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Browsing by Author "Sivarani, T"

Browsing by Author "Sivarani, T"

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  • Li Distribution, Kinematics, and Detailed Abundance Analysis among Very Metal-poor Stars in the Galactic Halo from the HESP-GOMPA Survey 
    Bandyopadhyay, A; Sivarani, T; Beers, Timothy C; Susmitha, A; Nayak, Prasanta K; Pandey, Jeewan C (American Astronomical Society, 2022-10-01)
    We present a study on the detailed elemental abundances of newly identified, bright, very metal-poor stars with the detection of lithium, initially observed as part of the SDSS/MARVELS pre-survey. These stars were selected ...
  • Making Good Use of Bad Weather: Finding Extremely Metal-Poor Stars in the Clouds 
    Placco, V. M; Beers, T. C; Rossi, S; Kennedy, C; Christlieb, N; Lee, Y. S; Sivarani, T (Astronomical Society of the Pacific, 2012-12)
    Current results are presented for a new survey effort to search for Extremely Metal-Poor (EMP) and Carbon Enhanced Metal-Poor (CEMP) stars from the Hamburg / ESO objective-prism survey (HES). These stars are important ...
  • MARVELS-1b: A Short-period, Brown Dwarf Desert Candidate from the SDSS-III Marvels Planet Search 
    Lee, B. L; Ge, J; Fleming, S. W; Stassun, K. G; Gaudi, B. S; Barnes, R; Mahadevan, S; Eastman, J. D; Wright, J; Siverd, R. J; Gary, B; Ghezzi, L; Laws, C; Wisniewski, J. P; Porto de Mello, G. F; Ogando, R. L. C; Maia, M. A. G; Nicolaci da Costa, L; Sivarani, T; Pepper, J; Cuong Nguyen, D; Hebb, L; De Lee, N; Wang, J; Wan, X; Chang, L; Groot, J; Varosi, F; Hearty, F; Hanna, K; van Eyken, J. C; Kane, S. R; Agol, E; Bizyaev, D; Bochanski, J. J; Brewington, H; Chen, Z; Costello, E; Dou, L; Eisenstein, D. J; Fletcher, A; Ford, E. B; Guo, P; Holtzman, J. A; Jiang, P; French Leger, R; Liu, J; Long, D. C; Malanushenko, E; Malanushenko, V; Malik, M; Oravetz, D; Pan, K; Rohan, P; Schneider, D. P; Shelden, A; Snedden, S. A; Simmons, A; Weaver, B. A; Weinberg, D. H; Xie, J (IOP Publishing, 2011-02)
    We present a new short-period brown dwarf (BD) candidate around the star TYC 1240-00945-1. This candidate was discovered in the first year of the Multi-object APO Radial Velocity Exoplanets Large-area Survey (MARVELS), ...
  • The metal-poor end of the Spite plateau I. Stellar parameters, metallicities, and lithium abundances 
    Sbordone, L; Bonifacio, P; Caffau, E; Ludwig, H. -G; Behara, N. T; González Hernández, J. I; Steffen, M; Cayrel, R; Freytag, B; Van’t Veer, C; Molaro, P; Plez, B; Sivarani, T; Spite, M; Spite, F; Beers, T. C; Christlieb, N; François, P; Hill, V (EDP Sciences, 2010-11)
    Context. The primordial nature of the Spite plateau is at odds with the WMAP satellite measurements, implying a primordial Li production at least three times higher than observed. It has also been suggested that A(Li) might ...
  • The metal-poor end of the Spite plateau. II. Chemical and dynamical investigation 
    Pinto, A. M. Matas; Spite, M; Caffau, E; Bonifacio, P; Sbordone, L; Sivarani, T; Steffen, M; François, P; Di Matteo, P (EDP Sciences, 2021-10)
    Context. The study of old, metal-poor stars deepens our knowledge on the early stages of the universe. In particular, the study of these stars gives us a valuable insight into the masses of the first massive stars and their ...
  • The metal–poor end of the Spite plateau 
    Sbordone, L; Bonifacio, P; Caffau, E; Ludwig, H. -G; Behara, N; Gonzalez-Hernandez, J. I; Steffen, M; Cayrel, R; Freytag, B; Van't Veer, C; Molaro, P; Plez, B; Sivarani, T; Spite, M; Spite, F; Beers, T. C; Christlieb, N; François, P; Hill, V (Cambridge University Press, 2010-03)
    We present the largest sample available to date of lithium abundances in extremely metal poor (EMP) Halo dwarfs. Four Teff estimators are used, including IRFM and Hα wings fitting against 3D hydrodynamical synthetic ...
  • The metal–poor end of the Spite plateau: gravity sensitivity of the Hα wings fitting. 
    Sbordone, L; Bonifacio, P; Caffau, E; Ludwig, H. -G; Behara, N; Gonzalez-Hernandez, J. I; Steffen, M; Cayrel, R; Freytag, B; Van't Veer, C; Molaro, P; Plez, B; Sivarani, T; Spite, M; Spite, F; Beers, T. C; Christlieb, N; François, P; Hill, V (Cambridge University Press, 2010-04)
    We recently presented (Sbordone et al., 2009a) the largest sample to date of lithium abundances in extremely metal-poor (EMP) Halo dwarf and Turn-Off (TO) stars. One of the most crucial aspects in estimating Li abundances ...
  • The Milky Way Tomography with SDSS. III. Stellar Kinematics 
    Bond, N. A; Ivezić, Z; Sesar, B; Jurić, M; Munn, J. A; Kowalski, A; Loebman, S; Roškar, R; Beers, T. C; Dalcanton, J; Rockosi, C. M; Yanny, B; Newberg, H. J; Prieto, C. A; Wilhelm, R; Lee, Y. S; Sivarani, T; Majewski, S. R; Norris, J. E; Bailer-Jones, C. A. L; Fiorentin, P. R; Schlegel, D; Uomoto, A; Lupton, R. H; Knapp, G. R; Gunn, J. E; Covey, K. R; Smith, J. A; Miknaitis, G; Doi, M; Tanaka, M; Fukugita, M; Kent, S; Finkbeiner, D; Quinn, T. R; Hawley, S; Anderson, S; Kiuchi, F; Chen, A; Bushong, J; Sohi, H; Haggard, D; Kimball, A; McGurk, R; Barentine, J; Brewington, H; Harvanek, M; Kleinman, S; Krzesinski, J; Long, D; Nitta, A; Snedden, S; Lee, B; Pier, J. R; Harris, H; Brinkmann, J; Schneider, D. P (IOP Publishing, 2010-06-10)
    We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r < 20 and proper-motion measurements derived from Sloan Digital Sky Survey (SDSS) and POSS astrometry, including ~170,000 stars with ...
  • Modelling high resolution Echelle spectrographs for calibrations: Hanle Echelle spectrograph, a case study 
    Anantha, Ch; Jones, D; Sivarani, T (Springer, 2015-06)
    We present a modelling scheme that predicts the centroids of spectral line features for a high resolution Echelle spectrograph to a high accuracy. Towards this, a computing scheme is used, whereby any astronomical spectrograph ...
  • Near-IR Spectroscopy of CEMP Stars with SOAR/OSIRIS 
    Kennedy, C. R; Sivarani, T; Beers, T. C; Rossi, S; Placco, V. M; Johnson, J; Masseron, T (Cambridge University Press, 2010-03)
    We report on medium-resolution near-IR spectroscopy of a sample of over 60 Carbon- Enhanced Metal-Poor (CEMP) stars observed with SOAR/OSIRIS, selected from the HK survey of Beers and colleagues and the Hamburg/ESO Survey ...
  • A New Technique for Solar Imaging Spectro-polarimetry using Shack-Hartmann and Fabry-Perot 
    Placco, V. M; Beers, T. C; Rossi, S; Kennedy, C; Christlieb, N; Lee, Y. S; Sivarani, T (Astronomical Society of the Pacific, 2012-02)
    A new technique for solar imaging spectro-polarimetry is presented. Using the combination of a Shack-Hartmann (SH) and a Fabry-Pérot (FP) interferometer, high-cadence spectroscopic observations can be obtained at discrete ...
  • [O/Fe] Estimates for Carbon-enhanced Metal-poor Stars from Near-infrared Spectroscopy 
    Kennedy, C. R; Sivarani, T; Beers, T. C; Lee, Y. S; Placco, V. M; Rossi, S; Christlieb, N; Herwig, F; Plez, B (IOP Publishing, 2011-03)
    We report on oxygen abundances determined from medium-resolution near-infrared spectroscopy for a sample of 57 carbon-enhanced metal-poor (CEMP) stars selected from the Hamburg/ESO Survey. The majority of our program stars ...
  • Optical and NIR spectroscopy of cool CEMP stars to probe the nucleosynthesis in low-mass AGB binary system 
    Susmitha, A; Ojha, D. K; Sivarani, T; Ninan, J. P; Bandyopadhyay, A; Surya, Arun; Unni, Athira (Oxford University Press on behalf of Royal Astronomical Society, 2021-09)
    We present the abundance analyses of seven carbon enhanced metal-poor (CEMP) stars to understand the origin of carbon in them. We used high-resolution optical spectra to derive abundances of various elements. We also used ...
  • Optical observations and dust modelling of comet 156P/Russell-LINEAR 
    Aravind, K; Halder, Prithish; Ganesh, Shashikiran; Sahu, D. K; Serra-Ricart, Miquel; Chambo, Jose J; Angchuk, D; Sivarani, T (Elsevier B.V., 2022-09-01)
    Comet 156P/Russell-LINEAR is a short period Jupiter family comet with an orbital period of 6.44 years. The results from spectroscopic, photometric, polarimetric observations and dust modelling studies are presented here. ...
  • Optical spectroscopy of SN1998S 
    Anupama, G. C; Pandey, G; Sivarani, T (Astronomical Society of India, 2000)
  • Oxygen abundances of carbon-enhanced stellar population in the halo 
    Susmitha, A; Sivarani, T; Ojha, D. K; Ninan, Joe P; Bandyopadhyay, A; Surya, A; Athira, U (Springer, 2020-12)
    The large fraction of carbon-enhanced metal-poor (CEMP) stars at lower metallicities makes them an interesting class of objects to be probed further in greater detail. They show different abundance patterns of neutron-capture ...
  • 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 ...
  • Possibilities of identifying members from Milky Way satellite galaxies using unsupervised machine learning algorithms 
    Divakar, Devika K; Saraf, Pallavi; Sivarani, T; Doddamani, Vijayakumar H (Indian Academy of Sciences, 2024-06)
    A detailed study of stellar populations in Milky Way (MW) satellite galaxies remains an observational challenge due to their faintness and fewer spectroscopically confirmed member stars. We use unsupervised machine learning ...
  • Properties and Occurrence Rates for Kepler Exoplanet Candidates as a Function of Host Star Metallicity from the DR25 Catalog 
    Narang, Mayank; Manoj, P; Furlan, E; Mordasini, C; Henning, Thomas; Mathew, Blesson; Banyal, R. K; Sivarani, T (IOP Publishing, 2018-11)
    Correlations between the occurrence rate of exoplanets and their host star properties provide important clues about the planet formation process. We studied the dependence of the observed properties of exoplanets (radius, ...
  • Recovering simulated planet and disk signals using SCALES aperture masking 
    Lacha, Mackenzie R; Sallum, Steph; Banyal, R. K; Batalha, Natalie; Blake, Geoff; Brandt, Tim; Briesemeister, Zackery; Desai, Aditi; Eisner, Josh; Fong, Wen-fai; Greene, Tom; Honda, Mitsuhiko; Kain, Isabel; Kilpatrick, Charlie; Kleer, Katherine de; Liu, Michael; Macintosh, Bruce; Martinez, Raquel; Mawet, Dimitri; Miles, Brittany; Morley, Caroline; Pater, Imke de; Powell, Diana; Sheehan, Patrick; Skemer, Andrew; Spilker, Justin; Stelter, Deno; Stone, Jordan; Surya, Arun; Sivarani, T; Wagner, Kevin; Zhou, Yifan (SPIE - The International Society for Optical Engineering, 2023-10)
    The Slicer Combined with Array of Lenslets for Exoplanet Spectroscopy (SCALES) instrument is a lenslet-based integral field spectrograph that will operate at 2 to 5 microns, imaging and characterizing colder (and thus ...

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