eXTP is a science mission designed to study the state of matter under extreme conditions of density, gravity and magnetism. Primary goals are the determination of the equation of state of matter at supra-nuclear density, the measurement of QED effects in highly magnetized star, and the study of accretion in the strong-field regime of gravity. Primary targets include isolated and binary neutron stars, strong magnetic field systems like magnetars, and stellar-mass and supermassive black holes. The mission carries a unique and unprecedented suite of state-of-the-art scientific instruments enabling for the first time ever the simultaneous spectral-timing-polarimetry studies of cosmic sources in the energy range from 0.5-30 keV (and beyond). Key elements of the payload are: the Spectroscopic Focusing Array (SFA) - a set of 11 X-ray optics for a total effective area of ∼0.9 m<sup>2</sup> and 0.6 m<sup>2</sup> at 2 keV and 6 keV respectively, equipped with Silicon Drift Detectors offering <180 eV spectral resolution; the Large Area Detector (LAD) - a deployable set of 640 Silicon Drift Detectors, for a total effective area of ∼3.4 m<sup>2</sup>, between 6 and 10 keV, and spectral resolution better than 250 eV; the Polarimetry Focusing Array (PFA) – a set of 2 X-ray telescope, for a total effective area of 250 cm<sup>2</sup> at 2 keV, equipped with imaging gas pixel photoelectric polarimeters; the Wide Field Monitor (WFM) - a set of 3 coded mask wide field units, equipped with position-sensitive Silicon Drift Detectors, each covering a 90 degrees x 90 degrees field of view. The eXTP international consortium includes major institutions of the Chinese Academy of Sciences and Universities in China, as well as major institutions in several European countries and the United States. The predecessor of eXTP, the XTP mission concept, has been selected and funded as one of the so-called background missions in the Strategic Priority Space Science Program of the Chinese Academy of Sciences since 2011. The strong European participation has significantly enhanced the scientific capabilities of eXTP. The planned launch date of the mission is earlier than 2025.
The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, >8m<sup>2</sup> effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.
The Large Observatory For x-ray Timing (LOFT) was studied within ESA M3 Cosmic Vision framework and participated in the final downselection for a launch slot in 2022-2024. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument, LOFT will study the behaviour of matter under extreme conditions, such as the strong gravitational field in the innermost regions of accretion flows close to black holes and neutron stars, and the supranuclear densities in the interior of neutron stars. The science payload is based on a Large Area Detector (LAD, 10 m<sup>2 </sup> effective area, 2-30 keV, 240 eV spectral resolution, 1° collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g. GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the status of the mission at the end of its Phase A study.
The LOFT mission concept is one of four candidates selected by ESA for the M3 launch opportunity as Medium Size missions of the Cosmic Vision programme. The launch window is currently planned for between 2022 and 2024. LOFT is designed to exploit the diagnostics of rapid X-ray flux and spectral variability that directly probe the motion of matter down to distances very close to black holes and neutron stars, as well as the physical state of ultradense matter. These primary science goals will be addressed by a payload composed of a Large Area Detector (LAD) and a Wide Field Monitor (WFM). The LAD is a collimated (<1 degree field of view) experiment operating in the energy range 2-50 keV, with a 10 m<sup>2</sup> peak effective area and an energy resolution of 260 eV at 6 keV. The WFM will operate in the same energy range as the LAD, enabling simultaneous monitoring of a few-steradian wide field of view, with an angular resolution of <5 arcmin. The LAD and WFM experiments will allow us to investigate variability from submillisecond QPO’s to yearlong transient outbursts. In this paper we report the current status of the project.
The X-ray sky in high time resolution holds the key to a number of observables related to fundamental physics,
inaccessible to other types of investigations, such as imaging, spectroscopy and polarimetry. Strong gravity effects, the
measurement of the mass of black holes and neutron stars, the equation of state of ultradense matter are among the
objectives of such observations. The prospects for future, non-focused X-ray timing experiments after the exciting age of
RXTE/PCA are very uncertain, mostly due to the technological limitations that need to be faced to realize experiments
with effective areas in the range of several square meters, meeting the scientific requirements. We are developing large-area
monolithic Silicon drift detectors offering high time and energy resolution at room temperature, with modest
resources and operation complexity (e.g., read-out) per unit area. Based on the properties of the detector and read-out
electronics we measured in laboratory, we built a concept for a realistic unprecedented large mission devoted to X-ray
timing in the energy range 2-30 keV. We show that effective areas in the range of 10-15 square meters are within reach,
by using a conventional spacecraft platform and launcher.
XEUS has been recently selected by ESA for an assessment study. XEUS is a large mission candidate for the
Cosmic Vision program, aiming for a launch date as early as 2018. XEUS is a follow-on to ESA's Cornerstone
X-Ray Spectroscopy Mission (XMM-Newton). It will be placed in a halo orbit at L2, by a single Ariane 5 ECA,
and comprises two spacecrafts. The Silicon pore optics assembly of XEUS is contained in the mirror spacecraft
while the focal plane instruments are contained in the detector spacecraft, which is maintained at the focus of the
mirror by formation flying. The main requirements for XEUS are to provide a focused beam of X-rays with an
effective aperture of 5 m<sup>2</sup> at 1 keV, 2 m<sup>2</sup> at 7 keV, a spatial resolution better than 5 arcsec, a spectral resolution
ranging from 2 to 6 eV in the 0.1-8 keV energy band, a total energy bandpass of 0.1-40 keV, ultra-fast timing,
and finally polarimetric capabilities. The High Time Resolution Spectrometer (HTRS) is one of the five focal
plane instruments, which comprises also a wide field imager, a hard X-ray imager, a cryogenic spectrometer,
and a polarimeter. The HTRS is unique in its ability to cope with extremely high count rates (up to 2 Mcts/s),
while providing sub-millisecond time resolution and good (CCD like) energy resolution. In this paper, we focus
on the specific scientific objectives to be pursued with the HTRS: they are all centered around the key theme
"Matter under extreme conditions" of the Cosmic Vision science program. We demonstrate the potential of the HTRS observations to probe strong gravity and matter at supra-nuclear densities. We conclude this paper by
describing the current implementation of the HTRS in the XEUS focal plane.
We present a brief review of time-varying spectral analysis and we discuss the applicability of the methods to the case of x-ray bursts where it is known that there are time-varying frequency components. A preliminary analysis is done on x-ray burst the experimental data. Two methods are presented to estimat the instanteous frequency and both methods give approximately the same results.
Accreting binaries containing a black hole are stellar systems composed of a normal star and a black hole.
Because of the strong gravitational pull of the black hole, matter is removed from the companion star and falls
into the compact object. In falling, it forms an accretion disk of gas that spirals towards the center, heating
up and emitting in X rays. The physics of such a structure is extremely complex and can be studied through
observations with X-ray satellites. The time series derived from X-ray observations of bright black-hole binaries
in the Galaxy show a complex phenomenology. Broad noise components with a variability of up to ~40% are
observed, as well as quasi-periodic features on time scales from 100 seconds down to a few milliseconds. The
characteristic frequencies of the di.erent components can change on very short time scales. However, some
of these signals are elusive as they are very weak and are drowned in intrinsic and instrumental noise. The
physical nature of these signals is still largely unknown, but it is clear that they originate from gas orbiting a
few kilometers from the central black hole and accreting onto it. In addition of being important for the study
of the accretion of matter onto a black hole, these observational properties constitute a unique probe for testing
General Relativity in the strong field regime. I review the current observational status as well as the techniques used to study these signals.