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Browsing by Author "Giridhar, S"

Browsing by Author "Giridhar, S"

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  • Detailed analysis of the variable star population in the globular cluster NGC 7006 
    Arellano Ferro, A; Rojas Galindo, F. C; Bustos Fierro, I. H; Muneer, S; Yepez, M. A; Giridhar, S (Oxford University Press on behalf of Royal Astronomical Society, 2023-02)
    A 5-yr CCD photometric VI time series of NGC 7006 is employed to perform a detailed analysis of the known population of variable stars. In the process, we have corrected inconsistent classifications, sky coordinates and ...
  • A detailed census of variable stars in the globular cluster NGC 6333 (M9) from CCD differential photometry 
    Arellano Ferro, A; Bramich, D. M; Jaimes, R. F; Giridhar, S; Kains, N; Kuppuswamy, K; Jorgensen, U. G; Alsubai, K. A; Andersen, J. M; Bozza, V; Browne, P; Novati, S. C; Damerdji, Y; Diehl, C; Dominik, M; Dreizler, S; Elyiv, A; Giannini, E; Harpsoe, K; Hessman, F. V; Hinse, T. C; Hundertmark, M; Juncher, D; Kerins, E; Korhonen, H; Liebig, C; Mancini, L; Mathiasen, M; Penny, M. T; Rabus, M; Rahvar, S; Ricci, D; Scarpetta, G; Skottfelt, J; Snodgrass, C; Southworth, J; Surdej, J; Tregloan-Reed, J; Vilela, C; Wertz, O (Oxford University Press on behalf of the Royal Astronomical Society, 2013-09-11)
    We report CCD V and I time series photometry of the globular cluster NGC 6333 (M9). The technique of difference image analysis has been used, which enables photometric precision better than 0.05 mag for stars brighter than ...
  • Difference image analysis: extension to a spatially varying photometric scale factor and other considerations 
    Bramich, D. M; Horne, Keith; Albrow, M. D; Tsapras, Y; Snodgrass, C; Street, R. A; Hundertmark, M; Kains, N; Arellano Ferro, A; Figuera Jaimes, R; Giridhar, S (Oxford University Press on behalf of the Royal Astronomical Society, 2013-01-21)
    We present a general framework for matching the point-spread function (PSF), photometric scaling and sky background between two images, a subject which is commonly referred to as difference image analysis (DIA). We introduce ...
  • Elemental Abundances and Atmospheric Parameters of Seven F-G Supergiants 
    Giridhar, S; Ferro, A; Parrao, L (Astronomical Society of the Pacific, 1997-10)
    Spectroscopic abundance determinations for a sample of seven F-G stars have been carried out. The majority of them have large galactic latitudes. One objective in deriving spectroscopic abundances is to differentiate evolved ...
  • Emission Spectrum of Hot R CrB star Mv Sgr 
    Kameswara Rao, N; Houziaux, L; Giridhar, S (Indian Academy Sciences, 1990-03)
    The new spectroscopic observation of MV Sgr obtained at ESO in 1987july shows enhanced emission lines of He I , λ 3889, [S II ] λ 4068 relative to the observations discussed by Jeffrey et al. (1988). The presence of [SII] ...
  • Estimating the parameters of globular cluster M 30 (NGC 7099) from time-series photometry 
    Kains, N; Bramich, D. M; Ferro, A. A; Jaimes, R. F; Jorgensen, U. G; Giridhar, S; Penny, M. T; Alsubai, K. A; Andersen, J. M; Bozza, V; Browne, P; Burgdorf, M; Novati, S. C; Damerdji, Y; Diehl, C; Dodds, P; Dominik, M; Elyiv, A; Fang, X.-S; Giannini, E; Gu, S.-H; Hardis, S; Harpsoe, K; Hinse, T. C; Hornstrup, A; Hundertmark, M; Jessen-Hansen, J; Juncher, D; Kerins, E; Kjeldsen, H; Korhonen, H; Liebig, C; Lund, M. N; Lundkvist, M; Mancini, L; Martin, R; Mathiasen, M; Rabus, M; Rahvar, S; Ricci, D; Sahu, D. K; Scarpetta, G; Skottfelt, J; Snodgrass, C; Southworth, J; Surdej, J; Tregloan-Reed, J; Vilela, C; Wertz, O; Williams, A (EDP Sciences, 2013-07)
    Aims. We present the analysis of 26 nights of V and I time-series observations from 2011 and 2012 of the globular cluster M 30 (NGC 7099). We used our data to search for variable stars in this cluster and refine the periods ...
  • The evolution of the Milky Way: new insights from open clusters 
    Reddy, A. B. S; Lambert, D. L; Giridhar, S (Oxford University Press on behalf of the Royal Astronomical Society, 2016-12)
    We have collected high-dispersion echelle spectra of red giant members in the 12 open clusters (OCs) and derived stellar parameters and chemical abundances for 26 species by either line equivalent widths or synthetic ...
  • Evolution of the optical spectrum of SN 1987a in the Large Magellanic Cloud 
    Ashoka, B. N; Anupama, G. C; Prabhu, T. P; Giridhar, S; Ghosh, K. K; Jain, S. K; Pati, A. K; Kameswara Rao, N (Indian Academy of Sciences, 1987-06)
    The evolution of the spectrum of SN 1987a is traced from 1987 February 26 to March 31. Based on the low-resolution spectroscopic data the authors identify the lines of H, He I, Na I, Fe II, Sc II, Ca II which are known to ...
  • Exploiting large surveys for galactic astronomy 
    Corbally, C. J; Bailer-Jones, C. A. L; Giridhar, S; Lloyd Evans, T. H (Cambridge University Press, 2007-08)
    This summary of JD13, Exploiting large surveys for Galactic astronomy, is based on the talks that were given during the meeting and/or submitted to the full proceedings which appeared in MemSAI 77 no. 4, 2006. The electronic ...
  • Exploring the variable stars in the globular cluster NGC 5024 (M53): new RR Lyrae and SX Phoenicis stars 
    Arellano Ferro, A; Figuera Jaimes, R; Giridhar, S; Bramich, D. M; Hernández Santisteban, J. V; Kuppuswamy, K (Wiley-Blackwell, 2011-09)
    We report CCD V and I time series photometry of the globular cluster NGC 5024 (M53). The technique of difference image analysis has been used which enables photometric precisions better than 10 mmag for stars brighter than ...
  • Fiber-fed echelle spectrometer of the 2.34 meter Vainu Bappu Telescope 
    Kameswara Rao, N; Sriram, S; Gabriel, F; Prasad, B. R; Samson, J. P. A; Jayakumar, K; Srinivasan, R; Mahesh, P. K; Giridhar, S (Anita Publications, 2004-12)
    The optical design and performance of high resolution fiber-fed echelle spectrometer for the 2.34 meter Vainu Bappu Telescope (VBT) is described. An optical fiber of core 100 J-Lm and length 45 meter is used to link the ...
  • Further spectroscopic observations of SN 1987A 
    Anupama, G. C; Prabhu, T. P; Ghosh, K. K; Ashoka, B. N; Giridhar, S (Elsevier, 1988)
    Spectroscopic observations of SN 1987a obtained during 1987 August 30 – September 8 from Vainu Bappu Observatory, Kavalur, are presented; the spectrum is compared and contrasted with the spectra recorded at earlier epochs. ...
  • Galactic chemical evolution and chemical tagging with open clusters 
    Reddy, A. B. S; Giridhar, S; Lambert, D. L (Indian Academy of Sciences, 2020-12)
    The article presents the consolidated results drawn from the chemical composition studies of Reddy et al. (2012, 2013, 2015, 2016) and Reddy & Lambert (2019), who through the high-dispersion echelle spectra (R=60000) of ...
  • The Globular cluster M10: reassessment of stellar membership, distance, and age using its variable and HB stars 
    Arellano Ferro, A; Yepez, M. A; Muneer, S; Bustos Fierro, I. H; Schroder, K. P; Giridhar, S; Calderon, J. H (Oxford University Press on behalf of the Royal Astronomical Society, 2020-12)
    Time-series VI CCD photometry of the globular cluster M10 (NGC 6254) is employed to perform a detailed identification, inspection of their light curves, their classification, and their cluster membership, of all the known ...
  • Hanle echelle spectrograph: design and performance 
    Sriram, S; Amit Kumar; Arun Surya; Sivarani, T; Giridhar, S; Kathiravan, S; Anand, M. N; Jones, D; Grobler, D; Jakobsson, R; Anantha, Ch; Athira Unni; Angchuk, D; Tsewang, D; Gyalson, T (SPIE-The International Society for Optical Engineering, 2018-07-06)
    Hanle echelle spectrograph (HESP) is a high resolution, bench mounted, fiber-fed spectrograph at visible wavelengths. The instrument was recently installed at the 2m Himalayan Chandra Telescope (HCT), located at Indian ...
  • HD 34700: A new T Tauri double-lined spectroscopic binary 
    Arellano, F. A; Giridhar, S (The European Southern Observatory, 2003-09)
    We find the star HD 34700 to be a double-lined spectroscopic binary. We also identify it as a weak-line T Tauri object. The spectra of both components are very similar and both show the Li I feature at 6708 Å. Strong ...
  • The He II 5411 Å velocity curve of the Wolf-Rayet eclipsing system HD 214419 
    Giridhar, S (Indian Institute of Astrophysics, 1978)
    A velocity curve of the Wolf-Rayet eclipsing system HD 214419 is obtained from measures on prismatic spectra of the Hell 5411 emission line. The shape of the velocity curve is unlike that obtained for Hell 4686. The emission ...
  • High resolution spectroscopy of R Coronae Borealis during the 1988-1989 minimum 
    Lambert, D. L; Kameswara Rao, N; Giridhar, S (Indian Academy of Sciences, 1990-12)
    Moderate-resolution spectra of the C2 Swan 0-1 bandhead, the Na I D lines and the K I resonance lines near 7660 A obtained at minimum light during the 1988-1989 decline of R CrB are discussed and interpreted in terms of a ...
  • High Resolution Spectroscopy of the Semi-Regular Variable LR Sco 
    Giridhar, S; Kameswara Rao, N; Lambert, D. L (Indian Academy of Sciences, 1992)
    A detailed spectroscopic investigation of LR Sco which was earlier misclassified as R CrB star is made. Atmospheric parameters and elemental abundances are determined using detailed depth-dependent model atmospheres and ...
  • High resolution spectroscopy with a 10-m class telescope 
    Giridhar, S (Astronomical Society of India, 2000)

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