Search Publications
A novel "spectral‑ratio model fitting" to resolve complicated X‑ray spectral variations in active galactic nuclei
Ebisawa, Ken; Mizumoto, Misaki; Midooka, Takuya
Radiation‑magnetohydrodynamic simulation of the active galactic nuclei predicts the presence of the strong accretion disk wind, which gets unstable far from the central region and turns into gas clumps. These inner wind and outer clumps may be actually observed as the ultrafast outflows (UFOs) and the clumpy absorbers, respectively. We call this p…
Quasi‑periodic oscillations are more than timing features: Applying the accretion‑ejection instability in super massive black‑holes
Varniere, Peggy
Low frequency quasi‑periodic oscillations (LFQPOs) have always been seen uniquely as a timing feature, with most models focused on reproducing only their timing behavior. Previously, the accretion‑ejection instability (AEI) predicted the existence of a more subtle effect on their energy spectrum. In the case of low mass X‑ray binaries (LMXB), that…
Measurements of visual double stars with PISCO2 at the Nice 76‑cm refractor in 2013–2014 (new data) and in 2015
Vakili, F.; Rivet, J. -P.; Ling, J. F. +11 more
We present relative astrometric and photometric measurements of visual double stars made in 2013–2015, with PISCO2 installed at the 76‑cm refractor of Côte d'Azur Observatory in Nice (France). Our observing list contains orbital couples as well as double stars whose motion is still uncertain. Most of the observations were done in 2015, but some ot…
Decomposition of the central structure of NGC 2273 in the NIR: A case study
Quirrenbach, A.; Gredel, R.; Thompson, D. +11 more
The Seyfert 2 galaxy NGC 2273 is a prime target to explore how active nuclei can be fed. It has a star‑forming innermost nuclear ring with a radius of 0.33kpc from where material may be funneled to the supermassive black hole in its center. In this article, we discuss high‑resolution adaptive optics aided JHKs images of NGC 2273 taken with the Lar…
Confirmation and characterization of neglected WDS systems using Gaia data release 3 and the virtual observatory
Cortés-Contreras, M.; Solano, E.; Rodrigo, C. +2 more
The aim of this article is making use of the Gaia DR3 catalogue and virtual observatory tools, to confirm and characterize 428 binary and multiple stellar systems classified as neglected (only one observation) in the Washington Double Star Catalogue (WDS). The components of the stellar systems have the same parallax and proper motion (within the e…
Soft excess in AGN with relativistic X‑ray reflection
Mathew, Blesson; Dewangan, Gulab C.; Ezhikode, Savithri H. +1 more
The soft X‑ray excess, emission below 2 keV over the X‑ray power‑law, is a marked spectral component in the X‑ray spectra of many Seyfert 1 galaxies. We investigate if the observed soft X‑ray excess in a sample of Seyfert 1s is in accordance with the prediction of the relativistic reflection model by analyzing the XMM‑Newton and NuSTAR spectra. Th…
Possible optical counterparts of ULXs in NGC 1672
Sonbas, Eda; Allak, Sinan; Akyuz, Aysun +1 more
In this study, we use archival data from Hubble Space Telescope (HST), Chandra, XMM‑Newton, and Swift‑XRT, to probe the nature of 9 (X1‑X9) candidate ultraluminous X‑ray sources (ULXs) in NGC 1672. Our study focuses on using the precise source positions obtained via improved astrometry based on Chandra and HST observations to search for and identi…
Searching for overlooked TDEs in the 4XMM catalogue
Risaliti, Guido; Sacchi, Andrea; Miniutti, Giovanni
Tidal disruption events (TDEs) are usually discovered as bright transients, either in the X‑ray or optical/UV band. These events are often characterized by a "super‑soft" emission in the X‑ray band, which has not been observed in any other extragalactic source, with few exceptions (novae and supersoft active galactic nuclei, AGN), which can howeve…
X‑HESS: A large sample of highly accreting serendipitous AGN under the XMM‑Newton microscope
Guainazzi, M.; Piconcelli, E.; Tombesi, F. +3 more
The bulk of X‑ray spectroscopic studies of active galactic nuclei (AGN) are focused on local () sources with low‑to‑moderate (<0.3) Eddington ratio (). It is then mandatory to overcome this limitation and improve our understanding of highly accreting AGN. In this work, we present the preliminary results from the analysis of a sample of high‑ ra…