K. O. Mason

Constraining the black hole mass and accretion rate in the narrow-line Seyfert 1 galaxy RE J1034+396

We present a comprehensive study of the spectrum of the narrow-line Seyfert 1 (NLS1) galaxy RE J1034+396, summarizing the information obtained from the optical to X-rays with observations from the William Herschel 4.2 m Telescope, the Hubble Space Telescope, the Extreme Ultraviolet Explorer, ROSAT, ASCA, and BeppoSAX. The BeppoSAX spectra reveal a soft component which is well represented by two blackbodies with kTeff = 60 and 160 eV, mimicking that expected from a hot, optically thick accretion disk around a low-mass black hole. This is borne out by our modeling of the optical-to-X-ray nuclear continuum, which constrains the physical parameters of a NLS1 for the first time. The models demonstrate that RE J1034+396 is likely to be a system with a nearly edge-on accretion disk (60°-75° from the disk axis), accreting at nearly Eddington rates (0.3-0.7LEdd) onto a low-mass black hole (Mbh ~ 2-10 × 106 M☉). This is consistent with the hypothesis that NLS1s are Seyfert-scale analogies of galactic black hole candidates. The unusually high temperature of the big blue bump reveals a flat power-law-like continuum in the optical/UV which is consistent with an extrapolation to the hard X-ray power law, and which we speculate may be similar to the continuum component observed in BL Lac objects in their quiescent periods. From the BeppoSAX and ASCA data, we find that the slope of the hard X-ray power law depends very much on the form of the soft component which is assumed. For our best-fitting models, it lies somewhere between α = 0.7 and 1.3 and thus may not be significantly softer than active galactic nuclei in general.

XMM-Newton first-light observations of the Hickson galaxy group 16

This paper presents the XMM-Newton first-light observations of the Hickson-16 compact group of galaxies. Groups are possibly the oldest large-scale structures in the Universe, pre-dating clusters of galaxies, and are highly evolved. This group of small galaxies, at a redshift of 0.0132 (or 80 Mpc) is exceptional in the having the highest concentration of starburst or AGN activity in the nearby Universe. So it is a veritable laboratory for the study of the relationship between galaxy interactions and nuclear activity. Previous optical emission line studies indicated a strong ionising continuum in the galaxies, but its origin, whether from starbursts, or AGN, was unclear. Combined imaging and spectroscopy with the EPIC X-ray CCDs unequivocally reveals a heavily obscured AGN and a separately identified thermal (starburst) plasma, in NGC 835, NGC 833 and NGC 839. NGC 838 shows only starburst thermal emission. Starbursts and AGN can evidently coexist in members of this highly evolved system of merged and merging galaxies, implying a high probability for the formation of AGN as well as starbursts in post-merger galaxies.

XEUS-the X-ray evolving universe spectroscopy mission

XEUS is under study by ESA as part of the Horizon 2000+ program to utilize the International Space Station (ISS) for astronomical applications. XEUS will be a long-term X-ray observatory with an initial mirror area of 6 m2 at 1 keV that will be grown to 30 m2 following a visit to the ISS. The 1 keV spatial resolution is expected to be 2–5″ HEW. XEUS will consist of separate detector and mirror spacecraft aligned by active control to provide a focal length of 50 m. A new detector spacecraft, complete with the next generation of instruments, will also be added after visiting the ISS. The limiting sensitivity will then be ∼4×10−18 erg cm−2 s−1 around 250 times better than XMM. The properties of a 350 eV (rest-frame) equivalent width Fe line from a 1044 erg s−1 AGN will be measurable out to z=10, paving the way for detailed spectroscopic X-ray studies of some of the earliest known objects.XEUS is under study by ESA as part of the Horizon 2000+ program to utilize the International Space Station (ISS) for astronomical applications. XEUS will be a long-term X-ray observatory with an initial mirror area of 6 m2 at 1 keV that will be grown to 30 m2 following a visit to the ISS. The 1 keV spatial resolution is expected to be 2–5″ HEW. XEUS will consist of separate detector and mirror spacecraft aligned by active control to provide a focal length of 50 m. A new detector spacecraft, complete with the next generation of instruments, will also be added after visiting the ISS. The limiting sensitivity will then be ∼4×10−18 erg cm−2 s−1 around 250 times better than XMM. The properties of a 350 eV (rest-frame) equivalent width Fe line from a 1044 erg s−1 AGN will be measurable out to z=10, paving the way for detailed spectroscopic X-ray studies of some of the earliest known objects.

XMM–Newton spectroscopy of high-redshift quasars

We present XMM-Newton X-ray spectra and optical photometry of four high-redshift (z = 2.96-3.77) quasars, [HB89] 0438-436, [HB89] 2000-330, [SP89] 1107+487 and RX J122135.6+280613; of these four objects, the first two are radio-loud and the last two are radio-quiet. Model fits require only a power law with Galactic absorption in each case; additional intrinsic absorption is also needed for [HB89] 0438-436 and RX J122135.6+280613. The spectra are hard (Γ ∼ 1.7 for [HB89] 0438-436, [HB89] 2000-330 and ∼1.4 for RX J122135.6+280613), with the exception of [SP89] 1107+487, which is softer (r ∼ 2.0); the combined Galactic and intrinsic absorption of lower-energy X-rays in the last of the sources is much less significant than in the other three. The two intrinsically unabsorbed sources have greater optical fluxes relative to the X-ray contributions at the observed energies. While there is no need to include reflection or iron line components in the models, our derived upper limits (99 per cent confidence) on these parameters are not stringent; the absence of these features, if confirmed, may be explained in terms of the high power-law contribution and/or a potentially lower albedo as a result of the low disc temperature. However, we note that the power-law spectrum can be produced via mechanisms other than the Comptonization of accretion disc emission by a corona; given that all four of these quasars are radio sources at some level, we should also consider the possibility that the X-ray emission originates, at least partially, in a jet.

The UV spectrum of the narrow-line Seyfert 1 galaxy, REJ1034+396

We present UV spectroscopy of RE1034+396, taken with the Faint Object Spectrograph on the Hubble Space Telescope. With a spectral resolution of ~1-2A FWHM and a typical S/N of ~15 per diode, this is one of the first detailed UV spectra of an object in the narrow-line Seyfert 1 (NLS1) class. The spectrum probes the physics and kinematics of the high-ionization and coronal line gas, and the strength and form of the big blue bump component in the UV. We detect many emission lines, including Lyman alpha, CIV1549, HeII1640, CIII]1909 and MgII2798. We also identify a feature at 2647A (in the rest-frame) with highly-ionized iron [FeXI]2649; a line of the same species ([FeXI]7892) has also been seen in the optical spectrum. The velocity widths of the UV lines are relatively narrow (FWHM<2000 km/s) and similar to those of the optical lines, which suggests that all line emission in REJ1034+396, ie. including that of high- and low-ionization species and the forbidden lines, may be dominated by an intermediate-velocity (FWHM~1000 km/s), intermediate-density (log Ne~7.5 cm-3) region of gas. The slope of the UV continuum (alpha~0.9) is soft (ie. red) relative to quasars and the UV-to-soft X-ray flux ratio is unusually low implying that the big blue bump component is very weak in the UV. The present epoch UV to soft X-ray continuum is consistent with earlier data, demonstrating that this extreme big blue bump component is also very stable, unlike many other NLS1s which show extreme patterns of variability.

The Variable Iron Line in Cygnus X-3

Cygnus X-3 was observed with the GSPC on board EXOSAT on several occasions, one observation lasting for 7 orbital cycles. The width W and centroid energy E of the iron emission feature near 6.7 keV show a smooth, correlated, sinusoidal-type modulation, the iron line being widest and E being lowest just before X-ray maximum. The line profile may show a low-energy wing, but apart from this does not deviate strongly from a symmetric, Gaussian-type shape. The continuum at higher energies than the line is not completely smooth, but shows ‘bumps’ which remain stable in time. Two possible explanations are discussed for the correlated variation of E and W as a function of orbital phase.

Multi-Wavelength Observations with the XMM Observatory

A major feature of the planning of X-ray observations has been the extensive coordination of ground-based facilities in order to obtain simultaneous observations at optical wavelengths. This was recognized by ESA in the definition of the model payload for XMM, which included an optical/UV telescope, the XMM Optical Monitor, as one of the three instruments on board.

Accretion disc evolution in cataclysmic variables (the 1988 international time project in La Palma

A summary of data collected during a sixty night international campaign devoted to cataclysmic variables is presented.

Short-timescale variability in cataclysmic binaries

Rapid variability, including flickering and pulsations, has been detected in cataclysmic binaries at optical and x-ray frequencies. In the case of the novalike variable TT Arietis, simultaneous observations reveal that the x-ray and optical flickering activity is strongly correlated, while short period pulsations are observed that occur at the same frequencies in both wavelength bands.