Search Publications
Contrasting X-ray/UV time-lags in Seyfert 1 galaxies NGC 4593 and NGC 7469 using AstroSat observations
Papadakis, I. E.; Singh, K. P.; Dewangan, G. C. +6 more
We study accretion disc-corona connection in Seyfert 1 galaxies using simultaneous UV/X-ray observations of NGC 4593 (2016 July 14-18) and NGC 7469 (2017 October 15-19) performed with AstroSat. We use the X-ray (0.5-7.0 keV) data acquired with the Soft X-ray Telescope (SXT) and the UV (FUV: 130-180 nm, NUV: 200-300 nm) data obtained with the Ultra…
Sub-mm/mm optical properties of real protoplanetary matter derived from Rosetta/MIRO observations of comet 67P
Blum, Jürgen; Gundlach, Bastian; Wolf, Sebastian +6 more
Optical properties are required for the correct understanding and modelling of protoplanetary and debris discs. By assuming that comets are the most pristine bodies in the Solar system, our goal is to derive optical constants of real protoplanetary material. We determine the complex index of refraction of the near-surface material of comet 67P/Chu…
An investigation of the '10 keV feature' in the spectra of accretion powered X-ray pulsars with NuSTAR
Paul, Biswajit; Rana, Vikram; Manikantan, Hemanth
Some of the accreting X-ray pulsars are reported to exhibit a peculiar spectral feature at ~10 keV, known as the '10 keV feature'. The feature has been characterized as either an emission line or an absorption line, and its origin is unknown. It has been found in multiple observations of the same source by different observatories, but not all the …
On the gamma-ray emission from the core of the Sagittarius dwarf galaxy
Linden, Tim; Pace, Andrew B.; Strigari, Louis E. +5 more
We use Fermi-LAT data to analyse the faint gamma-ray source located at the centre of the Sagittarius (Sgr) dwarf spheroidal galaxy. In the 4FGL-DR3 catalogue, this source is associated with the globular cluster, M54. We investigate the spectral energy distribution and spatial extension of this source, with the goal of testing two hypotheses: (1) t…
BASS-XL: X-ray variability properties of unobscured active galactic nuclei
Kawamuro, Taiki; Ricci, Claudio; Bauer, Franz E. +15 more
We investigate the X-ray variability properties of Seyfert 1 Galaxies belonging to the BAT AGN Spectroscopic Survey (BASS). The sample includes 151 unobscured (NH < 1022 cm-2) AGNs observed with XMM-Newton for a total exposure time of ~27 ms, representing the deepest variability study done so far with high signa…
Enlightening the dynamical evolution of Galactic open clusters: an approach using Gaia DR3 and analytical descriptions
Corradi, W. J. B.; Maia, F. F. S.; Angelo, M. S. +1 more
Most stars in our Galaxy form in stellar aggregates, which can become long-lived structures called open clusters (OCs). Along their dynamical evolution, their gradual depletion leave some imprints on their structure. In this work, we employed astrometric, photometric, and spectroscopic data from the Gaia DR3 catalogue to uniformly characterize a s…
A remarkably stable accretion disc in the Seyfert galaxy MCG-5-23-16
Ingram, Adam; Bianchi, Stefano; Matt, Giorgio +12 more
MCG-5-23-16 is a Seyfert 1.9 galaxy at redshift z = 0.008 49. We analyse here the X-ray spectra obtained with X-ray Multi-Mirror (XMM)-Newton and Nuclear Spectroscopic Telescope Array (NuSTAR) data, which are the first contemporaneous observations with these two X-ray telescopes. Two reflection features, producing a narrow core and a broad compone…
Coronal properties of low-accreting AGNs using Swift, XMM-Newton, and NuSTAR observations
Safi-Harb, Samar; Chang, Hsiang-Kuang; Ricci, Claudio +6 more
We studied the broad-band X-ray spectra of Swift/Burst Alert Telescope selected low-accreting active galactic nuclei (AGNs) using the observations from XMM-Newton, Swift, and NuSTAR in the energy range of 0.5-150 keV. Our sample consists of 30 AGNs with Eddington ratio, λEdd < 10-3. We extracted several coronal parameters …
Discovery of double BSS sequences in the old Galactic open cluster Berkeley 17
Vaidya, Kaushar; Rao, Khushboo K.; Agarwal, Manan +1 more
Blue straggler stars (BSS) are peculiar objects which normally appear as a single broad sequence along the extension of the main sequence. Only four globular clusters (GCs) have been observed to have two distinct and parallel BSS sequences. For the first time for any open cluster (OC), we report double BSS sequences in Berkeley 17. Using the machi…
Stirred but not shaken: a multiwavelength view of HD 16743's debris disc
del Burgo, C.; Milli, J.; Kral, Q. +6 more
Planetesimals - asteroids and comets - are the building blocks of planets in protoplanetary discs and the source of dust, ice, and gas in debris discs. Along with planets they comprise the left-over material after star formation that constitutes a planetary system. Planets influence the dynamics of planetesimals, sculpting the orbits of debris bel…