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Browsing by Author "Sengupta, S"

Browsing by Author "Sengupta, S"

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  • A Newtonian interpretation of the parameter "a" associated with the Kerr metric 
    Sengupta, S (World Scientific Publishers, 1996-06)
    The parameter "a" associated with the Kerr metric has been used to determine the rotationally induced quadrapole electric field outside a rotating massive object with external dipole magnetic field. A comparison of the ...
  • Observation of R-Band Variability of L Dwarfs 
    Maiti, M; Sengupta, S; Parihar, P. S; Anupama, G. C (University of Chicago Press, 2005-02)
    We report, for the first time, photometric variability of L dwarfs in the R band. Out of three L1 dwarfs (2MASS 1300+19, 2MASS 1439+19, and 2MASS 1658+70) observed, we have detected R-band variability in 2MASS 1300+19 and ...
  • Observed polarization of brown dwarfs suggests low surface gravity 
    Sengupta, S; Marley, M. S (IOP Publishing, 2010-10-20)
    Light scattering by atmospheric dust particles is responsible for the polarization observed in some L dwarfs. Whether this polarization arises from an inhomogeneous distribution of dust across the disk or an oblate shape ...
  • Optical linear polarization in ultra cool dwarfs: A tool to probe dust in the ultra cool dwarf atmospheres 
    Tata, R; Martin, E. L; Sengupta, S; Phan-Bao, N; Zapatero Osorio, M. R; Bouy, H (European Space Agency, 2009-12)
    Aims.Recent studies have detected linear polarization in L dwarfs in the optical I band. Theoretical models have been developed to explain this polarization. These models predict higher polarization at shorter wavelengths. ...
  • Optical Transmission Spectra of Hot Jupiters: Effects of Scattering 
    Sengupta, S; Chakrabarty, Aritra; Tinetti, Giovanna (IOP Publishing, 2020-02-01)
    We present new grids of transmission spectra for hot Jupiters by solving the multiple-scattering radiative transfer equations with non-zero scattering albedo instead of using the Beer–Bouguer–Lambert law for the change in ...
  • Polarimetric detection of exoplanets transiting T and L brown dwarfs 
    Sengupta, S (IOP Publishing, 2016-10)
    While scattering of light by atoms and molecules yields large amounts of polarization at the B-band of both T and L dwarfs, scattering by dust grains in the cloudy atmosphere of L dwarfs gives rise to significant polarization ...
  • Polarization of L Dwarfs by Dust Scattering 
    Sengupta, S; Kwok, S (The American Astronomical Society, 2005-06)
    The degree of polarization in L dwarfs of spectral types L0-L6 resulting from dust scattering in a rotation-induced oblate photosphere is calculated. Assuming that forsterite is the main condensate, we derive the atmospheric ...
  • Polarization of Rotationally Oblate Self-luminous Exoplanets with Anisotropic Atmospheres 
    Chakrabarty, Aritra; Sengupta, S; Marley, Mark S (American Astronomical Society, 2022-03-01)
    The young self-luminous giant exoplanets are expected to be oblate in shape, owing to the high rotational speeds observed for some objects. Similar to the case of brown dwarfs, the thermal emission from these planets should ...
  • Polarization of Starlight by Unresolved and Oblate Extra-solar Planet in Elliptical Orbit 
    Sengupta, S; Maiti, M (University of Chicago Press, 2006-03)
    We calculate the degree of linear polarization of radiation from stars having planets that may not be resolved spatially. We assume single scattering by water and silicate particulates in the planetary atmosphere. The ...
  • Polarization of Trappist-1 by the Transit of Its Planets 
    Sengupta, S (IOP Publishing, 2018-07-01)
    Being the first, and currently the only, multiple planet hosting dwarf star that is sufficiently cool to form condensate clouds in its atmosphere, Trappist-1 provides a unique opportunity to test the efficiency of image ...
  • Precise photometric transit follow-up observations of five close-in exoplanets: update on their physical properties 
    Aritra Chakrabarty; Sengupta, S (IOP Publishing, 2019-07)
    We report the results of the high-precision photometric follow-up observations of five transiting hot Jupiters, WASP-33b, WASP-50b, WASP-12b, HATS-18b, and HAT-P-36b. The observations are made from the 2 m Himalayan Chandra ...
  • Probing Dust in the Atmosphere of Brown Dwarfs through Polarization 
    Sengupta, S; Krishan, V (The American Astronomical Society, 2001-11)
    The theoretical analysis and observational evidence indicate that a brown dwarf with an effective temperature greater than 1300 K would have a dust cloud in its atmosphere. In this Letter, we show that dust scattering ...
  • Probing the physical properties of directly imaged gas giant exoplanets through polarization 
    Marley, Mark S; Sengupta, S (Wiley-Blackwell, 2011-11)
    It is becoming clear that the atmospheres of the young, self-luminous extrasolar gi- ant planets imaged to date are dusty. Planets with dusty atmospheres may exhibit detectable amounts of linear polarization in the ...
  • Resonance Line Polarization in a Moving Medium - Solution in the Comoving Frame with Complete Frequency Redistribution 
    Sengupta, S (Royal Astronomical Society, 1993-12-01)
    We study the effect of differential radial velocity on the distribution of line intensities and line polarization along the line of sight of an extended stellar atmosphere stratified in parallel planes. The main purpose ...
  • Resonance-Line Polarization in Expanding Spherical Atmospheres - Solution in the Comoving Frame 
    Sengupta, S (Royal Astronomical Society, 1994-07)
    The effect of differential radial velocity in the distribution of line intensities and line polarization along the line of sight of an extended stellar atmosphere has been studied. The medium is assumed to be inhomogeneous, ...
  • The Search for another earth 
    Sengupta, S (Indian Academy of Sciences, 2016-07)
    Is there life anywhere else in the vast cosmos?Are there planets similar to the Earth? For centuries,these questions baffled curious minds. Eithera positive or negative answer, if found oneday, would carry a deep philosophical ...
  • The search for another earth - Part II 
    Sengupta, S (Indian Academy of Sciences, 2016-10)
    In the first part, we discussed the various methods for thedetection of planets outside the solar system known as theexoplanets. In this part, we will describe various kinds ofexoplanets. The habitable planets discovered ...
  • A Search for Polarized Thermal Emission from Directly Imaged Exoplanets and Brown Dwarf Companions to Nearby Stars 
    Jensen-Clem, R; Millar-Blanchaer, M. A; van Holstein, R. G; Mawet, Dimitri; Graham, J; Sengupta, S; Marley, M. S; Snik, Frans; Vigan, A; Hinkley, S; de Boer, Jos; Girard, J. H; De Rosa, R. J; Bowler, B. P; Wiktorowicz, S. J; Perrin, M. D; Crepp, J. R; Macintosh, B (IOP Publishing, 2020-12)
    Aerosols in the atmospheres of cloudy gas giant exoplanets and brown dwarfs scatter and polarize these objects' thermal emission. If such an object has an oblate shape or nonuniform cloud distribution, the net degree of ...
  • Spectro-Polarimetry of Self-Luminous Extrasolar Planets 
    Sengupta, S (Indian Academy of Sciences, 2013-06)
    Planets which are old and close to their parent stars are considered as reflecting planets because their intrinsic temperature is extremely low but they are heated strongly by the impinging stellar radiation and hence ...
  • The Sunyaev-Zel Effect by Multiple Scattering: Numerical solution of the transfer equations 
    Sengupta, S (World Scientific Publishing Company, 2004-05-10)
    The radiative transfer equations for multiple inverse Compton scattering of the Cosmic Microwave Background Radiation (CMBR) by the hot intra-cluster electrons are solved numerically. The spherical isothermal and inhomogeneous ...

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