We use frequency-resolved spectroscopy to examine the energy spectra of the prominent low frequency QPO and its harmonic in GX 339-4. We track the evolution of these spectra as the source makes a transition from a bright low/hard to hard intermediate
state. In the hard/intermediate states, the QPO and time averaged spectra are similar and the harmonic is either undetected or similar to the QPO. By contrast, in the softer states the harmonic is dramatically softer than the QPO spectrum and the time averaged spectrum, and the QPO spectrum is dramatically harder than the time averaged spectrum. Clearly, the existance of these very different spectral shaped components mean that the time-averaged spectra are complex. We use the frequency resolved spectra to better constrain the model components, and find that the data are consistent with a time-averaged spectrum which has an additional low temperature, optically thick Comptonisation component. The harmonic can be described by this additional component alone, while the QPO spectrum is similar to that of the hard Comptonisation and its reflection. Neither QPO nor harmonic show signs of the disc component even when it is strong in the time averaged spectrum. While the similarity between the harmonic and QPO spectra in the intermediate state can be produced from the angular dependence of Compton scattering in a single region, this cannot explain the dramatic differences seen in the soft state. Instead, we propose that the soft Compton region is located predominantly above the disc while the hard Compton is from the hotter inner flow. Our results therefore point to multiple possible mechanisms for producing harmonic features in the power spectrum. The dominant mechanism in a given observation is likely a function of both inclination angle and inner disc radius.
At high luminosities black hole binaries show spectra with a strong disc component accompanied by an equally strong tail where at least some of the electrons are non-thermal. We reanalyze the simultaneous ASCA-RXTE-OSSE data from the 1998 outburst of
XTE J1550-564, which span 0.7-1000 keV and remain the best data available of a black hole binary in this state. We reassess the importance of electron-positron pair production using a realistically high value of the source compactness for the first time. The lack of an observable annihilation line together with the observed gamma-ray flux beyond 511 keV constrains the maximum electron Lorentz factor to be leq 10 and the slope of the injected electrons to leq 2.5. We also use the fast (10-50 Hz) variability spectrum to constrain the spatial dependence of the electron heating and acceleration. We find that the spectrum of the fast variability is consistent with being fully thermal, so that the observed non-thermal emission is produced from further out in the flow.
The broad energy range spanned by ASTRO-H instruments, from ~0.3 to 600 keV, with its high spectral resolution calorimeter and sensitive hard X-ray imaging, offers unique opportunities to study black holes and their environments. The ability to measu
re polarization is particularly novel, with potential sources including blazars, Galactic pulsars and X-ray binaries. In this White Paper, we present an overview of the synergistic instrumental capabilities and the improvements over prior missions. We also show how ASTRO-H fits into the multi-wavelength landscape. We present in more detail examples and simulations of key science ASTRO-H can achieve in a typical 100 ksec observation when data from all four instruments are combined. Specifically, we consider observations of black-hole source (Cyg X-1 and GRS 1915+105), blazars (Mrk 421 and Mrk 501), a quasar (3C 273), radio galaxies (Centaurus A and 3C 120), and active galaxies with a strong starburst (Circinus and NGC 4945). We will also address possible new discoveries expected from ASTRO-H.
There is still 10-20% uncertainty on the neutron star (NS) mass-radius relation. These uncertainties could be reduced by an order of magnitude through an unambiguous measure of M/R from the surface redshift of a narrow line, greatly constraining the
Equation of State for ultra-dense material. It is possible that the SXS on ASTRO-H can detect this from an accreting neutron star with low surface velocity in the line of sight i.e. either low inclination or low spin. Currently there is only one known low inclination LMXB, Ser X-1, and one known slow spin LMXB, J17480-2446 in Terzan 5. Ser X-1 is a persistent source which is always in the soft state (banana branch), where the accreting material should form a equatorial belt around the neutron star. A pole-on view should then allow the NS surface to be seen directly. A 100 ks observation should allow us to measure M/R if there are any heavy elements in the photosphere at the poles. Conversely, J17480-2446 in Terzan 5 is a transient accretion powered millisecond pulsar, where the accreting material is collimated onto the magnetic pole in the hard (island) state (L_x < 0.1 L_Edd). The hotspot where the shock illuminates the NS surface is clearly seen in this state. A 100 ks ToO observation of this (or any other similarly slow spin system) in this state, may again allow the surface redshift to be directly measured. (abstract continues)
RE J2248-511 is one of only 14 non-blazar AGN detected in the far ultraviolet by the ROSAT Wide Field Camera implying a large ultrasoft X-ray flux. This soft X-ray excess is strongly variable on year timescales, a common property of Narrow Line Seyfe
rt 1s, yet its optical linewidths classify this source as a broad-lined Seyfert 1. We use four nearly simultaneous optical--X-ray SEDs spanning 7 years to study the spectral shape and long term variability of RE J2248-511. Here we show that the continuum SED for the brightest epoch dataset is consistent with the mean SED of a standard quasar, and matches well to that from an XMM-SDSS sample of AGN with <M/M_Sun> ~ 10^8 and <L/L_Edd> ~ 0.2. All the correlated optical and soft X-ray variability can be due entirely to a major absorption event. The only remarkable aspect of this AGN is that there is no measurable intrinsic X-ray absorption column in the brightest epoch dataset. The observed FUV flux is determined by the combination of this and the fact that the source lies within a local absorption `hole. RE J2248-511, whose variable, ultrasoft X-ray flux once challenged its BLS1 classification, demonstrates that characterisation of such objects requires multi-epoch, multi-wavelength campaigns.
We extract the spectra of the fastest variability (above 10 Hz) from the black hole XTE J1550-564 during a transition from hard to soft state on the rise to outburst. We confirm previous results that the rapid variability contains no significant disc
component despite this being strongly present in the total spectrum of the softer observations. We model ionised reflection significantly better than previous work, and show that this is also suppressed in the rapid variability spectrum compared to the total emission. This is consistent with the fast variability having its origin in a hot inner flow close to the black hole rather than in the accretion disc or in a corona above it. However, the rapid variability spectrum is not simply the same as the total Comptonised emission. It is always significantly harder, by an amount which increases as the spectrum softens during the outburst. This adds to evidence from time lags that the Comptonisation region is inhomogeneous, with harder spectra produced closest to the black hole, the same region which produces the fastest variability.
We use XMM-Newton and Swift data to study spectral variability in the ultraluminous X-ray source (ULX), Holmberg IX X-1. The source luminosity varies by a factor 3-4, giving rise to corresponding spectral changes which are significant, but subtle, an
d not well tracked by a simple hardness ratio. Instead, we co-add the Swift data in intensity bins and do full spectral fitting with disc plus thermal Comptonisation models. All the data are well-fitted by a low temperature, optically thick Comptonising corona, and the variability can be roughly characterised by decreasing temperature and increasing optical depth as the source becomes brighter, as expected if the corona is becoming progressively mass loaded by material blown off the super-Eddington inner disc. This variability behaviour is seen in other ULX which have similar spectra, but is opposite to the trend seen in ULX with much softer spectra. This supports the idea that there are two distinct physical regimes in ULXs, where the spectra go from being dominated by a disc-corona to being dominated by a wind.
We use the photoionisation code Cloudy to determine both the location and the kinematics of the optical forbidden, high ionisation line (hereafter, FHIL) emitting gas in the narrow line Seyfert 1 galaxy Ark 564. The results of our models are compared
with the observed properties of these emission lines to produce a physical model that is used to explain both the kinematics and the source of this gas. The main features of this model are that the FHIL emitting gas is launched from the putative dusty torus and is quickly accelerated to its terminal velocity of a few hundred km/s. Iron-carrying grains are destroyed during this initial acceleration. This velocity is maintained by a balance between radiative forces and gravity in this super-Eddington source. Eventually the outflow is slowed at large radii by the gravitational forces of and interactions with the host galaxy. In this model, FHIL emission traces the transition between the AGN and bulge zones of influence.
abridged: We use XSCORT, together with the hydrodynamic accretion disc wind simulation from Proga & Kallman (2004), to calculate the impact that the accretion disk wind has on the X-ray spectrum from a 1E8 solar mass black hole Active Galactic Nuclei
(AGN) accreting at 0.5 L/L_Edd. The properties of the resulting spectra depend on viewing angle and clearly reflect the distinct regions apparent in the original hydrodynamic simulation. Very equatorial lines-of-sight (l.o.s) are dominated by Compton scattering and nearly-neutral absorption. Polar l.o.s result in largely featureless spectra. Finally, l.o.s that intersect the transition region between these extremes have a wide range of absorption features imprinted on the spectrum. Both polar and transition region l.o.s produce spectra that show highly-ionized, blue-shifted, Fe absorption features that are qualitatively similar to features observed in the X-ray spectra of a growing number of AGN. The spectra presented here clearly demonstrate that current simulations of line driven AGN accretion disk winds cannot reproduce the smooth soft X-ray excess. Furthermore, they predict that high accretion rate (L/L_Edd) AGN are likely to be strongly affected by obscuration, in sharp contrast to the clean picture that is generally assumed, based on the observed relation between the opening angle of the molecular torus and AGN luminosity.
