9 papers
The X-ray-to-UV relation does not evolve in homogeneous quasar samples
G. Risaliti, E. Lusso, E. Nardini +6
We present a new, highly homogeneous quasar sample with X-ray and UV observations optimized to reliably estimate distances via the non-linear X-ray-to-UV relation. Cross-matching t…
A new Chandra look at the globular cluster NGC 6540 and its peculiar X-ray flaring source
A. Sacchi, S. Mereghetti, R. Di Stefano +4
We report the results of a deep ( ks) Chandra exposure of the globular cluster NGC 6540, obtained by combining three observations carried out in 2023-2024 to investigate…
A supermassive black hole under the radar: Repeating X-ray variability in a Seyfert galaxy
Matteo Imbrogno, Andrea Sacchi, Giovanni Miniutti +4
In the last few years, a few supermassive black holes (SMBHs) have shown short-term (of the order of hours) X-ray variability. Given the limited size of the sample, every new addit…
Chandra Rules Out Super-Eddington Accretion Models For Little Red Dots
Andrea Sacchi, Akos Bogdan
One of the most puzzling discoveries by JWST is the population of high-redshift, red, and compact galaxies dubbed little red dots (LRDs). Based on broad-line diagnostics, these gal…
Detection of Anisotropies in the Circumgalactic Medium of Disk Galaxies: Supermassive Black Hole Activity or Star Formation-driven Outflows?
Andrea Sacchi, Akos Bogdan, Nhut Truong
Gamma and X-ray observatories have revealed spectacular structures in the emission of the tenuous hot gas surrounding the Milky Way (MW), known as the Fermi and eROSITA bubbles. Ga…
Hyperluminous Supersoft X-Ray Sources in the Chandra Catalog
Andrea Sacchi, Kevin Paggeot, Steven Dillmann +2
Hyperluminous supersoft X-ray sources, such as bright extragalactic sources characterized by particularly soft X-ray spectra, offer a unique opportunity to study accretion onto sup…