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Browsing IIAP Publications by Title

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  • X-ray polarization observations of IC 4329A with IXPE: Constraining the geometry of the X-ray corona 
    Pal, Indrani; Stalin, C. S; Chatterjee, Rwitika; Agrawal, Vivek K (Indian Academy of Sciences, 2023-12)
    X-ray polarimetry is a powerful tool to probe the geometry of the hot X-ray corona in active galactic nuclei (AGN). Here, we present our results on the characterisation of the X-ray polarization of the radio-quiet Seyfert-type ...
  • X-ray spectra of Seyfert galaxies 
    Ghosh, K. K; Soundararajaperumal, S (Blackwell Publishing, 1992-11)
    A spectra analysis of eight Seyfert galaxies shows that while seven have soft excesses in their spectra, with no low-energy absorption, ESO 140-G43 exhibits low energy absorption, and may have weak soft excess that is ...
  • X-ray spectral and timing analysis of the Compton Thick Seyfert 2 galaxy NGC 1068 
    Pal, Indrani; Stalin, C. S; Parker, M. L; Agrawal, Vivek K; Marchesi, S (Oxford University Press on behalf of Royal Astronomical Society, 2022-12)
    We present the timing and spectral analysis of the Compton Thick Seyfert 2 active galactic nuclei NGC 1068 observed using NuSTAR and XMM–Newton. In this work for the first time we calculated the coronal temperature (⁠kTekTe⁠) ...
  • X-ray spectral properties of Seyfert galaxies and the unification scheme 
    Singh, V; Shastri, P; Risaliti, G (EDP Sciences, 2011-08)
    Context. The unification scheme of Seyfert galaxies predicts that the observed differences between types 1 and 2 Seyfert galaxies are solely due to the differing orientations of the toroidal-shaped obscuring material around ...
  • X-Ray Spectral Variability of the Seyfert Galaxy NGC4593 
    Ghosh, K. K; Soundararajaperumal, S (European Southern Observatory, 1993-06)
    X-ray (0.1-10 keV) spectra of NGC 4593 were obtained with EXOSAT on seven epochs between 1984 and 1986 using the low and medium energy detectors. Detailed results of the spectral analysis of the seven spectra (obtained ...
  • X-ray spectrum (0.1-10 keV) of the broad line radio galaxy - 3C 390.3 
    Ghosh, K. K; Sondararajaperumal, S (The American Astronomical Society, 1991-10)
    Results are presented of observations of the broad-line radio galaxy, 3C 390.3 that were made with Exosat on several occasions between 1984 and 1986 using low- (LE) and medium-energy (ME) detectors. Detailed findings of ...
  • X-ray spectrum of NGC 3783 - Detection of soft excess and an emission line 
    Ghosh, K. K; Soundararajaperumal, S; Kalai Selvi, M; Sivarani, T (EDP Sciences, 1992-02)
    Results of the X-ray (0.1-10 keV) spectral analysis of the Seyfert I galaxy, NGC 3783, which was observed with EXOSAT on three epochs between 1983 and 1985, are presented here. No low energy absorption, intrinsic to the ...
  • X-ray spectrum of the radio-loud quasar PKS 1217 + 023 
    Ghosh, K. K; Soundararajaperumal, S (EDP Sciences, 1991-12)
    A study of the X-ray (0.1-10 keV) spectrum from the radio-loud quasar, PKS 1217 + 023 is presented. This quasar was observed with Exosat on two epochs in January 29 and May 14, 1984. The data were obtained from the Exosat ...
  • The X-ray spectrum of the superluminal quasar 1928 + 73 
    Ghosh, K. K; Soundararajaperumal, S (Blackwell Publishing, 1992-02)
    Exosat observations (0.1-10 keV) of the radio-loud quasar 1928 + 73, which displays superluminal motion, were made at four epochs between 1983/283 and 1984/009, and spectra of this source are obtained from the Exosat ...
  • X-ray variability and the inner region in active galactic nuclei 
    Mohan, Prashanth; Mangalam, A (IOP Publishing, 2014-08-20)
    We present theoretical models of X-ray variability attributable to orbital signatures from an accretion disk including emission region size, quasi-periodic oscillations (QPOs), and its quality factor Q, and the emergence ...
  • X-Ray variability of active galactic nuclei in the soft and hard X-Ray bands 
    Chitnis, V. R; Pendharkar, J. K; Bose, D; Agrawal, V. K; Rao, A. R; Misra, R (Institute of Physics, 2009-06)
    We investigate the X-ray variability characteristics of hard X-ray-selected active galactic nuclei (AGNs)—based on Swift/Burst Alert Telescope—in the soft X-ray band using the Rossi X-ray Timing Explorer/All-Sky Monitor ...
  • X-shaped Radio Galaxies: Optical Properties, Large-scale Environment, and Relationship to Radio Structure 
    Joshi, Ravi; Gopal Krishna; Yang, Xiaolong; Shi, Jingjing; Yu, Si-Yue; Wiita; Paul J.; Ho, Luis C.; Wu, Xue-Bing; An, Tao; Wang, Ran; Subramanian, S; Yesuf, Hassen (IOP Publishing, 2019-12)
    In pursuit of clues to the origin of “ winged ” or X-shaped radio galaxies ( XRGs ) we investigate the parent galaxies of a large sample of 106 XRGs for optical – radio axes alignment, interstellar medium, black ...
  • The X-shaped Radio Galaxy J0725+5835 is Associated with an AGN Pair 
    Yang, Xiaolong; Ji, Jialu; Joshi, Ravi; Yang, Jun; An, Tao; Wang, Ran; Ho, Luis C; Roberts, David H; Saripalli, Lakshmi (IOP Publishing, 2022-07-01)
    X-shaped radio galaxies (XRGs) are those that exhibit two pairs of unaligned radio lobes (main radio lobes and wings). One of the promising models for the peculiar morphology is jet reorientation. To clarify this, we ...
  • The XMM-SERVS Survey: XMM-Newton point-source catalogs for the W-CDF-S and ELAIS-S1 fields 
    Ni, Qingling; Brand, W. N; Chen, Chien-Ting; Luo, Bin; Nyland, Kristina; Yang, Guang; Zou, Fan; Aird, James; Alexander, David M; Bauer, Franz Erik; Lacy, Mark; Lehmer, Bret D; Mallick, Labani; Salvato, Mara; Schneider, Donald P; Tozzi, Paolo; Traulsen, Iris; Vaccari, Mattia; Vignali, Cristian; Vito, Fabio; Xue, Yongquan; Banerji, Manda; Chow, Kate; Comastri, Andrea; Del Moro, Agnese; Gilli, Roberto; Mullaney, James; Paolillo, Maurizio; Schwope, Axel; Shemmer, Ohad; Sun, Mouyuan; Timlin III, John D; Trump, Jonathan R (IOP Publishing, 2021-09)
    We present the X-ray point-source catalogs in two of the XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS) fields, W-CDF-S (4.6 deg2) and ELAIS-S1 (3.2 deg2), aiming to fill the gap between deep pencil-beam ...
  • XX Cam -The Inactive R CrB Star 
    Kameswara Rao, N; Ashok, N. M; Kulkarni, P. V (Indian Academy of Sciences, 1980-09)
    Infrared observations obtained six years apart of the R CrB type star XX Cam do not show any infrared excess, unlike all other members of the class. The observed colours match a 7000 K black body energy distribution quite ...
  • Yields of nucleosynthesis from massive and intermediate mass stars and constraints on their final evolution 
    Mallik, D. C. V; Mallik, S. G. V (Indian Academy of Sciences, 1985-09)
    Nucleosynthetic yields and production rates of He and heavy elements are derived using recent revisions in O star counts and the stellar models of Maeder (1981). The current production rates and yields are significantly ...
  • Young LMC star clusters as a test for stellar evolutionary models. 
    Subramaniam, A; Sagar, R (The European Southern Observatory, 1995-05)
    We compare the observed colour-magnitude diagrams (CMD) and the main sequence luminosity functions (LFs) of four Large Magellanic Cloud (LMC) star clusters namely, NGC 1711, NGC 2004, NGC 2164 and NGC 2214 with the synthetic ...
  • The Young Open Star Clusters: Stability and Structure 
    Pandey, A. K; Mahra, H. S; Sagar, R (American Astronomical Society, 1990-02)
    It is found to the differential extinction ΔE (B-V) in open clusters which may be due to the presence of gas and dust, decreases systematically with age of the cluster. Consequently we can infer that the average gas removal ...
  • Young star clusters of our galaxy and the large magellanic cloud as test for stellar evolutionary models 
    Sagar, R; Subramaniam, A (Universidad Nacional Autonoma de Mexico, 1999)
    A comparison of the colour-magnitude diagrams (CMDs) and the main sequence luminosity function (LF) of five young Galactic star clusters and four young Large Magellanic Cloud star clusters derived from precise CCD observations ...
  • Young Stars and Nonstellar Emission in the Aligned Radio Galaxy 3C 256 
    Simpson, C; Eisenhardt, P; Armus, L; Chokshi, A; Dickinson, M; Djorgovski, S. G; Elston, R; Jannuzi, B. T; McCarthy, P. J; Pahre, M. A; Soifer, B. T (The American Astronomical Society, 1999-11)
    We present ground-based images of the z=1.824 radio galaxy 3C 256 in the standard BVRIJHK filters and an interference filter centered at 8800 Å, a Hubble Space Telescope image in a filter dominated by Lyα emission (F336W), ...

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