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Browsing by Author "Sivarani, T"

Browsing by Author "Sivarani, T"

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  • [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 ...
  • A road map for the generation of a near-infrared guide star catalog for thirty meter telescope observations 
    Subramanian, S; Subramaniam, A; Sivarani, T; Simard, Luc; Anupama, G. C; Gillies, Kim; Ramaprakash, A. N; Reddy, B. E (Indian Academy of Sciences, 2016-09)
    The near-infrared instruments in the upcoming Thirty Meter Telescope (TMT) will be assisted by a multi conjugate Adaptive Optics (AO) system. For the efficient operation of the AO system, during observations, a near-infrared ...
  • SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way, and Extra-Solar Planetary Systems 
    Eisenstein, D. J and 243 coauthors; Sivarani, T (IOP Publishing, 2011-09)
    Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of ...
  • A Search for Unrecognized Carbon-Enhanced Metal-Poor Stars 
    Placco, V. M; Kennedy, C. R; Rossi, S; Beers, T. C; Christlieb, N; Sivarani, T (Cambridge University Press, 2010-03)
    We have developed a new procedure to search for Carbon-Enhanced Metal-Poor (CEMP) stars from the Hamburg/ESO (HES) prism-survey plates. This method uses an extended line index for the CH G-band, which we demonstrate to ...
  • A search for unrecognized carbon-enhanced metal-poor stars in the galaxy 
    Placco, V. M; Kennedy, C. R; Rossi, S; Beers, T. C; Lee, Y. S; Christlieb, N; Sivarani, T; Reimers, D; Wisotzki, L (Institute of Physics, 2010-03)
    We have developed a new procedure to search for carbon-enhanced metal-poor (CEMP) stars from the Hamburg/ESO (HES) prism-survey plates. This method employs an extended line index for the CH G band, which we demonstrate to ...
  • Searches for Metal-poor Stars from the Hamburg/ESO Survey Using the CH G Band 
    Placco, V. M; Kennedy, C. R; Beers, T. C; Christlieb, N; Rossi, S; Sivarani, T; Lee, Young Sun; Reimers, D; Wisotzki, L (IOP Publishing, 2011-12)
    We describe a new method to search for metal-poor candidates from the Hamburg/ESO objective-prism survey (HES) based on identifying stars with apparently strong CH G-band strengths for their colors. The hypothesis we exploit ...
  • The SEGUE Stellar Parameter Pipeline. IV. Validation with an Extended Sample of Galactic Globular and Open Clusters 
    Smolinski, J. P; Lee, Y. S; Beers, T. C; An, D; Bickerton, S. J; Johnson, J. A; Loomis, C. P; Rockosi, C. M; Sivarani, T; Yanny, B (IOP Publishing, 2011-03)
    Spectroscopic and photometric data for likely member stars of five Galactic globular clusters (M3, M53, M71, M92, and NGC 5053) and three open clusters (M35, NGC 2158, and NGC 6791) are processed by the current version of ...
  • The SEGUE Stellar Parameter Pipeline. V. Estimation of Alpha-element Abundance Ratios from Low-resolution SDSS/SEGUE Stellar Spectra 
    Lee, Y. S; Beers, T. C; Prieto, C. A; Lai, D. K; Rockosi, C. M; Morrison, H. L; Johnson, J. A; An, D; Sivarani, T; Yanny, B (IOP Publishing, 2011-03)
    We present a method for the determination of [α/Fe] ratios from low-resolution (R = 2000) SDSS/SEGUE stellar spectra. By means of a star-by-star comparison with degraded spectra from the ELODIE spectral library and with a ...
  • Simulating medium-spectral-resolution exoplanet characterization with SCALES angular/reference differential imaging 
    Desai, Aditi; Sallum, Stephanie E; Banyal, R. K; Batalha, Natalie; Batalha, Natasha; Blake, Geoff; Brandt, Tim; Briesemeister, Zack; Kleer, Katherine de; Pater, Imke de; Eisner, Josh; Fong, Wen-fai; Greene, Tom; Honda, Mitsuhiko; Kain, Isabel; Kilpatrick, Charlie; Lach, Mackenzie; Liu, Mike; Macintosh, Bruce; Martinez, Raquel A; Mawet, Dimitri; Miles, Brittany; Morley, Caroline; Powell, Diana; Sheehan, Patrick; Skemer, Andrew J; Spilker, Justin; Stelter, R. Deno; Stone, Jordan; Surya, Arun; Sivarani, T; Wagner, Kevin; Zhou, Yifan (SPIE-The International Society for Optical Engineering, 2023-10)
    SCALES (Slicer Combined with Array of Lenslets for Exoplanet Spectroscopy) is a 2 - 5 micron high-contrast lenslet-based integral field spectrograph (IFS) designed to characterize exoplanets and their atmospheres. The SCALES ...
  • The slicer combined with array of lenslets for exoplanet spectroscopy (SCALES): driving science cases and expected outcomes 
    Sallum, Steph; Skemer, Andrew; Stelter, Deno; Banyal, R. K; Batalha, Natalie; Batalha, Natasha; Blake, Geoff; Brandt, Tim; Briesemeister, Zack; Kleer, Katherine de; Pater, Imke de; Desai, Aditi; Eisner, Josh; Fong, Wen-fai; Greene, Tom; Honda, Mitsuhiko; Jensen-Clem, Rebecca; Kain, Isabel; Kilpatrick, Charlie; Kupke, Renate; Lach, Mackenzie; Liu, Michael C; Macintosh, Bruce; Martinez, Raquel A; Mawet, Dimitri; Miles, Brittany; Morley, Caroline; Powell, Diana; Sethuram, Ramya; Sheehan, Patrick; Spilker, Justin; Stone, Jordan; Surya, Arun; Sivarani, T; Unni, Athira; Wagner, Kevin; Zhou, Yifan (SPIE-The International Society for Optical Engineering, 2023-10)
    The Slicer Combined with Array of Lenslets for Exoplanet Spectroscopy (SCALES) is a 2 − 5 µm, high-contrast integral field spectrograph (IFS) currently being built for Keck Observatory. With both low (R ≲ 250) and medium ...
  • Spectroscopic observations of first ISOGAL sources 
    Ojha, D. K; Sivarani, T; Parthasarathy, M; Omont, A; Ganesh, S; Simon, G (Astronomical Society of India, 2000)
    Infrared Space Observatory Galactic (ISOGAL) survey at 7 and 15 μm of ~ 22 deg2 of the inner galactic disk and bulge, has detected several hundred thousand sources. Combining ISOGAL survey with I, J, H, Ks data of DENIS ...
  • Spectroscopic study of stars with dusty disks 
    Sivarani, T; Parthasarathy, M (2004)
    We have selected several stars with far-IR (IRAS)fluxes indicating the presence of circumstellar dust shells and disks. In this paper we present an analysis of the spectra of these stars. In several of these stars we find ...

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