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Browsing by Author "Bhatt, N"

Browsing by Author "Bhatt, N"

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  • Computer Network - based data acquisition and control system for the imaging element of the TACTIC array 
    Kanda, A; Koul, R; Bhatt, N; Kaul, S. R (Astronomical Society of India, 1999)
    An interrupt-driven distributed Data AcQuisition and Control System (DAQCS) has been developed for the Imaging Element of the 4-element gamma-ray telescope array, TACTIC. A network of PCs, running the QNX RTOS, have been ...
  • Drive control system for the TACTIC γ-ray telescope 
    Tickoo, A. K; Koul, R; Kaul, S. K; Kaul, I. K; Bhat, C. L; Bhatt, N (Astronomical Society of India, 1999)
    We present here some salient features of the hardware and software aspects of the 2-axes drive system developed for the TACTIC γ-ray telescope array. A test-report of its performance is also presented
  • The Effect of Non-thermal Protons on the High Energy Spectra of Black Hole Binaries 
    Bhattacharyya, S; Bhatt, N; Misra, R; Kaul, C. L (Astronomical Society of India, 2003)
    We investigate here the effect on the emitted spectrum of a black hole binary due to the presence of accelerated protons in the inner region of the accretion disk. Our study shows that e-e+ pairs and high energy -rays ...
  • Energy Sensitive Search for Pulsed Photons from Crab Pulsar using the TACTIC Imaging Element 
    Rannot, R. C; Yadav, K. K; Dhar, V. K; Tickoo, A. K; Bhatt, N; Bhattacharyya, S; Chandra, P; Goyal, H. C; Kaul, C. L; Kaul, R. K; Kothari, M; Kotwal, S; Koul, R; Sahayanathan, S; Sapru, M. L; Sharma, M; Venugopal, K; Bhat, C. L (Astronomical Society of India, 2003)
    The Imaging Element (IE) of the 4-element TACTIC array of atmospheric Cherenkov telescopes is in operation at Mt. Abu Rajasthan, in Western India. We have successfully detected a steady signal from the Crab Nebula at a ...
  • Long-Term Monitoring of Blazar PKS 0208-512: A Change of γ-Ray Baseline Activity from EGRET to Fermi Era 
    Ammenadka, Krishna Mohana; Bhattacharya, Debbijoy; Bhattacharyya, Subir; Bhatt, N; Stalin, C. S (Multidisciplinary Digital Publishing Institute, 2022-10)
    The blazar PKS 0208-512 was in the lowest 𝛾 -ray brightness state during the initial 10 years of observations with the Fermi Gamma-ray Space Telescope (Fermi), which was an order of magnitude lower than its flux state ...
  • Multinode data acquisition and control system for the Vertex Elements of the TACTIC telescope array 
    Yadav, K. K; Bhatt, N; Kaul, S. R; Koul, R (Astronomical Society of India, 2001)
    An interrupt based multinode data acquisition and control system has been developed for the three Vertex Elements of the TACTIC telescope array. The paper describes the salient design features of the hardware and software ...
  • Multiwavelength monitoring of NGC 1275 over a decade: evidence of a shift in synchrotron peak frequency and long-term multiband flux increase 
    Gulati, Sanna; Bhattacharya, Debbijoy; Bhattacharyya, Subir; Bhatt, N; Stalin, C. S; Agrawal, V. K (Oxford University Press on behalf of the Royal Astronomical Society, 2021-05)
    We carried out a detailed study of the temporal and broad-band spectral behaviour of one of the brightest misaligned active galaxies in γ-rays, NGC 1275, utilizing 11 years of Fermi data and the available Swift and AstroSat ...
  • Multiwavelength study of different flaring and low-activity states of blazar 4C+21.35 
    Bhattacharya, D; Krishna Mohana, A; Bhattacharyya, S; Bhatt, N; Stalin, C. S (Oxford University Press on behalf of the Royal Astronomical Society, 2021-01)
    Blazars, a class of active galactic nuclei, emit over the entire accessible electromagnetic spectrum and modelling of their broad-band spectral energy distribution (SED) is the key to constrain the underlying emission ...
  • Observations with the High Altitude GAmma Ray (HAGAR) telescope array in the Indian Himalayas 
    Britto, R. J; Acharya, B. S; Anupama, G. C; Bhatt, N; Bhattacharjee, P; Bhattacharya, S. S; Chitnis, V. R; Cowsik, R; Dorji, N; Duhan, S. K; Gothe, K. S; Kamath, P. U; Koul, R; Mahesh, P. K; Mitra, A; Nagesh, B. K; Parmar, N. K; Prabhu, T. P; Rannot, R. C; Rao, S. K; Saha, L; Saleem, F; Saxena, A. K; Sharma, S. K; Shukla, A; Singh, B. B; Srinivasan, R; Srinivasulu, G; Sudersanan, P. V; Tickoo, A. K; Tsewang, D; Upadhya, S; Vishwanath, P. R; Yadav, K. K (French Society of Astronomy and Astrophysics, 2010-12)
    For several decades, it was thought that astrophysical sources emit high energy photons within the energy range of the gamma-ray region of the lectromagnetic spectrum also. These photons originate from interactions of high ...
  • Observations with the High Altitude GAmma-Ray (HAGAR) telescope array in the Indian Himalayas 
    Britto, R. J; Acharya, B. S; Anupama, G. C; Bhatt, N; Bhattacharjee, P; Bhattacharya, S; Chitnis, V. R; Cowsik, R; Dorji, N; Duhan, S. K; Gothe, K. S; Kamath, P. U; Koul, R; Manoharan, J; Mahesh, P. K; Mitra, A; Nagesh, B. K; Parmar, N. K; Prabhu, T. P; Rannot, R. C; Rao, S. K; Saha, L; Saleem, F; Saxena, A. K; Sharma, S. K; Shukla, A; Singh, B. B; Srinivasan, R; Srinivasulu, G; Sudersanan, P. V; Tickoo, A. K; Tsewang, D; Upadhya, S. S; Vishwanath, P. R; Yadav, K. K (Copernicus Publications, 2011-11)
    The High Altitude GAmma-Ray (HAGAR) array is a wavefront sampling array of 7 telescopes, set-up at Hanle, at 4270 m amsl, in the Ladakh region of the Himalayas (Northern India). It constitutes the first phase of the HImalayan ...
  • Orbital Evolution of the Binary X-ray Pulsar Her X-1 
    Bhatt, N; Paul, B; Koul, C. L (Astronomical Society of India, 2003)
    We report the discovery of a break in the orbital period evolution of Her X-1, coincident with a recent anomalous low state.
  • Recent observations of lES2344+514 and PSR 0355+54 with TACTIC Imaging Element 
    Tickoo, A. K; Dhar, V. K; Yadav, K. K; Rannot, R. C; Bhattacharyya, S; Chandra, P; Goyal, H. C; Kaul, C. L; Kaul, R. K; Kothari, M; Kotwal, S; Koul, R; Sahayanathan, S; Sapru, M. L; Sharma, M; Venugopal, K; Bhatt, N; Bhatt, C. L (Astronomical Society of India, 2002-09)
    The TACTIC Imaging Element has observed the active galaxy 1ES 2344+514 and the pulsar PSR 0355+54 during Oct-Nov, 2001. Analysis of the recorded events, collected for a period of 70 hours on both these sources reveals ...
  • Recent results on crab nebula and Mkn-421 observations with TACTIC imaging element 
    Bhatt, N; Agarwal, N. K; Bhat, C. K; Bhattacharaya, S; Charagi, S. K; Chandra, P; Chauhan, N; Dhar, V. K; Goyal, A; Goyal, H. C; Kamath, K; Kaul, C. L; Kaul, I. K; Kaul, R. K; Kaul, S. K; Kaul, S. R; Sharma, M; Kothari, M; Kotwal, S. V; Koul, D. K; Koul, M. K; Rannot, R. C; Razdan, A. K; Sahaynathan, S; Sapru, M. L; Satyabhama, N; Tickoo, A. K; Venugopal, K; Yadav, K. K; Bhat, C. L (Astronomical Society of India, 2002)
    The results of our recent observational campaigns on the Crab Nebula and Mkn-421, carried out with the 349-pixel Imaging Element of the TACTIC array, are presented alongwith the details of the data analysis. Analysis of ...
  • Search for pulsed Te V gamma- rays from Crab pulsar with the TACTIC Imaging gamma-ray Telescope 
    Rannot, R. C; Yadav, K. K; Dhar, V. K; Tickoo, A. K; Bhatt, N; Bhattacharyya, S; Chandra, P; Goyal, H. C; Kaul, C. L; Kaul, R. K; Kothari, M; Kotwal, S; Koul, R; Sahayanathan, S; Sapru, M. L; Sharma, M; Venugopal, K; Bhat, C. L (Astronomical Society of India, 2002-09)
    The TACTIC Imaging Element has observed Crab Nebula/pulsar for a total. of about 40 hours during Jan.- Mar. 2001. Preliminary results do not show any evidence of the 33 ms pulsations from the pulsar direction at an energy ...
  • Simulation and experimental studies of polarization properties of atmospheric Cerenkov pulses 
    Bhat, C. L; Rannot, R. C; Mohapatra, D. K; Gandhi, V. N; Tickoo, A. K; Kaul, R; Kaul, S. K; Kaul, S. R; Goyal, H. C; Bhatt, N (Astronomical Society of India, 1999)
    We present here preliminary results obtained form some simulation and experimental investigations on the polarization state of atmospheric Cerenkov events.
  • Status of the Himalayan Gamma-Ray Observatory (HIGRO) and observation with HAGAR at very high energies 
    Britto, R. J; Acharya, B. S; Anupama, G. C; Bhatt, N; Bhattacharjee, P; Bhattacharya, S; Chitnis, V. R; Cowsik, R; Dorji, N; Duhan, S. K; Gothe, K. S; Kamath, P. U; Koul, R; Mahesh, P. K; Manoharan, J; Mitra, A; Nagesh, B. K; Parmar, N. K; Prabhu, T. P; Rannot, R. C; Rao, S. K; Saha, L; Saleem, F; Saxena, A. K; Sharma, S. K; Shukla, A; Singh, B. B; Srinivasan, R; Srinivasulu, G; Sudersanan, P. V; Tickoo, A. K; Tsewang, D; Upadhya, S. S; Vishwanath, P. R; Yadav, K. K (French Society of Astronomy and Astrophysics, 2011-12)
    High Altitude GAmma Ray (HAGAR) telescope array, which is the first stage of HImalayan Gamma Ray Observatory (HIGRO), has been successfully installed at Hanle in Himalayas and has been collecting science data since September, ...
  • Towards absolute gain calibration of the TACTIC imaging element 
    Tickoo, A. K; Dhar, V. K; Venugopal, K; Yadav, K. K; Kaul, S. K; Koul, R; Kothari, M. K; Goyal, H. C; Chandra, P; Bhatt, N; Bhat, C. L (Astronomical Society of India, 2002)
    The imaging element of the 4-element TACTIC telescope array has been in operation at Mt. Abu since 1997, for carrying out detailed investigations of gamma-ray sources in the TeV energy range. In order to characterize the ...
  • Towards new analysis of Gamma-Ray sources at HImalayan Gamma-Ray Observatory (HIGRO) in northern India 
    Britto, R. J; Acharya, B. S; Anupama, G. C; Bhatt, N; Bhattacharjee, P; Bhattacharya, S; Chitnis, V. R; Cowsik, R; Dorji, N; Duhan, S. K; Gothe, K. S; Kamath, P. U; Koul, R; Mahesh, P. K; Mitra, A; Nagesh, B. K; Parmar, N. K; Prabhu, T. P; Rannot, R. C; Rao, S. K; Saha, L; Saleem, F; Saxena, A. K; Sharma, S. K; Shukla, A; Singh, B. B; Srinivasan, R; Srinivasulu, G; Sudersanan, P. V; Tickoo, A. K; Tsewang, D; Upadhya, S. S; Vishwanath, P. R; Yadav, K. K (French Society of Astronomy and Astrophysics, 2010-12)
    The High Altitude GAmma-Ray (HAGAR) array is a wavefront sampling array of 7 telescopes, set-up at Hanle, at 4270 m a.s.l., in the Ladakh region of the Himalayas (North India). It constitutes the first phase of the HImalayan ...
  • 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 ...

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