Light bending and X-ray echoes from behind a supermassive black hole.

The innermost regions of accretion disks around black holes are strongly irradiated by X-rays that are emitted from a highly variable, compact corona, in the immediate vicinity of the black hole. The X-rays that are seen reflected from the disk, and the time delays, as variations in the X-ray emission echo or 'reverberate' off the disk, provide a view of the environment just outside the event horizon. I Zwicky 1 (I Zw 1) is a nearby narrow-line Seyfert 1 galaxy.

The exceptional X-ray evolution of SN 1996cr in high resolution.

We present X-ray spectra spanning 18 yr of evolution for SN 1996cr, one of the five nearest SNe detected in the modern era. HETG exposures in 2000, 2004, and 2009 allow us to resolve spectrally the velocity profiles of Ne, Mg, Si, S, and Fe emission lines and monitor their evolution as tracers of the ejecta-circumstellar medium interaction. To explain the diversity of X-ray line profiles, we explore several possible geometrical models.

A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger.

Mergers of neutron stars are known to be associated with short γ-ray bursts. If the neutron-star equation of state is sufficiently stiff (that is, the pressure increases sharply as the density increases), at least some such mergers will leave behind a supramassive or even a stable neutron star that spins rapidly with a strong magnetic field (that is, a magnetar). Such a magnetar signature may have been observed in the form of the X-ray plateau that follows up to half of observed short γ-ray bursts.

Supermassive black-hole growth over cosmic time: active galaxy demography, physics, and ecology from Chandra surveys.

Extragalactic X-ray surveys over the past decade have dramatically improved understanding of the majority populations of active galactic nuclei (AGNs) over most of the history of the universe. Here we briefly highlight some of the exciting discoveries about AGN demography, physics, and ecology, with a focus on results from Chandra. We also discuss some key unresolved questions and future prospects.

Broad line emission from iron K- and L-shell transitions in the active galaxy 1H 0707-495.

Since the 1995 discovery of the broad iron K-line emission from the Seyfert galaxy MCG-6-30-15 (ref. 1), broad iron K lines have been found in emission from several other Seyfert galaxies, from accreting stellar-mass black holes and even from accreting neutron stars. The iron K line is prominent in the reflection spectrum created by the hard-X-ray continuum irradiating dense accreting matter.

Rapid growth of black holes in massive star-forming galaxies.

The tight relationship between the masses of black holes and galaxy spheroids in nearby galaxies implies a causal connection between the growth of these two components. Optically luminous quasars host the most prodigious accreting black holes in the Universe, and can account for greater than or approximately equal to 30 per cent of the total cosmological black-hole growth. As typical quasars are not, however, undergoing intense star formation and already host massive black holes (> 10(8)M(o), where M(o) is the solar mass), there must have been an earlier pre-quasar phase when these black holes grew (mass range approximately (10(6)-10(8))M(o)).

The Chandra Deep Field-North Survey and the cosmic X-ray background.

Chandra has performed a 1.4 Ms survey centred on the Hubble Deep Field-North (HDF-N), probing the X-ray Universe 55-550 times deeper than was possible with pre-Chandra missions. We describe the detected point and extended X-ray sources and discuss their overall multi-wavelength (optical, infrared, submillimetre and radio) properties.

Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre.

The nuclei of most galaxies are now believed to harbour supermassive black holes. The motions of stars in the central few light years of our Milky Way Galaxy indicate the presence of a dark object with a mass of about 2.6 x 106 solar masses (refs 2, 3).

Hot plasma and black hole binaries in starburst galaxy M82.

High-resolution x-ray observations of the prototype starburst galaxy Messier 82 (M82) obtained with the advanced CCD (charge-coupled device) imaging spectrometer on board the Chandra X-ray Observatory provide a detailed view of hot plasma and energetic processes. Plasma with temperature of about 40,000,000 kelvin fills the inner 1 kiloparsec, which is much hotter than the 1,000,000 to 2,000,000 kelvin interstellar medium component in the Milky Way Galaxy. Produced by many supernova explosions, this central region is overpressurized and drives M82's prominent galactic wind into the intergalactic medium.

Discovery of Narrow X-Ray Absorption Lines from NGC 3783 with the Chandra High Energy Transmission Grating Spectrometer.

We present the first grating-resolution X-ray spectra of the Seyfert 1 galaxy NGC 3783, obtained with the High Energy Transmission Grating Spectrometer on the Chandra X-Ray Observatory. These spectra reveal many narrow absorption lines from the H-like and He-like ions of O, Ne, Mg, Si, S, and Ar as well as Fe xvii-Fe xxi L-shell lines. We have also identified several weak emission lines, mainly from O and Ne.

X-Rays from the Highly Polarized Broad Absorption Line QSO CSO 755.

We present results from a BeppoSAX observation of the broad absorption line (BAL) QSO CSO 755, which was observed as part of our program to investigate the X-ray properties of highly polarized BAL QSOs. CSO 755 is clearly detected by the BeppoSAX Medium-Energy Concentrator Spectrometers, making it the highest redshift (z=2.88) and most optically luminous (MV=-27.

ROSAT Observations of X-ray Emissions from Jupiter During the Impact of Comet Shoemaker-Levy 9.

Röntgensatellit (ROSAT) observations made shortly before and during the collision of comet Shoemaker-Levy 9 with Jupiter show enhanced x-ray emissions from the planet's northern high latitudes. These emissions, which occur at System III longitudes where intensity enhancements have previously been observed in Jupiter's ultraviolet aurora, appear to be associated with the comet fragment impacts in Jupiter's southern hemisphere and may represent brightenings of the jovian x-ray aurora caused either by the fragment impacts themselves or by the passage of the fragments and associated dust clouds through Jupiter's inner magnetosphere.