IIAP Publications: Recent submissions

  • A spectroscopic study of the hybrid pulsator Gamma Pegasi 
    Pandey, C. P; Morel, T; Briquet, M; Jayakumar, K; Bisht, S; Sanwal, B. B (Austrian Academy of Sciences Press, 2011-02)
    The recent detection of both pressure and high-order gravity modes in the clas- sical B-type pulsator γ Pegasi offers promising prospects for probing its internal structure through seismic studies. To aid further modelling ...
  • Optical Microvariability of Blazars 
    Ghosh, K. K; Kim, C; Ramsey, B. D; Soundararajaperumal, S (Korean Astronomical Society, 2001-04)
    We present the results of optical differential photometry of five blazars [PKS 0219+428(3C66A), PKS 0235+164(AO 0235+16), H0414+019, PKS 0851+202(OJ 287), and QSO 1807+698(3C371)] that were observed on 7 nights between ...
  • Star Formation Activity in the Galactic H II Complex S255-S257 
    Ojha, D. K; Samal, M. R; Pandey, A. K; Bhatt, B. C; Ghosh, S. K; Sharma, S; Tamura, M; Mohan, V; Zinchenko, I (IOP Publishing, 2011-09-10)
    We present results on the star formation activity of an optically obscured region containing an embedded cluster (S255-IR) and molecular gas between two evolved H II regions, S255 and S257. We have studied the complex using ...
  • The [Fe/H], [C/Fe], and [α/Fe] Distributions of the Boötes I Dwarf Spheroidal Galaxy 
    Lai, D. K; Lee, Y. S; Bolte, M; Lucatello, S; Beers, T. C; Johnson, J. A; Sivarani, T; Rockosi, C. M (IOP Publishing, 2011-09-01)
    We present the results of a low-resolution spectral abundance study of 25 stars in the Boötes I dwarf spheroidal (dSph) galaxy. The data were obtained with the low resolution imaging spectrometer instrument at Keck Observatory ...
  • Rapid optical variability of TeV blazars 
    Gopal-Krishna; Goyal, A; Joshi, S; Karthick, C; Sagar, R; Wiita, P. J; Anupama, G. C; Sahu, D. K (Wiley-Blackwell, 2011-09)
    In this first systematic attempt to characterize the intranight optical variability (INOV) of TeV-detected blazars, we have monitored a well-defined set of nine TeV blazars on total 26 nights during 2004–10. In this R- or ...
  • Mass of the black hole in the Seyfert 1.5 galaxy H 0507+164 from reverberation mapping 
    Stalin, C. S; Jeyakumar, S; Coziol, R; Pawase, R. S; Thakur, S. S (Wiley-Blackwell, 2011-09)
    We present the results of our optical monitoring campaign of the X-ray source H 0507+164, a low-luminosity Seyfert 1.5 galaxy at a redshift z= 0.018. Spectroscopic observations were carried out during 22 nights in 2007, ...
  • Polarized Line Formation in Multi-dimensional Media. III. Hanle Effect with Partial Frequency Redistribution 
    Anusha, L. S; Nagendra, K. N (IOP Publishing, 2011-09-01)
    In two previous papers, we solved the polarized radiative transfer (RT) equation in multi-dimensional (multi-D) geometries with partial frequency redistribution as the scattering mechanism. We assumed Rayleigh scattering ...
  • Analysis of the Forward-scattering Hanle Effect in the Ca I 4227 Å Line 
    Anusha, L. S; Nagendra, K. N; Bianda, M; Stenflo, J. O; Holzreuter, R; Sampoorna, M; Frisch, H; Ramelli, R; Smitha, H. N (IOP Publishing, 2011-08-20)
    Coherent scattering of limb-darkened radiation is responsible for the generation of the linearly polarized spectrum of the Sun (the Second Solar Spectrum). This Second Solar Spectrum is usually observed near the limb of ...
  • Is the Post-AGB Star SAO 40039 Mildly Hydrogen-Deficient? 
    Sumangala Rao, S; Pandey, G; Lambert, D. L; Giridhar, S (IOP Publishing, 2011-08-10)
    We have conducted an LTE abundance analysis for SAO 40039, a warm post-AGB star whose spectrum is known to show surprisingly strong He I lines for its effective temperature and has been suspected of being H-deficient and ...
  • Analysis of Coronal Green Line Profiles: Evidence of Excess Blueshifts 
    Raju, K. P; Chandrasekhar, T; Ashok, N. M (IOP Publishing, 2011-08-01)
    Coronal green line (Fe XIV 5303 Å) profiles were obtained from Fabry-Perot interferometric observations of the solar corona during the total solar eclipse of 2001 June 21 from Lusaka, Zambia. The instrumental width is about ...
  • India's tryst with modern astronomy 
    Anathpindika, S (Wiley-Blackwell, 2011-08)
    Research in astronomy within India has increased substantially over the past two decades, catapulted by growing public awareness of the subject, and aided by the efforts of amateur astronomy groups in several towns and ...
  • X-ray spectral properties of Seyfert galaxies and the unification scheme 
    Singh, V; Shastri, P; Risaliti, G (EDP Sciences, 2011-08)
    Context. The unification scheme of Seyfert galaxies predicts that the observed differences between types 1 and 2 Seyfert galaxies are solely due to the differing orientations of the toroidal-shaped obscuring material around ...
  • Evolution of magnetic field twist and tilt in active region NOAA 10930 
    Ravindra, B; Venkatakrishnan, P; Tiwari, S. K (World Scientific Publishing Company, 2010)
    Magnetic twist of the active region has been measured over a decade using photospheric vector field data, chromospheric Hα data, and coronal loop data. The twist and tilt of the active regions have been measured at the ...
  • Probing the physical properties of directly imaged gas giant exoplanets through polarization 
    Marley, Mark S; Sengupta, S (Wiley-Blackwell, 2011-11)
    It is becoming clear that the atmospheres of the young, self-luminous extrasolar gi- ant planets imaged to date are dusty. Planets with dusty atmospheres may exhibit detectable amounts of linear polarization in the ...
  • Towards Low Cost turbulence generator for AO testing: Utility, control and stability 
    Roopashree, M. B; Vyas, A; Krishnan, S. M; Sriram, R; Siva Shankar Sai, S; Prasad, B. R (Optical Society of America, 2011-07)
    We demonstrate and characterize an effective, statistically repeatable atmospheric turbulence generator with the aim of testing a 2m class telescope adaptive optics system in a cost effective manner.
  • Grid size optimization for atmospheric turbulence phase screen simulations 
    Roopashree, M. B; Vyas, A; Prasad, B. R (Optical Society of America, 2011-07)
    Atmospheric phase screens are used for numerical evaluation of large telescope systems. In this paper, we optimized the grid size of the simulated phase screens in terms of the error in the structure function assuming a ...
  • Spectral line polarization with angle-dependent partial frequency redistribution III. Single scattering approximation for the Hanle effect 
    Sampoorna, M (EDP Sciences, 2011-08)
    Context. The solar limb observations in spectral lines display evidence of linear polarization, caused by non-magnetic resonance scattering process. This polarization is modified by weak magnetic fields – the process of ...
  • Multi-dither Shack Hartmann sensor for large telescopes: A numerical performance evaluation 
    Vyas, A; Roopashree, M. B; Prasad, B. R (Optical Society of America, 2011-07)
    Wavefront reconstruction accuracy strongly depends on the way the wavefront distortion points match the wavefront sensing locations. A multi-dither sensor largely improves the wavefront reconstruction accuracy in large ...
  • Evaluation of the performance of centroiding algorithms with varying spot size: case of WFS calibration for the TMT NFIRAOS 
    Vyas, A; Ellerbroek, B. L; Roopashree, M. B; Andersen, D. R; Prasad, B. R (Optical Society of America, 2011-07)
    In this AO system, a low-bandwidth truth wavefront sensor detects biases in the laser-guide-star-based wavefront measurement, arising from uncertainties in the sodium layer profile. Here, the performance of centroiding ...
  • Automated ROI selection and calibration of a microlens array using a MEMS CDM 
    Roopashree, M. B; Vyas, A; Prasad, B. R (Optical Society of America, 2011-07)
    A method of automated selection of region of interest for sensing using a microlens array by imposing Zernikes on a 140 actuator deformable mirror is presented. The positional sensitivity and optimal noise removal techniques ...

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