相关论文: pi Aqr is another gamma-Cas object

Anomalous X-ray Pulsars (AXPs) are a class of rare X-ray pulsars whose energy source has been perplexing for some 20 years. Unlike other, better understood X-ray pulsars, AXPs cannot be powered by rotation or by accretion from a binary…

Prominent Fe K line emission is detected at around 6.7 keV in the XMM-Newton spectrum of the ultraluminous infrared galaxy Arp220. The continuum emission in the 2.5-10 keV band is flat and a few other spectral features are suggested. The…

Active Galactic Nuclei (AGN) are now known to be strong gamma-ray emitters. After briefly describing AGN classification and the main ideas behind unified schemes, I summarize the main properties of blazars (that is BL Lacs and flat-spectrum…

The first part of this article is a historical and physical introduction to quasars and their close cousins, called Active Galactic Nuclei (AGN). In the second part, I argue that our progress in understanding them has been unsatisfactory…

Gamma-ray binaries are binary systems where the energy flux peaks in the gamma-ray energy band. They harbour a compact object (a neutron star or a black hole) orbiting around a massive star that provides a strong radiation field. It is…

An enigmatic, small class of IR and X-ray luminous sources, named ``Composite'' starburst/Seyfert galaxies, has been defined from IRAS and RASS data. The objects have optical spectra dominated by the features of HII galaxies (plus, in some…

The binary system $\eta$ Carinae is a unique laboratory in which to study particle acceleration to high energies under a wide range of conditions, including extremely high densities around periastron. To date, no consensus has emerged as to…

Despite that gamma-ray bursts is a phenomenon quite different from accreting compact objects, it could be that their hard X-ray emission is associated with a very similar mechanism of energy dissipation. In both cases, we could deal with…

Interferometric observations of two well-known Be stars, gamma Cas and phi Per, were collected and analyzed to determine the spatial characteristics of their circumstellar regions. The observations were obtained using the Navy Prototype…

HESS J1832-093 is a member of the rare class of gamma-ray binaries, as recently confirmed by the detection of orbitally modulated X-ray and gamma-ray emission with a period of ~86 d. The spectral type of the massive companion star has been…

Optically quiescent quasars (OQQs) represent a recently systematised class of infrared-luminous active galactic nuclei (AGN) which have galaxy-like optical continua. They may represent an interesting, brief phase in the AGN life cycle, e.g.…

Microquasars, X-ray binary systems that generate relativistic jets, were discovered in our Galaxy in the last decade of the XXth century. Their name indicates that they are manifestations of the same physics as quasars but on a completely…

We present a comparative study of the circumstellar disks in Be/X-ray binaries and isolated Be stars based upon the H-alpha emission line. From this comparison it follows that the overall structure of the disks in the Be/X-ray binaries is…

Presently there are several classes of detected gamma-ray extragalatic sources. They are mostly associated to active galactic nuclei (AGN) and (at soft gamma rays) to gamma-ray bursts (GRB), but not only. Active galactic nuclei consist of…

The X-ray binary LSI +61 303, consisting of a main sequence Be star and a compact object has been detected in the TeV range with MAGIC and VERITAS, and showed a clear intensity modulation as a function of the orbital phase. We describe a…

Quark-novae leave behind quark stars with a surrounding metal-rich fall-back (ring-like) material. These compact remnants have high magnetic fields and are misconstrued as magnetars; however, several observational features allow us to…

Microquasars are accreting X-ray binary systems with non-thermal radio jets. In some of these systems the jet is expected to be strongly misaligned with the perpendicular to the orbital plane. If the donor star is an early-type star, the…

High Mass X-ray Binaries (HMXBs) are interesting objects that provide a wide range of observational probes to the nature of the two stellar components, accretion process, stellar wind and orbital parameters of the systems. A large fraction…

We study the mid-egress eclipse timing data gathered for the cataclysmic binary HU Aquarii during the years 1993-2014. The (O-C) residuals were previously attributed to a single ~7 Jupiter mass companion in ~5 au orbit or to a stable…

Be/X-ray binary systems provide an excellent opportunity to study the physics around neutron stars through the study of the behaviour of matter around them. Intermediate and low-luminosity type outbursts are interesting because they provide…