Search Publications
Peculiar temporal and spectral features in highly obscured HMXB pulsar IGR J16320-4751 using XMM-Newton
Paul, Biswajit; Varun; Iyer, Nirmal
IGR J16320-4751 is a highly obscured HMXB source containing a very slow neutron star (Pspin ∼ 1300 sec) orbiting its supergiant companion star with a period of ∼9 days. It shows high column density (NH ∼ 2 - 5 × 1023cm-2) in the spectrum, and a large variation in flux along the orbit despite not being an…
Study of Central Intensity Ratio of Seyfert Galaxies in Nearby Universe
Ravikumar, C. D.; Aswathy, S.; Vinod, K. T. +1 more
We use the recently discovered simple photometric parameter Central Intensity Ratio (CIR) determined for a sample of 57 nearby (z < 0.02) Seyfert galaxies to explore the central features of galaxies and their possible connection with galaxy evolution. The sample of galaxies shows strong anti-correlation between CIR and mass of their central sup…
TCP J18224935-2408280: a symbiotic star identified during outburst
Sonith, L. S.; Kamath, U. S.
TCP J18224935-2408280 was reported to be in outburst on 2021 May 19. Follow-up spectroscopic observations confirmed that the system was a symbiotic star. We present optical spectra obtained from the Himalayan Chandra Telescope during 2021-22. The early spectra were dominated by Balmer lines, He I lines and high ionization lines such as He II. In t…
Imaging Preflare Broadband Pulsations in the Decimetric-metric Wavelengths
Chen, Yao; Tan, Baolin; Zheng, Ruisheng +4 more
Preflare activities contain critical information about the precursors and causes of solar eruptions. Here we investigate the characteristics and origin of a group of broadband pulsations (BBPs) in the decimetric-metric wavelengths that took place during the preflare stage of the M7.1 flare on 2011 September 24. The event was recorded by multiple s…
Constraining X-Ray Variability of the Blazar 3C 273 Using XMM-Newton Observations over Two Decades
Mohorian, Maksym; Bhatta, Gopal; Adhikari, Tek P. +5 more
Blazars exhibit relentless variability across diverse spatial and temporal frequencies. The study of long- and short-term variability properties observed in the X-ray band provides insights into the inner workings of the central engine. In this work, we present timing and spectral analyses of the blazar 3C 273 using the X-ray observations from the…
Optical and X-Ray Studies of Marginal Contact Binary RW Dor Using TESS and XMM-Newton Observatories
Sriram, K.; Mamatha Rani, G.
Marginal short-period contact binaries are important to understand as they pose a different physical scenario than the predicted theoretical model based on the thermal relaxation oscillation mechanism due to their shallow degree of contact. Here we present the optical and X-ray studies of a contact binary source RW Dor using the Transiting Exoplan…
Influence of the dynamic classification of asteroids on observation astrometric errors: a statistical analysis
Stronati, N.; Faggioli, L.; Micheli, M. +1 more
The ephemerides of minor planets are computed on the basis of astrometric observations. The asteroid orbit determination process requires these observations to be properly weighted to take into account the expected accuracy of the data. If not directly provided by the observers, the weights are, in general, computed after a station-specific statis…
A Comprehensive Study of Soft X-ray Absorption Features in GX 13+1 Using XMM-Newton Observations
Mahato, Rabindra; Baruah, Monmoyuri
In this study, a comprehensive analysis of the reflection grating spectrometer (RGS) data (energy range 0.33 keV to 2.5 keV) of GX 13+1 from the XMM-Newton space observatory was conducted. Numerous absorption lines have been described in earlier publications, although the majority of these investigations focused on the energy range between 3 keV a…
Temporal and Latitudinal Variation in Penumbra-Umbra Ratios of the Sunspots: Analyses of RGO, Kodaikanal and Debrecen Databases
Takalo, Jouni
We study the latitudinal distribution and temporal evolution of the sunspot penumbra-umbra ratio (q ) for the even and odd Solar Cycles 12 - 24 of RGO sunspot groups, SC21 - SC24 of Debrecen sunspot groups and Kodaikanal sunspot dataset for SC16 - SC24. We find that RGO even (odd) Cycles have q -values 5.20 (4.75), Kodaikanal even (odd) cycles hav…
[C I] and [C II] emission in the circumstellar envelope of IRC +10216. I. Observational data and NLTE modelling of the [C I] emission
Menten, K. M.; Wyrowski, F.; Wiesemeyer, H. +1 more
Context. The envelopes of evolved late-type stars on the asymptotic giant branch are characterised by a complex chemistry that is close to thermochemical equilibrium near the stellar surface; however, in the outer envelope, it is dominated by radical reactions, assisted by a photo-chemistry driven by the interstellar radiation field.
Aims: Th…