Search Publications
Measurement of coronal properties of Seyfert galaxies from NuSTAR's hard X-ray spectrum
Stalin, C. S.; Rani, Priyanka
Precise measurement of the coronal properties of Active Galactic Nuclei (AGN) requires the availability of high signal-to-noise ratio data covering a wide range of X-ray energies. The Nuclear Spectroscopic Telescope Array (NuSTAR) which is highly sensitive to earlier missions in its operational energy range of 3–79 keV, allows us to arrive at prec…
Suzaku observation of the eclipsing high mass X-ray binary pulsar XTE J1855-026
Paul, Biswajit; Devasia, Jincy
We report results from analysis performed on an eclipsing supergiant high mass X-ray binary pulsar XTE J1855-026 observed with the X-ray Imaging Spectrometer (XIS) on-board Suzaku Observatory in April 2015. Suzaku observed this source for a total effective exposure of
Dust color temperature distribution of two FIR cavities at IRIS and AKARI maps
Jha, A. K.; Aryal, B.
By systematically searching the region of far infrared loops, we found a number of huge cavity-like dust structures at
Short timescale UV variability study in NGC 4151 using IUE data
Doddamani, Vijayakumar H.; Vedavathi, P.
IUE has made very successful long term and intense short time-scale monitoring spectroscopic study of NGC 4151, a Seyfert 1 galaxy for over nearly 18 years from its launch in 1978 to 1996. The long-term observations have been useful in understanding the complex relation between UV continuum and emission line variability Seyfert galaxies. In this p…
In-orbit Performance of UVIT and First Results
Stalin, C. S.; Rao, N. Kameswara; Sutaria, F. +23 more
The performance of the ultraviolet telescope (UVIT) on-board AstroSat is reported. The performance in orbit is also compared with estimates made from the calibrations done on the ground. The sensitivity is found to be within
The Radio and X-ray Mode-Switching Pulsar PSR B0943+10
Mereghetti, Sandro; Rigoselli, Michela
Observations obtained in the last years challenged the widespread notion that rotation-powered neutron stars are steady X-ray emitters. Besides a few allegedly rotation-powered neutron stars that showed 'magnetar-like' variability, a particularly interesting case is that of PSR B0943+10. Recent observations have shown that this pulsar, well studie…
Evidence of Magnetoacoustic Oscillations above the Brightened and Magnetically Active Quiet-Sun
Srivastava, A. K.; Dwivedi, B. N.
We study the near photospheric Fe I 6302 Å (V-component) and chromospheric Ca II H 3968 Å radiance oscillations in the lower solar atmosphere above the four brightened and magnetically active regions of the quiet-Sun as observed by the solar optical telescope onboard Hinode. At the chosen locations (L1, L3, L4), we obtain the statistically signifi…
A Road Map for the Generation of a Near-Infrared Guide Star Catalog for Thirty Meter Telescope Observations
Subramaniam, Annapurni; Simard, Luc; Subramanian, Smitha +5 more
The near-infrared instruments in the upcoming Thirty Meter Telescope (TMT) will be assisted by a multi conjugate Adaptive Optics (AO) system. For the efficient operation of the AO system, during observations, a near-infrared guide star catalog which goes as faint as 22 mag in JVega band is essential and such a catalog does not exist. A …
Measures of the Soft X-ray Excess as an Eigenvector 1 Parameter for Active Galactic Nuclei
Marziani, P.; Perea, J.; del Olmo, A. +2 more
We present a preliminary analysis of X-ray data of quasars in the context of the 4D eigenvector 1 parameter space (Sulentic et al. 2000a, b). 4DE1 serves as a surrogate H-R diagram for representing empirical diversity among quasars and identifying the physical drivers of the diversity. The soft X-ray spectral index (Γsoft) was adopted a…
Spicules Intensity Oscillations in SOT/HINODE Observations
Ahangarzadeh Maralani, A. R.; Tavabi, E.; Ajabshirizadeh, A. +1 more
We study the coherency of solar spicules intensity oscillations with increasing height above the solar limb in quiet Sun, active Sun and active region using observations from HINODE/SOT. Existence of coherency up to transition region strengthens the theory of the coronal heating and solar wind, through energy transport and photospheric oscillation…