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Browsing by Subject "Methods: data analysis"

Browsing by Subject "Methods: data analysis"

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  • A butterfly diagram and carrington maps for century-long Ca II K spectroheliograms from the Kodaikanal Observatory 
    Chatterjee, Subhamoy; Banerjee, D; Ravindra, B (IOP Publishing, 2016-08-10)
    The century-long (1907–2007) Ca II K spectroheliograms from the Kodaikanal Solar Observatory (KSO) are calibrated, processed, and analyzed to follow the evolution of the bright on-disc structures called plages, possible ...
  • Carbon-Enhanced Metal-Poor Stars in SDSS/Segue. I. Carbon Abundance Estimation and Frequency of CEMP Star 
    Lee, Y. S; Beers, T. C; Masseron, T; Plez, B; Rockosi, C. M; Sobeck, J; Yanny, B; Lucatello, S; Sivarani, T; Placco, V. M; Carollo, D (IOP Publishing, 2013-11)
    We describe a method for the determination of stellar [C/Fe] abundance ratios using low-resolution (R = 2000) stellar spectra from the Sloan Digital Sky Survey (SDSS) and its Galactic sub-survey, the Sloan Extension for ...
  • Carbon-enhanced Metal-poor Stars in the Inner and Outer Halo Components of the Milky Way 
    Carollo, D; Beers, T. C; Bovy, Jo; Sivarani, T; Norris, J. E; Freeman, K. C; Aoki, W; Lee, Young Sun; Kennedy, C. R (IOP Publishing, 2012-01-10)
    Carbon-enhanced metal-poor (CEMP) stars in the halo components of the Milky Way are explored, based on accurate determinations of the carbon-to-iron ([C/Fe]) abundance ratios and kinematic quantities for over 30,000 ...
  • Data analysis method for the search of point sources of gamma rays with the HAGAR telescope array 
    Britto, R. J; Acharya, B. S; Anupama, G. C; Bhattacharjee, P; Chitnis, V. R; Cowsik, R; Dorji, N; Duhan, S. K; Gothe, K. S; Kamath, P. U; Mahesh, P. K; Manoharan, J; Nagesh, B. K; Parmar, N. K; Prabhu, T. P; 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; Tsewang, D; Upadhya, S. S; Vishwanath, P. R (French Society of Astronomy and Astrophysics, 2011-12)
    The High Altitude GAmma-Ray (HAGAR) experiment is the highest altitude atmospheric Cherenkov sampling array, set up at 4300 m amsl in the Himalayas (Northern India). It constitutes 7 telescopes, each one with seven 90 ...
  • Difference image analysis: extension to a spatially varying photometric scale factor and other considerations 
    Bramich, D. M; Horne, Keith; Albrow, M. D; Tsapras, Y; Snodgrass, C; Street, R. A; Hundertmark, M; Kains, N; Arellano Ferro, A; Figuera Jaimes, R; Giridhar, S (Oxford University Press on behalf of the Royal Astronomical Society, 2013-01-21)
    We present a general framework for matching the point-spread function (PSF), photometric scaling and sky background between two images, a subject which is commonly referred to as difference image analysis (DIA). We introduce ...
  • Disentangling the two sub-populations of early Herbig Be stars using VLT/X-shooter spectra 
    Shridharan, B; Mathew, B; Arun, R; Cysil, T. B; Subramaniam, A; Manoj, P; Maheswar, G; Sudheesh, T. P (EDP Sciences, 2023-11)
    Early Herbig Be (HBe) stars are massive, young stars accreting through the boundary layer mechanism. However, given the rapid (<2 Myr) evolution of early Herbig stars to the main-sequence phase, studying the evolution of ...
  • Emission line star catalogues post-Gaia DR3: A validation of Gaia DR3 data using the LAMOST OBA emission catalogue 
    Shridharan, B; Mathew, B; Bhattacharyya, S; Robin, T; Arun, R; Kartha, S. S; Manoj, P; Nidhi, S; Maheswar, G; Paul, K. T; Narang, M; Himanshu, T (EDP Sciences, 2022-12)
    Aims. Gaia Data Release 3 (DR3) and further releases have the potential to identify and categorise new emission-line stars in the Galaxy. We perform a comprehensive validation of astrophysical parameters from Gaia DR3 ...
  • An empirical relation to estimate host galaxy stellar light from AGN spectra 
    Jalan, Priyanka; Rakshit, Suvendu; Woo, Jong-Jak; Kotilainen, Jari; Stalin, C. S (Oxford University Press on behalf of Royal Astronomical Society, 2023-05)
    Measurement of black hole mass for low-z (z≤ 0.8) Active Galactic Nuclei (AGNs) is difficult due to the strong contribution from host galaxy stellar light necessitating detailed spectral decomposition to estimate the AGN ...
  • Fraction of broad absorption line quasars in different radio morphologies 
    Nair, A; Vivek, M (Oxford University Press on behalf of Royal Astronomical Society, 2022-04)
    In this study, we investigated the orientation model of Broad Absorption Line (BAL) quasars using a sample of sources that are common in Sloan Digital Sky Survey (SDSS) Data Release (DR)-16 quasar catalogue and Very Large ...
  • Frequency-dependent core shifts and parameter estimation for the blazar 3C 454.3 
    Mohan, Prashanth; Agarwal, A; Mangalam, A; Gupta, A. C; Wiita, P. J; Volvach, A. E; Aller, M. F; Aller, H. D; Gu, M. F; Lahteenmaki, A; Tornikoski, M; Volvach, L. N (Oxford University Press on behalf of the Royal Astronomical Society, 2015-09-11)
    We study the core shift effect in the parsec-scale jet of the blazar 3C 454.3 using the 4.8– 36.8 GHz radio light curves obtained from three decades of continuous monitoring. From a piecewise Gaussian fit to each flare, ...
  • Frequency-Dependent Damping in Propagating Slow Magneto-Acoustic Waves 
    Krishna Prasad, S; Banerjee, D; Doorsselaere, T. V (IOP Publishing, 2014-07-10)
    Propagating slow magneto-acoustic waves are often observed in polar plumes and active region fan loops. The observed periodicities of these waves range from a few minutes to a few tens of minutes and their amplitudes were ...
  • GROWTH on S190426c II: GROWTH-India Telescope search for an optical counterpart with a custom image reduction and candidate vetting pipeline 
    Kumar, Harsh; Bhalerao, Varun; Anupama, G. C; Barway, Sudhanshu; Coughlin, Michael W; De, Kishalay; Deshmukh, Kunal; Dutta, Anirban; Goldstein, Daniel A; Jassani, Adeem; Joharle, Simran; Karambelker, Viraj; Khandagale, Maitreya; Kumar, B; Saraogi, Divita; Sharma, Yashvi; Shenoy, Vedant; Singer, Leo; Singh, A; Waratkar, Gaurav (Oxford University Press on behalf of Royal Astronomical Society, 2022-11)
    S190426c/GW190426 152155 was the first probable neutron star–black hole merger candidate detected by the LIGO-Virgo Collaboration. We undertook a tiled search for optical counterparts of this event using the 0.7-m ...
  • GSC 2701-2527, A New Multiperiodic High-Amplitude Delta Scuti Variable 
    Kjurkchieva, D. P; Dimitrov, D. P; Ibryamov, S. I.; Srinivasa Rao, M (Astronomical Society of India, 2013-06)
    Our BVI photometric observations reveal that GSC 2701-2527 is a high amplitude ᵟ Scuti star with quite low temperature. The frequency analysis exhibits that it is multiperiodic pulsator. The obtained period ratio f1/ ...
  • H I 21cm observations and dynamical modelling of the thinnest galaxy: FGC 2366 
    Aditya, K; Banerjee, Arunima; Kamphuis, Peter; Mosenkov, Aleksandr; Makarov, Dmitry; Borisov, Sviatoslav (Oxford University Press on behalf of Royal Astronomical Society, 2023-11)
    Superthin galaxies are bulgeless low-surface brightness galaxies with unusually high major-to-minor axes ratio of the stellar disc, i.e. 10 < a/b < 20. We present Giant Metrewave Radio Telescope (GMRT) H I 21cm radio-synthesis ...
  • Homogeneous photospheric parameters and C abundances in G and K nearby stars with and without planets 
    da Silva, R; Milone, A. C; Reddy, B. E (EDP Sciences, 2011-02)
    Aims. We present a determination of photospheric parameters and carbon abundances for a sample of 172 G and K dwarf, subgiant, and giant stars with and without detected planets in the solar neighbourhood. The analysis was ...
  • The long-active afterglow of GRB 210204A: detection of the most delayed flares in a gamma-ray burst 
    Kumar, Harsh; Gupta, Rahul; Saraogi, Divita; Ahumada, Tomás; Andreoni, Igor; Anupama, G. C; Aryan, Amar; Barway, Sudhanshu; Bhalerao, Varun; Chandra, Poonam; Coughlin, Michael W; Dimple; Dutta, Anirban; Ghosh, Ankur; Ho, Anna Y. Q; Kool, E. C; Kumar, Amit; Medford, Michael S; Misra, Kuntal; Pandey, Shashi B; Perley, Daniel A; Riddle, Reed; Ror, Amit Kumar; Setiadi, Jason M; Yao, Yuhan (Oxford University Press on behalf of Royal Astronomical Society, 2022-06)
    We present results from extensive broadband follow-up of GRB 210204A over the period of 30 d. We detect optical flares in the afterglow at 7.6 × 105 s and 1.1 × 106 s after the burst: the most delayed flaring ever detected ...
  • A machine learning approach for classification of accretion states of black hole binaries 
    Sreehari, H; Nandi, Anuj (Oxford University Press on behalf of the Royal Astronomical Society, 2021-03)
    In this paper, we employ Machine Learning algorithms on multimission observations for the classification of accretion states of outbursting black hole X-ray binaries for the first time. Archival data from RXTE, Swift, MAXI, ...
  • 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 ...
  • Photometric identification of compact galaxies, stars, and quasars using multiple neural networks 
    Chaini, Siddharth; Bagul, Atharva; Deshpande, Anish; Gondkar, Rishi; Sharma, Kaushal; Vivek, M; Kembhavi, Ajit (Oxford University Press on behalf of Royal Astronomical Society, 2023-01)
    We present MargNet, a deep learning-based classifier for identifying stars, quasars, and compact galaxies using photometric parameters and images from the Sloan Digital Sky Survey Data Release 16 catalogue. MargNet consists ...
  • Postulating exoplanetary habitability via a novel anomaly detection method 
    Sarkar, Jyotirmoy; Bhatia, Kartik; Saha, Snehanshu; Safonova, M; Sarkar, Santonu (Oxford University Press on behalf of Royal Astronomical Society, 2022-03)
    A profound shift in the study of cosmology came with the discovery of thousands of exoplanets and the possibility of the existence of billions of them in our Galaxy. The biggest goal in these searches is whether there are ...

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