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Browsing IIAP Publications by Title

Browsing IIAP Publications by Title

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  • Optimization of existing centroiding algorithms for Shack Hartmann sensor 
    Vyas, A; Roopashree, M. B; Prasad, B. R (2009)
    Three centroiding techniques to estimate the position of the spots in a Shack Hartmann sensor: Normalized Centre of Gravity (CoG), Iteratively Weighted Centre of Gravity (IWCoG) and Intensity Weighted (IWC) centroiding are ...
  • Optimizing the modal index of Zernike polynomials for regulated phase screen simulation 
    Vyas, A; Roopashree, M. B; Prasad, B. R (SPIE--The International Society for Optical Engineering, 2010-07)
    Simulations of optical wavefronts propagating through the atmosphere are widely used in the design and testing of adaptive optics systems. Phase screens are defined by their spatial and temporal statistics. In many ...
  • Opto-mechanical assembly and ground calibration of LUCI 
    Mathew, J; Nair, B. G; Sriram, S; Kamath, P. U; Prakash, A; Mayuresh, Sarpotdar; Ambily, S; Nirmal, K; Sreejith, A. G; Safonova, M; Murthy, J; Brosch, N (SPIE--The International Society for Optical Engineering, 2018-08-20)
    The Lunar Ultraviolet Cosmic Imager (LUCI) is an innovative all-spherical mirrors telescope, proposed to fly as a scientific UV imaging payload on a lunar mission in collaboration with Indian Aerospace Company-TeamIndus, ...
  • Opto-thermal analysis of a lightweighted mirror for solar telescope 
    Banyal, R. K; Ravindra, B; Chatterjee, S (Optical Society of America, 2013-03-25)
    In this paper, an opto-thermal analysis of a moderately heated lightweighted solar telescope mirror is carried out using 3D finite element analysis (FEA). A physically realistic heat transfer model is developed to account ...
  • Orbit of the spectroscopic binary B Persei 
    Rajamohan, R; Parthasarathy, M (Indian Academy of Sciences, 1975-04)
    Spectroscopic orbital elements are derived for the close binary system b Persei on the basis of forty spectrograms. The period is redetermined as 1.527360 days, and variations in the orbital elements are confirmed by ...
  • Orbital decay of protostellar binaries in molecular clouds 
    Gorti, U; Bhatt, H. C (Royal Astronomical Society, 1996-11)
    The evolution of protostellar binary system is investigated while it is embedded in its parent molecular cloud core and is acted upon by gas drag as a result of dynamical friction. Approximate analytical results are obtained ...
  • Orbital period modulation and spot activity in the RS CVn binary V711 Tauri 
    Muneer, S; Jayakumar, K; Rosario, M. J; Raveendran, A. V; Mekkaden, M. V (EDP Sciences, 2010-10)
    We attempt to establish the real nature of the orbital period variation and its relation to the spot activity of V711 Tau, and determine why the (B–V) colour of the star appears to be nearly independent of its V magnitude. ...
  • Orbital signatures from observed light curves of blazars 
    Mangalam, A; Mohan, Prashanth (Indian Academy of Sciences, 2014-04)
    Variability in active galactic nuclei is observed in ultraviolet to X-ray emission based light curves. This could be attributed to orbital signatures of the plasma that constitutes the accretion flow on the putative disk ...
  • Orbital solutions derived from radial velocities and time delays for four Kepler systems with A/F-type (candidate) hybrid pulsators⋆ 
    Lampens, P; Vermeylen, L; Fremat, Y; Sodor, A; Skarka, M; Samadi-Ghadim, A; Bognar, Zs; Lehmann, H; De Cat, P; Goswami, A; Dumortier, L (EDP Sciences, 2021-03)
    Context. The presence of A/F-type Kepler hybrid stars extending across the entirety of the δ Scuti – γ Doradus instability strips and beyond remains largely unexplained. In order to better understand these particular stars, ...
  • Origin and propagation of extremely high-energy cosmic rays 
    Bhattacharjee, P; Sigl, G. G (Elsevier, 2000-04)
    Cosmic ray particles with energies in excess of 10**20 eV have been detected. The sources as well as the physical mechanism(s) responsible for endowing cosmic ray particles with such enormous energies are unknown. This ...
  • The Origin of Dust Polarization in the Orion Bar 
    Gouellec, Valentin J. M. Le; Andersson, B-G; Archana Soam; Schirmer, Thiébaut; Michail, Joseph M.; Lopez-Rodriguez, Enrique; Flores, Sophia; Chuss, David T.; Vaillancourt, John E.; Hoang, Thiem; Lazarian, Alex (American Astronomical Society, 2023-07-10)
    The linear polarization of thermal dust emission provides a powerful tool to probe interstellar and circumstellar magnetic fields, because aspherical grains tend to align themselves with magnetic field lines. While the ...
  • Origin of Lithium Enrichment in K Giants 
    Bharat Kumar, Y; Reddy, B. E; Lambert, D. L (Institute of Physics Publishing, 2011-03-20)
    In this Letter, we report on a low-resolution spectroscopic survey for Li-rich K giants among 2000 low-mass (M ≤ 3 M sun) giants spanning the luminosity range from below to above the luminosity of the clump. Fifteen new ...
  • Origin of MeV gamma-ray emissions from blazars 
    Ghosh, K. K; Ramsey, B. D; Sivaram, C (Elsevier Science B. V, 1999-06)
    We have developed a model for MeV emission from blazars that involves the production of MeV gamma-rays through Inverse Compton (IC) scattering of electrons in the blob of a jet, with the UV photons of the accretion disk. ...
  • Origin of quantum-mechanical complementarity without momentum back action in atom-interferometry experiments 
    Unnikrishnan, C. S (The American Physical Society, 2000-07)
    We identify the physical origin of the loss of interference pattern in the which-path atom-interferometery experiments that have been discussed widely. The origin of complementarity between the which-path information and ...
  • Origin of Quasi-periodic Pulsation at the Base of a Kink-unstable Jet 
    Mishra, S. K; Sangal, Kartika; Kayshap, Pradeep; Jelinek, Petr; Srivastava, A. K; Rajaguru, S. P (American Astronomical Society, 2023-03-10)
    We studied a blowout jet that occurred at the west limb of the Sun on 2014 August 29 using high-resolution imaging/spectroscopic observations provided by the Solar Dynamics Observatory/Atmospheric Imaging Assembly and ...
  • Origin of short-period (30-300 s) Doppler frequency fluctuations of lower F region reflections in the equatorial electrojet region 
    Sastri, J. H; Ramesh, K. B; Rao, J. V. S. V; Somayajulu, V. V (American Geophysical Union, 1991-12)
    Measurements of phase path P of lower F-region reflections at normal incidence at Kodaikanal revealed the ubiquitous presence of 30-300-s quasi-sinusoidal variations in the time rate of change of phase path, P (Doppler ...
  • Origin of spatial variations of scattering polarization in the wings of the Ca I 4227 Å line 
    Sampoorna, M; Stenflo, J. O; Nagendra, K. N; Bianda, M; Ramelli, R; Anusha, L. S (The American Astronomical Society, 2009-07-10)
    Polarization that is produced by coherent scattering can be modified by magnetic fields via the Hanle effect. This has opened a window to explorations of solar magnetism in parameter domains not accessible to the Zeeman ...
  • Origin of the broadband emission from the transition blazar B2 1308+326 
    Pandey, Ashwani; Kushwaha, Pankaj; Wiita, Paul J; Prince, Raj; Czerny, Bożena; Stalin, C. S (EDP Sciences, 2024-01)
    Context. Transition blazars exhibit a shift from one subclass to the next during different flux states. It is therefore crucial to study them to understand the underlying physics of blazars. Aims. We probe the origin of ...
  • Origin of the highest energy cosmic rays 
    Bhattacharjee, P (Indian Academy of Sciences, 1996-10)
    After briefly recalling the history of discovery of cosmic rays, the present statns of the subject is discussed. Cosmic-ray particles with energy exceeding 1020 eV have been detected. The origin of cosmic rays remains ...
  • Origin of the proper motion and spin of pulsars 
    Cowsik, R (The European Southern Observatory, 1998-12)
    It is suggested that the proper motion and the spin of pulsars at birth are causally connected. Accordingly, the observed mean values of these parameters can be attributed to the recoil momentum and torque impulse imparted ...

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