The X-ray spectrum of the Seyfert I galaxy Markarian 766: Dusty warm absorber or relativistic emission lines?

Competing models for broad spectral features in the soft X-ray spectrum of the Seyfert I galaxy Mrk 766 are tested against data from a 130 ks XMM-Newton observation. A model including relativistically broadened Lyalpha emission lines of O VIII N VII and C VI is a better fit to 0.3-2 keV XMM RGS data than a dusty warm absorber. Moreover, the measured depth of neutral iron absorption lines in the spectrum is inconsistent with the magnitude of the iron edge required to produce the continuum break at 17-18 Angstrom in the dusty warm absorber model. The relativistic emission line model can reproduce the broadband (0.1-12 keV) XMM EPIC data with the addition of a fourth line to represent emission from ionized iron at 6.7 keV and an excess due to reflection at energies above the iron line. The pro le of the 6.7 keV iron line is consistent with that measured for the low-energy lines. There is evidence in the RGS data, at the 3sigma level, of spectral features that vary with source flux. The covering fraction of warm absorber gas is estimated to be 12%. Iron in the warm absorber is found to be overabundant with respect to CNO, compared to solar values

Multiwavelength observations of radio galaxy 3C 120 with XMM-newton

We present XMM-Newton observations of the radio galaxy 3C 120. Contemporaneous radio, millimeter-wave, and optical data provide additional constraints on the spectral energy distribution and physical state of the active galactic nucleus. The hard X-ray spectrum contains a marginally resolved Fe I Kα emission line with FWHM = 9000 × 3000 km s and an equivalent width of 57 ± 7 eV. The line arises via fluorescence in a broad-line region with covering fraction of 0.4. There is no evidence of relativistically broad Fe Kα, contrary to some previous reports. An excess of 0.3-2 keV soft X-ray continuum over an extrapolation of the hard X-ray power law may arise in a disk corona. A break in the X-ray spectrum below 0.6 keV indicates an excess neutral hydrogen column density of NE = (1.0-1.6) × 10 cm . However, the neutral absorber must have an oxygen abundance of <1/40 of the solar value to explain the absence of an intrinsic or intervening O I edge. There is no ionized absorption in the soft X-ray spectrum, and we do not detect previously claimed 0 VIII absorption from the intervening intergalactic medium. Radio observations at 37 GHz show a fast, high-frequency flare beginning near the time of the XMM-Newton observation, which has no obvious effect on the X-ray spectrum. The X-ray spectrum, including the soft excess, became harder as the X-ray flux decreased, with an estimated pivot energy of 40 keV. The UVand soft X-ray fluxes are strongly correlated over the 120 ks duration of the XMM-Newton observation. This is qualitatively consistent with Comptonization of UV photons by a hot corona. -1 21 -

The Swift gamma-ray burst mission

The Swift mission, scheduled for launch in 2004, is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is a first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the way for future rapid-reaction and multiwavelength missions. It will be far more powerful than any previous GRB mission, observing more than 100 bursts yr(-1) and performing detailed X-ray and UV/optical afterglow observations spanning timescales from 1 minute to several days after the burst. The objectives are to (1) determine the origin of GRBs, (2) classify GRBs and search for new types, (3) study the interaction of the ultrarelativistic outflows of GRBs with their surrounding medium, and (4) use GRBs to study the early universe out to z>10. The mission is being developed by a NASA-led international collaboration. It will carry three instruments: a new-generation wide-field gamma-ray (15-150 keV) detector that will detect bursts, calculate 1'-4' positions, and trigger autonomous spacecraft slews; a narrow-field X-ray telescope that will give 5" positions and perform spectroscopy in the 0.2-10 keV band; and a narrow-field UV/optical telescope that will operate in the 170-600 nm band and provide 0".3 positions and optical finding charts. Redshift determinations will be made for most bursts. In addition to the primary GRB science, the mission will perform a hard X-ray survey to a sensitivity of similar to1 mcrab (similar to2x10(-11) ergs cm(-2) s(-1) in the 15-150 keV band), more than an order of magnitude better than HEAO 1 A-4. A flexible data and operations system will allow rapid follow-up observations of all types of high-energy transients, with rapid data downlink and uplink available through the NASA TDRSS system. Swift transient data will be rapidly distributed to the astronomical community, and all interested observers are encouraged to participate in follow-up measurements. A Guest Investigator program for the mission will provide funding for community involvement. Innovations from the Swift program applicable to the future include (1) a large-area gamma-ray detector using the new CdZnTe detectors, (2) an autonomous rapid-slewing spacecraft, (3) a multiwavelength payload combining optical, X-ray, and gamma-ray instruments, (4) an observing program coordinated with other ground-based and space-based observatories, and (5) immediate multiwavelength data flow to the community. The mission is currently funded for 2 yr of operations, and the spacecraft will have a lifetime to orbital decay of similar to8 yr