Future X-ray Instruments Research Articles

Timing of accreting neutron stars with future X-ray instruments: towards new constraints on dense matter equation of state

Timing of accreting neutron stars with future X-ray instruments: towards new constraints on dense matter equation of state

Gravitational-wave versus x-ray tests of strong-field gravity

Electromagnetic observations of the radiation emitted by an accretion disk around a black hole, as well as gravitational wave observations of coalescing binaries, can be used to probe strong-field gravity. We here compare the constraints that these two types of observations can impose on theory-agnostic, parametric deviations from the Schwarzschild metric. On the gravitational wave side, we begin by computing the leading-order deviation to the Hamiltonian of a binary system in a quasi-circular orbit within the post-Newtonian approximation, given a parametric deformation of the Schwarzschild metrics of each binary component. We then compute the leading-order deviation to the gravitational waves emitted by such a binary in the frequency domain, assuming purely Einsteinian radiation-reaction. We compare this model to the LIGO-Virgo collaboration gravitational wave detections and place constraints on the metric deformation parameters, concluding with an estimate of the constraining power of aLIGO at design sensitivity. On the electromagnetic side, we first simulate observations with current and future x-ray instruments of an x-ray binary with a parametrically-deformed Schwarzschild black hole, and we then estimate constraints on the deformation parameters using these observations. We find that current gravitational wave observations have already placed constraints on the metric deformation parameters than are slightly more stringent than what can be achieved with current x-ray instruments. Moreover, future gravitational wave observations with aLIGO at design sensitivity by 2026 will be even more stringent, becoming stronger than constraints achievable with future ATHENA x-ray observations before it flies in 2034.

X-ray extinction from interstellar dust

Aims. We present a study on the prospects of observing carbon, sulfur, and other lower abundance elements (namely Al, Ca, Ti, and Ni) present in the interstellar medium using future X-ray instruments. We focus in particular on the detection and characterization of interstellar dust along the lines of sight. Methods. We compared the simulated data with different sets of dust aggregates, either obtained from past literature or measured by us using the SOLEIL-LUCIA synchrotron beamline. Extinction by interstellar grains induces modulations of a given photolelectric edge, which can be in principle traced back to the chemistry of the absorbing grains. We simulated data of instruments with characteristics of resolution and sensitivity of the current Athena, XRISM, and Arcus concepts. Results. In the relatively near future, the depletion and abundances of the elements under study will be determined with confidence. In the case of carbon and sulfur, the characterization of the chemistry of the absorbing dust will be also determined, depending on the dominant compound. For aluminum and calcium, despite the large depletion in the interstellar medium and the prominent dust absorption, in many cases the edge feature may not be changing significantly with the change of chemistry in the Al- or Ca-bearing compounds. The exinction signature of large grains may be detected and modeled, allowing a test on different grain size distributions for these elements. The low cosmic abundance of Ti and Ni will not allow us a detailed study of the edge features.

X-ray photometry

Abstract I describe a method for synthesizing photometric passbands for use with current and future X-ray instruments. The method permits the standardization of X-ray passbands and thus X-ray photometry between different instruments and missions. The method is illustrated by synthesizing a passband in the XMM–Newton European Photon Imaging Camera pn which is similar to the ROSAT Position Sensitive Proportional Counter 0.5–2 keV band.

Multiwavelength Astronomy and CTA: X-rays

We discuss how future X-ray instruments which are under development can contribute to our understanding of the non-thermal Universe. Much progress has been made in the field of X-ray Astronomy recently, thanks to the operation of modern X-ray telescopes such as Chandra, XMM-Newton, Suzaku, and SWIFT, but more in-depth investigation awaits future missions. These future missions include ASTROSAT, NuSTAR, e-ROSITA, ASTRO-H and GEMS, which will be realized in the next decade, and also much larger projects such as Athena and LOFT, which have been proposed for the 2020’s. All of those are expected to bring a variety of novel observational results regarding astrophysical sources of high-energy particles and radiation, i.e. supernova remnants, neutron stars, stellar-mass black holes, active galaxies, and clusters of galaxies among others. The operation of the future X-ray instruments will proceed in parallel with the operation of Fermi-LAT and the Cherenkov Telescope Array. We emphasize that the synergy between the X-ray and γ-ray observations is particularly important, and that the planned X-ray missions, when in conjunction with the modern γ-ray observatories, will indeed provide a qualitatively better insight into the high-energy Universe.

Probing the very high redshift Universe with gamma-ray bursts: prospects for observations with future X-ray instruments

Gamma-Ray Bursts (GRBs) are the most violent explosions in the Universe. Long duration GRBs are associated with the collapse of massive stars, rivaling their host galaxies in luminosity. The discovery of the most distant spectroscopically confirmed object in the Universe, GRB090423, opened a new window on the high redshift Universe, making it possible to study the cosmic 're-ionization' epoch and the preceding dark ages, as well as the generation of the first stars (Population III) using GRBs. Obviously this enables a wealth of new studies using the near infrared (nIR) characteristics of GRB afterglows. Here we explore a different path, focusing on the next generation of X-ray missions with large area focusing telescopes and fast repointing capabilities. We found that X-ray data can complement nIR observations and for the brightest GRBs can provide an accurate and independent redshift determination. Metallicity studies can also be carried out profitably once the redshift is known. Finally we discuss observational signatures of GRBs arising from Population III stars in the X-ray band.

ON THE PROSPECT OF CONSTRAINING BLACK HOLE SPIN THROUGH X-RAY SPECTROSCOPY OF HOTSPOTS

Future X-ray instrumentation is expected to allow us to significantly improve the constraints derived from the Fe K lines in active galactic nuclei, such as the black hole angular momentum (spin) and the inclination angle of the putative accretion disk. We consider the possibility that measurements of the persistent, time-averaged Fe K line emission from the disk could be supplemented by the observation of a localized flare, or "hotspot," orbiting close to the black hole. Although observationally challenging, such measurements would recover some of the information loss that is inherent to the radially integrated line profiles. We present calculations for this scenario to assess the extent to which, in principle, black hole spin may be measured. We quantify the feasibility of this approach using realistic assumptions about likely measurement uncertainties.

High-redshift X-ray properties of the haloes of simulated disc galaxies

X-ray luminosities and surface brightness profiles of the hot gas haloes of simulated disc galaxies at redshifts z = 0 2 are presented. The galaxies are extracted from fully cosmological simulations and correspond in mass to the Milky Way. We find that the bolometric X-ray luminosities of the haloes decrease by a factor 4 10 from z � 1 to z � 0, reflecting the decrease in the rate at which hot halo gas cools out on to the disc. At all redshifts, most of the emission is found to originate within 10–15 kpc of the disc. When combined with models in which the evolution of disc X-ray luminosity is dominated by X-ray binaries, the predicted halo luminosities at z � 1 show good agreement with constraints from spiral galaxies in Chandra Deep Field data. There is an indication that haloes with a metal abundance of 0.3Z⊙ overpredict observed Xray luminosities at z � 1, suggesting that halo metallicities are lower than this value. Prospects for direct detection of the haloes of Milky Way–sized galaxies with current and future X-ray instrumentation are discussed. It is found that XEUS should be able to single out the halo emission of highly inclined Milky Way–sized disc galaxies out to z � 0.3. For such galaxies in this redshift interval, we estimate a lower limit to the surface density of detectable haloes on the sky of � 10 deg −2 . More generally, owing to their luminosity evolution, the optimum redshifts at which to observe such haloes could be 0.5 < z < 1, depending on their assembly history.