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Browsing by Author "Giridhar, S"

Browsing by Author "Giridhar, S"

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  • Performance results of HESP physical model 
    Anantha, Ch; Sivarani, T; Jones, D; Giridhar, S; Grobler, D; Jakobsson, R (2017-02)
    As a continuation to the published work on model based calibration technique with HESP(Hanle Echelle Spectrograph) as a case study, in this paper we present the performance results of the technique. We also describe how ...
  • Period changes in the RR Lyrae stars of NGC 6171 (M107) 
    Arellano Ferro, A; Rosenzweig, P; Luna, A; Deras, D; Muneer, S; Giridhar, S; Michel, R (WILEY-VCH Verlag GmbH & Co., 2018-02)
    Based on photometric data obtained between 1935 and 2017, O −C diagrams were built for 22 RR Lyrae stars in the globular cluster NGC 6171, leading to the discovery of secular period changes in four variables for which we ...
  • A photometric study of F-type stars of high galactic latitude 
    Ferro, A. A; Giridhar, S; Chavez, M; Parrao, L (European Southern Observatory, 1989-04)
    Photometry in the O I 7774 A line and the uvbybeta system is presented for a group of high Galactic latitude F-type luminosity type I stars. The results indicate that the candidates are high gravity near solar Fe/H abundance ...
  • Physical parameters of RR Lyrae stars in NGC 6171 
    Deras, D; Arellano Ferro, A; Muneer, S; Giridhar, S; Michel, R (WILEY-VCH Verlag GmbH & Co., 2018-08)
    We present an analysis of VI CCD time series photometry of the globular cluster NGC 6171. The main goal is to determine individual physical parameters for single‐mode RR Lyrae stars present in the field of view of our ...
  • Physical parameters of RR Lyrae stars in the globular cluster NGC 5466: The Oosterhoff dichotomy 
    Rojas Lopez, V; Arellano Ferro, A; Giridhar, S; Bramich, D. M (Instituto de Astronomía, 2006-06)
    The highlights of CCD photometry of RR Lyrae stars in NGC 5466 are presented. The image subtraction method (Bramich et al. 2005) was used. The Fourier light curve decomposition, lead to an average [Fe/H]=-1.88+/-0.3 and a ...
  • The progress in the study of post-AGB stars 
    Giridhar, S (Astronomical Society of India, 2011)
    Post-AGB stars represent a crucial phase in the evolution of low and intermediate stars where rapid change in the surface composition of the star and its circumstellar envelope takes place. We summarize recent developments ...
  • Recent advances in RV Tauri stars 
    Giridhar, S (Indian Academy of Sciences, 2020-12)
    The availability of multi-wavelength observations and parallaxes from the space missions and very comprehensive models of AGB evolution that include the accretion of matter from the circumbinary disc have strongly impacted ...
  • Respect - software for reduction of spectroscopic data 
    Anupama, G. C; Prabhu, T. P; Giridhar, S (Tata Institute of Fundamental Research, 1988)
    We describe the interactive software package RESPECT developed for reductions of astronomical spectroscopic data at the Vainu Bappu Observatory, Kavalur. Each command of RESPECT performs a simple operation on a one-dimensional ...
  • Respect - Software Package for Reduction of Astronomical Spectra 
    Prabhu, T. P; Anupama, G. C; Giridhar, S (Astronomical Society of Indian, 1987)
    The interactive software package RESPECT developed for reducing astronomical spectroscopic data at Vainu Bappu Observatory (VBO), Kavalur, is described. Each command of RESPECT performs a simple operation on a one-dimensional ...
  • A Revised Calibration of the M-V-W(O I 7774) Relationship using Hipparcos Data: Its Application to Cepheids and Evolved Stars 
    Ferro, A. A; Giridhar, S; Arellano, E. R (Instituto de Astronomía, Universidad Nacional Autónoma de México, 2003-04)
    A new calibration of the MV-W(O I 7774) relationship has been calculated using better reddening and distance estimates for a sample of 27 calibrator stars of spectral types A to G, based on accurate parallaxes and proper ...
  • Revisiting the variable star population in NGC 6229 and the structure of the horizontal branch 
    Arellano Ferro, A; Mancera Pina, P. E; Bramich, D. M; Giridhar, S; Ahumada, J. A; Kains, N; Kuppuswamy, K (Oxford University Press on behalf of the Royal Astronomical Society, 2015-09-01)
    We report an analysis of new V and I CCD time series photometry of the distant globular cluster NGC 6229. The principal aims were to explore the field of the cluster in search of new variables, and to Fourier decompose the ...
  • RR Lyrae stars and the horizontal branch of NGC 5904 (M5) 
    Ferro, A. A; Luna, A; Bramich, D. M; Giridhar, S; Ahumada, J. A; Muneer, S (Springer, 2016-05)
    We report the distance and [Fe/H] value for the globular cluster NGC 5904 (M5) derived from the Fourier decomposition of the light curves of selected RRab and RRc stars. The aim in doing this was to bring these ...
  • RR Lyrae Stars in the Globular Cluster Palomar 2 
    Ferro, A. Arellano; Fierro, Bustos; Muneer, S; Giridhar, S (Universidad Nacional Autonoma De Mexico, 2023-04)
    A CCD VI imaging time-series over 11-year is employed to explore the light curves of stars in the field of Palomar 2. We discovered 20 RRab and 1 RRc variables. A revision of Gaia-DR3 data enabled us to identify 10 more ...
  • Spectral Analysis of Selected Cepheids and the Galactic Distribution of Metalicity 
    Giridhar, S (Indian Institute of Astrophysics, Bangalore, 1982-10)
  • Spectral Classification: Old and Contemporary 
    Giridhar, S (Springer, 2010)
    Beginning with a historical account of the spectral classification, its refinement through additional criteria is presented. The line strengths and ratios used in two dimensional classifications of each spectral class are ...
  • Spectral Variations of DY Cen 
    Giridhar, S; Kameswara Rao, N; Lambert, D. L (Indaian Academy of Sciences, 1996-06)
    Two high resolution spectra of the hot RCrB star DY Cen in the red region are compared. The photospheric absorption lines show a radial velocity variation of 12 km s(sup -1) between 1989 July and 1992 May. Emission components ...
  • Spectroscopic analysis of four post-AGB candidates 
    Molina, R. E; Giridhar, S; Pereira, C. B; Arellano Ferro, A; Muneer, S (Institute de Astronomia, 2014-10)
    We have done a detailed abundance analysis of four unexplored cand idate post- Asymptotic Giant Branch(AGB) stars IRAS 13110- 6629, IRAS 175 79 - 3121, IRAS 18321- 1401 and IRAS 18489- 0629 using high resolution spectra. ...
  • Spectroscopic studies of R CrB during light minima - Absorption spectrum 
    Kameswara Rao, N; Giridhar, S; Ashoka, B. N (Royal Astronomical Society, 1990-05)
    R CrB was observed during the 1986 shallow minimum to study the spectral changes taking place during light minimum as compared with the spectrum at maximum light. The absorption spectrum at this minimum is very similar to ...
  • Spectroscopic studies of selected F-G supergiants 
    Giridhar, S; Arellano, F. A; Parrao, L (Astronomical Society of India, 1998)
  • Spectroscopic studies of the southern Cepheid β Dor 
    Giridhar, S (Universidad Nacional Autonoma De Mexico, 1987-05)
    Fine analysis of the southern Cepheid β Dor has been conducted at different phases with the aim to derive atmospheric parameters at those phases. Atmospheric abundances have been derived for Fe group elements and s-process ...

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