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Browsing by Author "Giridhar, S"

Browsing by Author "Giridhar, S"

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  • Identification of metal-poor stars using the artificial neural network 
    Giridhar, S; Goswami, A; Kunder, A; Muneer, S; Selvakumar, G (EDP Sciences, 2013-08)
    Context. Identification of metal-poor stars among field stars is extremely useful for studying the structure and evolution of the Galaxy and of external galaxies. Aims. We search for metal-poor stars using the artificial ...
  • Image processing facilities at Vainu Bappu observatory 
    Giridhar, S; Bhattacharyya, J. C; Kutty, K. N (Tata Institute of Fundamental Research, 1988)
    Need for application of Image processing techniques in astronomical studies in optical wavelengths and special advantages accruing thereby are discussed. The paper describes various image processing facilities that are ...
  • Important parameters of four small-amplitude cepheids from uvby photometry 
    Arellano Ferro, A; Giridhar, S; Parrao, L (Konkoly Observatory, 1987-08)
  • An internally consistent set of oscillator strengths for Fe I lines 
    Giridhar, S; Ferro, A. A (Indian Academy of Sciences, 1989-03)
    An extensive set of internally consistent oscillator strength values for Fe I lines is compiled using literature data and scaling the oscillator strengths derived by different workers to that of Blackwell and his coworkers. ...
  • Investigation of variable star candidates in the globular cluster NGC 5024 (M53) 
    Bramich, D. M; Arellano Ferro, A; Figuera Jaimes, R; Giridhar, S (Wiley-Blackwell, 2012-08)
    We have performed a careful investigation of the 74 candidate variable stars presented by Safonova & Stalin. For this purpose we used our data base of imaging and light curves from Arellano Ferro et al. We find that two ...
  • Is LR SCO and RCB star? 
    Giridhar, S; Kameswara Rao, N; Lambert, D. L (The Observatory, 1990-08)
  • 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 ...
  • A Li-rich post-AGB star HD 172481 
    Giridhar, S; Arellano Ferro, A; Mathias, P (Astronomical Society of India, 2001)
    Our abundance analysis of this post-AGB candidate star confirms that the HD 172481 is indeed a post-AGB star. It belongs to an important, but relatively rare class of post-AGB stars showing Li I features in their spectra. ...
  • A new discussion on the M(v) - W(O I 7774 A) relationship for F-G stars in the light of high-resolution data 
    Arellano Ferro, A; Giridhar, S; Goswami, A (Royal Astronomical Society, 1991-05)
    High-resolution CCD data and a large group of F-G stars of fundamentally determined distances are used here to investigate the intrinsic nature of the M(v) - W(O I) relation and the effect of other atmospheric parameters ...
  • A new search for variable stars in the globular cluster NGC 6366 
    Ferro, A. A; Giridhar, S; Lopez, V. R; Figuera, R; Bramich, D. M; Rosenzweig, P (Instituto de Astronomía, 2008-10)
    New CCD photometry of NGC 6366 has lead to the discovery of some variable stars. Two possible Anomalous Cepheids (or Pop II Cepheids), three long period variables, one SX Phe and one eclipsing binary have been found. Also, ...
  • A new study of the variable star population in the Hercules globular cluster (M13; NGC 6205) 
    Deras, D; Arellano Ferro, A; Lazaro, C; Bustos Fierro, I. H; Calderon, J. H; Muneer, S; Giridhar, S (Oxford University Press on behalf of the Royal Astronomical Society, 2019-06)
    We present the results from VI CCD time-series photometry of the globular cluster M13 (NGC 6205). From the Fourier decomposition of the light curves of RRab and RRc stars we found an average metallicity of [Fe/H]zw = −1.58 ...
  • New variables in M5 (NGC 5904) and some identification corrections 
    Arellano Ferro, A; Bramich, D. M; Giridhar, S; Luna, A; Muneer, S (Konkoly Observatory, 2015-04)
    We report twelve variables not previously detected in the globular cluster M5 (NGC 5904); one SX Phe and eleven semi-regular variables (SR). Their identifications, equatorial coordinates, ephemerides, and light curves are ...
  • NGC 6712: the variable star population of a tidally disrupted globular cluster 
    Deras, D; Arellano Ferro, A; Lazaro, C; Bustos Fierro, I. H; Calderon, J. H; Muneer, S; Giridhar, S (Oxford University Press on behalf of the Royal Astronomical Society, 2020-04)
    We present an analysis of VI CCD time-series photometry of globular cluster NGC 6712. Our main goal is to study the variable star population as indicators of the cluster mean physical parameters. We employed the Fourier ...
  • 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 ...

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