustulatum, Sporolithon intermedium, Mesophyllum commune and Phymatolithon sp.) are first time recorded from the study area. Among the major framework builders of coralline algae of the Aramda Reef Member are Lithophyllum, Titanoderma, Sporolithon, Mesophyllum and Lithothamnion. 相似文献
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