Search Publications
On the performance of a dual-beam polarimeter at Kodaikanal Tower Telescope
Singh, Jagdev; Sankarasubramanian, K.; Ramesh, K. B. +4 more
Calibration and characterization of a dual-beam polarimeter installed at Kodaikanal Tower Telescope (KTT) for spectropolarimetric observations are presented in this paper. It was found that a slit width of 48 µ is optimum for the spectrograph setup at KTT and corresponding spectral resolution is 32.47 mÅ. It was demonstrated that the precisi…
On the possibility of gly and ala amino acids on Titan
Saxena, P. P.
In view of the possible production of formaldehyde and acetaldehyde in Titan's atmosphere, the production of α-amino nitriles, the precursors of glycine and alanine amino acids, is explored in the upper atmosphere of Titan. The presence of glycine and alanine amino acids or their precursor amino nitriles can be used as a diagnostic respectively fo…
The Hipparcos mission and galactic open clusters and NGC 7538 star forming regions
Scholz, R. -D.; Piskunov, A. E.; Kharchenko, N. V. +2 more
We present some results of a study of the galactic open cluster population. This study is based on the all-sky catalogue ASCC-2.5 compiled from Tycho-2, Hipparcos and other catalogues. Screening the ASCC-2.5 resulted in the identification of 520 known clusters and the detection of 130 new ones. A uniform combined kinematic-photometric cluster memb…
Morphological analysis of intermediate redshift galaxies using the HST/ACS GOODS survey
Kembhavi, Ajit K.; Rawat, A.
We have been involved in performing photometry and morpholog- ical analysis of a large, complete sample of galaxies in the intermediate redshift range using the high resolution images obtained by the Great Observatories Origins Deep Survey (GOODS) with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). Imaging data is avail…
A model of the stellar radiation field in the UV.
Henry, R. C.; Murthy, Jayant; Sujatha, N. V. +1 more
This work is the first step in a systematic effort to understand and predict the different components of the UV (912 A - 3000 A) radiation field over the entire sky. We have developed a model to predict the ISRF in the UV within a few hundred parsecs of the Sun using the Hipparcos star catalog. We have checked the model through a comparison with t…
Excitation of Solar p-mode Oscillations by Flares
Basu, Sarbani; Antia, H. M.; Ambastha, Ashok
Solar flares release large amounts of energy at different layers of the solar atmosphere. It is, therefore, expected that major flares would be able to excite waves, thereby affecting the p-mode oscillation characteristics. From the analysis of MDI data, we find that power in p-modes appears to increase for some flares, beyond the normal values ex…
On the Rapid Variations of Solar Magnetic Fields
Venkatakrishnan, P.; Kumar, Brajesh; Ravindra, B.
We report on the rapid variations of solar magnetic fields that appear to be enhanced significantly above the background variability, at a few locations within the solar active regions, as observed with the Michelson Doppler Imager (MDI) on board the SOHO spacecraft. The pressure fluctuations estimated to arise from this variability far exceed the…
Solar Cycle Variation in GONG and MDI Data : 1995-2002
Tripathy, S. C.
Both GONG and MDI projects have measured p-mode frequencies of the Sun for more than 7 years. Here we review what we have learnt from the temporal variation of the oscillation frequencie and splitting coefficients.
Geomagnetic storms with H 400nT during 1979-99
Kumar, Santosh; Pratap Yadav, Mahendra
The effect of solar features on geospheric conditions leading to ninety nine geomagnetic storms (GMSs) with H400nT and Ap20 have been investigated using interplanetary magnetic field (IMF), solar wind plasma (SWP) and solar geophysical data (SGD) during the period 1979-99. H, X-ray solar o o flares occured within lower latitudinal zone i.e., 30 N-…
MSX Observations of Diffuse UV Emission in Orion
Price, S. D.; Paxton, L. J.; Henry, R. C. +1 more
We have observed intense diffuse radiation in the UV (1400 Å - 2600 Å) from three fields around M42 in Orion. Intensities of 20000 photons cm-2 sr-1 s-1 Å-1 were observed to the east and west of M42 with 8000 photons cm-2 sr-1 s-1 Å-1 south of the nebula. Enhanced emission, perhaps associated with a nearby complex of molecular clouds observed in C…