Related papers: Resolving the 10-40 keV Cosmic X-ray Background wi…
We present a new measurement of the space density of high redshift (3.0<z<4.5), X-ray selected QSOs obtained by exploiting the deep and uniform multiwavelength coverage of the COSMOS survey. We have assembled a statistically large (40…
Gamma-ray bursts (GRBs), which have isotropic energy up to $10^{54}$ erg, would be the ideal tool to study the properties of early universe: including dark energy, star formation rate, and the metal enrichment history of the Universe. We…
We present a cross-correlation analysis to constrain the faint galaxy contribution to the cosmic X-ray background (XRB). Cross-correlating faint optical galaxy catalogues with unidentified X-ray sources from 3 deep ROSAT fields we find that…
We investigate the serendipitous X-ray source population revealed in XMM-Newton observations targeted in the Galactic Plane within the region 315<l<45 and |b|<2.5 deg. Our study focuses on a sample of 2204 X-ray sources at intermediate to…
The origin of the X-ray background, in particular at hard (2-10 keV) energies, has been a debated issue for more than 30 years. The Chandra deep fields provide the deepest look at the X-ray sky and are the best dataset to study the X-ray…
The sensitivity of astronomical X-ray detectors is limited by the instrumental background. The background is especially important when observing low surface brightness sources that are critical for many of the science cases targeted by…
The information content of the autocorrelation function (ACF) of intensity fluctuations of the X-ray background (XRB) is analyzed. The tight upper limits set by ROSAT deep survey data on the ACF at arcmin scales imply strong constraints on…
We present an analysis of the spectral properties of the peculiar X-ray pulsar X Per based on INTEGRAL observations. We show that the source exhibits an unusually hard spectrum and is confidently detected by ISGRI up to more than 100 keV.…
The history of X-ray astronomy has shown that any advancement in our knowledge of the X-ray sky is strictly related to an increase in instrument sensitivity. At energies above 60 keV, there are interesting prospects for greatly improving…
Strong magnetic fields, synchrotron emission, and Compton scattering are omnipresent in compact celestial X-ray sources. Emissions in the X-ray energy band are consequently expected to be linearly polarized. X-ray polarimetry provides a…
We constrain X-ray spectral shapes for the ensemble of AGN based on the shape of the Cosmic X-ray Background (CXB). Specifically, we rule out regions of X-ray spectral parameter space that do not reproduce the CXB in the energy range 1-100…
Constellation-X (Con-X) will carry out two powerful and independent sets of tests of dark energy based on X-ray observations of galaxy clusters, providing comparable accuracy to other leading dark energy probes. The first group of tests…
The X-ray Background (XRB) probably originates from the integrated X-ray emission of active galactic nuclei (AGN). Modelling of its flat spectrum implies considerable absorption in most AGN. Compton down-scattering means that sources in…
Gamma ray bursts (GRBs) are the most energetic eruptions known in the Universe. Instruments such as Compton-GRO/BATSE and the GRB monitor on BeppoSAX have detected more than 2700 GRBs and, although observational confirmation is still…
We use Chandra deep observations of the Galactic Center (GC) region to improve the constraints on the unresolved fraction of the Galactic X-ray background (also known as the Galactic ridge X-ray emission). We emphasize the importance of…
A radiative decaying Big Bang relic with a mass $m_a\simeq 5-25 \,\rm eV$, which we dub "blue axion", can be probed with direct and indirect observations of the cosmic optical background (COB). The strongest bounds on blue-axion cold dark…
In a previous work we investigated the propagation of fast moving charged particles in a spatially constant but slowly time dependent pseudoscalar background, such as the one provided by cold relic axions. The background induces cosmic rays…
First results on a medium-deep X-ray survey in the "new" 5-10 keV band carried out with the MECS detectors onboard BeppoSAX are presented. The High Energy Llarge Area Survey (HELLAS) is aimed to directly explore a band where the energy…
Although about 40% of the soft X-ray background emission in 0.4 to 1 keV range has extragalactic origins and thus is totally blocked by the Galactic absorption in midplane directions, it decreases at most by about 20 % in midplane. Suzaku…
We use the radio-infrared (IR) flux correlation bet ween star-forming galaxies in the local universe to derive a simple analytical expression between the intensity of the IR background and the brightness t emperature of the radio…