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Browsing IIAP Publications by Title

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  • Optical Transmission Spectra of Hot Jupiters: Effects of Scattering 
    Sengupta, S; Chakrabarty, Aritra; Tinetti, Giovanna (IOP Publishing, 2020-02-01)
    We present new grids of transmission spectra for hot Jupiters by solving the multiple-scattering radiative transfer equations with non-zero scattering albedo instead of using the Beer–Bouguer–Lambert law for the change in ...
  • Optical Variability of BL Lacertae during the Major Outburst of 1997 
    Ghosh, K. K; Ramsey, B. D; Sadun, A. C; Soundararajaperumal, S; Wang, J (The American Astronomical Society, 2000-07)
    We have undertaken an investigation of recent flux variability in BL Lac. We present optical observations taken over 22 nights documenting major as well as minor outbursts. This has been combined, for purposes of multifrequency ...
  • Optical Variability of Blazars 
    Ghosh, K. K; Ramsey, B. D; Sadun, A. C; Soundararajaperumal, S (The American Astronomical Society, 2000-03)
    In this paper we show the results of our monitoring the flux variability of 15 blazars, within the redshift range of 0.07-2.06, all with a visual magnitude range between 14 and 20 mag. Because blazars have displayed ...
  • Optical variability of narrow-line and broad-line Seyfert 1 galaxies 
    Rakshit, S; Stalin, C. S (IOP Publishing, 2017-05)
    We studied the optical variability ( OV ) of a large sample of narrow-line Seyfert 1 ( NLSy1 ) and broad-line Seyfert 1 ( BLSy1 ) galaxies with z  <  0.8 to investigate any differences in their OV ...
  • Optical variability of radio-intermediate quasars 
    Goyal, Arti; Gopal-Krishna; Joshi, S; Sagar, R; Wiita, Paul J; Anupama, G. C; Sahu, D. K (Blackwell Publishing, 2010-02)
    We report the results of our intensive intranight optical monitoring of eight optically bright `radio-intermediate quasars' (RIQs) having flat or inverted radio spectra. The monitoring was carried out in R band on 25 nights ...
  • An Optical, Dual-Beam, Automated Medium Resolution Spectropolarimeter for the Vainu Bappu Telescope 
    Chakraborty, P; Vasundhara, R (Springer, 2003-03)
    Fabrication of an optical dual-beam spectropolarimeter as an add-on facility to an existing astronomical spectrograph at the Vainu Bappu Telescope is described. The polarimetric optics consists of a superachromatic ...
  • Optical/IR studies of Be stars in NGC 6834 with emphasis on two specific stars 
    Mathew, B; Varricatt, W. P; Subramaniam, A; Ashok, N. M; Banerjee, D. P. K (IOP Publishing, 2014-09)
  • 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. ...

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