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Browsing by Author "Sreekumar, P"

Browsing by Author "Sreekumar, P"

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  • Multilayer Mirror Based High-Resolution Solar Soft X-Ray Spectrometer 
    Panini, S. S; Narendranath, S; Sreekumar, P; Sankarasubramanian, K (Frontiers Media S.A, 2021-07)
    Soft X-ray spectroscopy of the Sun is an important tool to understand the coronal dynamics and composition. The solar coronal X-ray spectrum below 1 keV is the least explored with high-resolution spectroscopy. Recent ...
  • Multilayer mirror-based soft x-ray polarimeter for astronomical observations 
    Panini, S. S; Sreekumar, P; Marshall, H. L; Narendranath, S; Nayak, M; Athiray, P. S (SPIE-The International Society for Optical Engineering, 2018-01)
    A simple design of a soft x-ray polarimeter using multilayer mirrors is presented. A multilayer mirror acts as a linear polarization analyzer for x-rays at incidence angles close to the Brewster angle. The instrument ...
  • Multiwavelength study of radio galaxy Pictor A: detection of western hotspot in far-UV and possible origin of high energy emissions 
    Gulati, Sanna; Bhattacharya, Debbijoy; Ramadevi, M. C; Stalin, C. S; Sreekumar, P (Oxford University Press on behalf of Royal Astronomical Society, 2023-05)
    A comprehensive study of the nucleus and western hotspot of Pictor A is carried out using AstroSat observations, 13 yr of Fermi, and archival Swift observations along with other published data. We report the first detection ...
  • New views of southern nearside lunar highland composition from the chandrayaan-1 x-ray spectrometer (C1XS) 
    Athiray, P. S; Narendranath, S; Sreekumar, P (2016-10)
    Lunar surface elemental abundances - Results from Chandrayaan-1 X-ray Spectrometer (C1XS) on-board Chandrayaan-1 and goals for the upcoming Chandrayaan-2 Large Area Soft X-ray Spectrometer (CLASS) experiment on-board ...
  • Processing electronics instrumentation for the low energy detector of Solar X-ray Spectrometer (SOXS) experiment 
    Umapathy, C. N; Sharma, M. R; Solanky, C; Kulkarni, R; Shah, A. B; Vadher, N. M; Jain, R; Jain, A. K; Sreekumar, P (Astronomical Society of India, 2001)
  • Proposed visible emission line space solar coronagraph 
    Singh, J; Prasad, B. R; Venkatakrishnan, P; Sankarasubramanian, K; Banerjee, D; Bayanna, R; Mathew, S; Murthy, J; Subramaniam, P; Ramesh, R; Kathiravan, S; Nagabhushana, S; Mahesh, P. K; Manoharan, P. K; Uddin, W; Sriram, S; Amit Kumar; Srivastava, N; Koteswara Rao; Nagendra, C. L; Chakraborty, P; Sriram, K. V; Venkateswaran, R; Krishnamurthy, T; Sreekumar, P; Sarma, K. S; Murthy, R; Navalgund, K. H; Samudraiah, D. R. M; Narayan Babu, P; Patra, A (Indian Academy of Sciences, 2011-01-25)
    The outer atmosphere of the sun – called the corona – has been observed during total solar eclipse for short periods (typically < 6 min), from as early as the eighteenth century. In the recent past, space-based instruments ...
  • Simulating charge transport to understand the spectral response of swept charge devices 
    Athiray, P. S; Sreekumar, P; Narendranath, S; Gow, J. P. D (EDP Sciences, 2015-11)
    Context. Swept Charge Devices (SCD) are novel X-ray detectors optimized for improved spectral performance without any demand for active cooling. The Chandrayaan-1 X-ray Spectrometer (C1XS) experiment onboard the Chandrayaan-1 ...
  • Soft x-ray imager using multilayer mirror optics for martian exospheric studies 
    Panini, S. S; Narendranath, S; Sreekumar, P; Athiray, P. S (2010-07)
    Planetary X ray measurements in the past have yielded valuable science in several areas such as the surface chemistry, polar auroras, magnetospheres and solar wind interaction with the exosphere. X-ray ...
  • SoLEXS - A low energy X-ray spectrometer for solar coronal studies 
    Sankarasubramanian, K; Ramadevi, M. C; Bug, M; Umapath, C. N; Seetha, S; Sreekumar, P; Kumar (Astronomical Society of India, 2011)
    A Solar Low-energy X-ray Spectrometer (SoLEXS), a high spectral resolution (≤ 250 eV at 5.9 keV) instrument with soft X-ray energy coverage (≤ 1.5 keV), is being proposed as an additional payload on-board Aditya-1. The ...
  • Spectral evolution of LMXB GX 349+2 
    Agrawal, V; Sreekumar, P (Astronomical Society of India, 2002-09)
    Z sources are the brightest low-mass X-ray binaries (LMXB) believed to contain magnetized neutron stars. They trace a '2' shaped track in theil X-ray colour-colour diagram. It is thought that the accretion rate increases ...
  • Study of type I X-ray bursts from 4U 1705-44 using IXAE and PCA data 
    Agrawal, V. K; Sreekumar, P; Seetha, S; Agrawal, P. C (Astronomical Society of India, 2001)
  • Thermal and temporal stability of W / B4C multilayer mirrors for space-based astronomical applications 
    Panini, S. S; Nayak, M; Gupta, Rajkumar; Pradhan, Paresh C.; Majhi, Arindam; Narendranath, S; Sreekumar, P (SPIE-Society of Photo-Optical Instrumentation Engineers, 2018-10)
    W  /  B4C multilayer (ML) mirrors with varying periodicities   (  d  )    =  1.6 to 5.4 nm are tested for rapid thermal and temporal stability, which are required for space-based x-ray telescopes for astronomy. The aging ...
  • Timing and spectral studies of the 1999 Outburst of 4U 1630-47 
    Abraham, L; Agrawal, V; Sreekumar, P; Seetha, S (Astronomical Society of India, 2001)
  • Ultraviolet imaging observations of three jellyfish galaxies: star formation suppression in the centre and ongoing star formation in stripped tails 
    George, K; Poggianti, B. M; Tomicic, N; Postma, J; Cote, P; Fritz, J; Ghosh, S. K; Gullieuszik, M; Hutchings, J. B; Moretti, A; Omizzolo, A; Radovich, M; Sreekumar, P; Subramaniam, A; Tandon, S. N; Vulcani, B (Oxford University Press on behalf of Royal Astronomical Society, 2023-02)
    Spiral galaxies undergo strong ram-pressure effects when they fall into the galaxy cluster potential. As a consequence, their gas is stripped to form extended tails within which star formation can happen, giving them the ...
  • Unusual long-term low-activity states of EGRET blazars in the Fermi era 
    Bhattacharya, Debbijoy; Mohana A, K; Gulati, S; Bhattacharyya, Subir; Bhatt, N; Sreekumar, P; Stalin, C. S (Oxford University Press on behalf of the Royal Astronomical Society, 2017-11)
    We examine the long-term (∼10 years) γ-ray variability of blazars observed by the Energetic Gamma Ray Experiment Telescope (EGRET) and Fermi and find that 10 EGRET-detected flat-spectrum radio quasars (FSRQs) were not ...
  • UVIT observations of the star-forming ring in NGC 7252: Evidence of possible AGN feedback suppressing central star formation 
    George, K; Joseph, P; Mondal, Chayan; Devaraj, A; Subramaniam, A; Stalin, C. S; Cote, P; Ghosh, S. K; Hutchings, J. B; Mohan, Rekhesh; Postma, J; Sankarasubramanian, K; Sreekumar, P; Tandon, S. N (EDP Sciences, 2018-05)
    Context. Some post-merger galaxies are known to undergo a starburst phase that quickly depletes the gas reservoir and turns it into a red-sequence galaxy, though the details are still unclear. Aims. Here we explore the ...
  • UVIT view of Centaurus A: a detailed study on positive AGN feedback 
    Joseph, P; Sreekumar, P; Stalin, C. S; Paul, K. T; Mondal, Chayan; George, Koshy; Mathew, Blesson (Oxford University Press on behalf of Royal Astronomical Society, 2022-10)
    Supermassive black holes at the centre of active galactic nuclei (AGNs) produce relativistic jets that can affect the star formation characteristics of the AGN hosts. Observations in the ultraviolet (UV) band can provide ...
  • UVIT view of ram-pressure stripping in action: Star formation in the stripped gas of the GASP jellyfish galaxy JO201 in Abell 85 
    George, K; Poggianti, B. M; Gullieuszik, M; Fasano, G; Bellhouse, C; Postma, J; Moretti, A; Jaffe, Y; Vulcani, B; Bettoni, D; Fritz, J; Cote, P; Ghosh, S. K; Hutchings, J. B; Mohan, Rekhesh; Sreekumar, P; Stalin, C. S; Subramaniam, A; Tandon, S. N (Oxford University Press on behalf of the Royal Astronomical Society, 2018-09)
    Jellyfish are cluster galaxies that experience strong ram-pressure effects that strip their gas. Their Hα images reveal ionized gas tails up to 100 kpc, which could be hosting ongoing star formation. Here, we report the ...

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