Neutron Star Radius-to-mass Ratio from Partial Accretion Disc Occultation as Measured through Fe Kα\alpha Line Profiles

We present a new method to measure the radius-to-mass ratio (R/M) of weakly magnetic, disc-accreting neutron stars by exploiting the occultation of parts of the inner disc by the star itself. This occultation imprints characteristic features on the X-ray line profile that are unique and are expected to be present in low mass X-ray binary systems seen under inclinations higher than ~65 degrees. We analyse a NuSTAR observation of a good candidate system, 4U 1636-53, and find that X-ray spectra from current instrumentation are unlikely to single out the occultation features owing to insufficient signal-to-noise. Based on an extensive set of simulations we show that large-area X-ray detectors of the future generation could measure R/M to ~2{\div}3% precision over a range of inclinations. Such is the precision in radius determination required to derive tight constraints on the equation of state of ultradense matter and it represents the goal that other methods too aim to achieve in the future.Comment: 17 pages, 8 figures; this is a pre-print edition of an article that has been accepted for publication in the Astrophysical Journa

Neutron star radius-To-mass ratio from partial accretion disk occultation as measured through fe kα line profiles

We present a new method to measure the radius-To-mass ratio (R/M) of weakly magnetic, disk-Accreting neutron stars by exploiting the occultation of parts of the inner disk by the star itself. This occultation imprints characteristic features on the X-ray line profile that are unique and are expected to be present in low-mass X-ray binary systems seen under inclinations higher than ∼65°. We analyze a Nuclear Spectroscopic Telescope Array observation of a good candidate system, 4U 1636-53, and find that X-ray spectra from current instrumentation are unlikely to single out the occultation features owing to insufficient signal-To-noise. Based on an extensive set of simulations we show that large-Area X-ray detectors of the future generation could measure R/M to ∼2 ÷ 3% precision over a range of inclinations. Such is the precision in radius determination required to derive tight constraints on the equation of state of ultradense matter and it represents the goal that other methods also aim to achieve in the future

The Large Observatory for x-ray timing

The Large Observatory For x-ray Timing (LOFT) was studied within ESA M3 Cosmic Vision framework and participated in the final down-selection 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 supra-nuclear densities in the interior of neutron stars. The science payload is based on a Large Area Detector (LAD, 10 m2 effective area, 2-30 keV, 240 eV spectral resolution, 1° collimated field of view) and a WideField 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: a status update

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, >8m2 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

Extreme amplification regimes of the Schwarzschild gravitational lens

We investigated a complete set of relativistic images of a small source located at an arbitrary distance from a Schwarzschild black hole gravitational lens. This paper offers a description of a simple and efficient fully relativistic method for calculating the bolometric intensity amplification. We focused our analysis primarily on sources located at small radii and close angular distance from the caustic line, both behind and in front of the compact lens. We term the corresponding large deflection regime ‘extreme lensing’. We approximated the regime of fully-relativistic, extreme amplification of point sources by simple analytical formulae valid over a wide range of source distances. Using such approximations, we also derived formulae for the maximum amplification of extended sources close to or intercepted by the caustic line. Simple analytical approximations of the time delay between the brightest consecutive images in extreme amplification regimes are also presented

SUITE EN DO MINEUR POUR GRAND ORCHESTRE, OP. 14 / Otakar OSTRCIL ; l'Orchestre Philharmonique tchèque dir. Karl ANCERL. ETE - Poème Symphonique "op. 23" / Otakar OSTRCIL ; l'Orchestre symphonique de la Radio de Brno dir. Bretislav BAKALA

BnF-Partenariats, Collection sonore - BelieveContient une table des matière

Water-in-oil microemulsions versus emulsions as carriers of hydroxytyrosol: an in vitro gastrointestinal lipolysis study using the pHstat technique

Water-in-oil (W/O) microemulsions and emulsions based on medium chain triglycerides (MCT) were successfully formulated with the addition of emulsifiers and used as encapsulation matrices for hydroxytyrosol (HT), an antioxidant naturally found in extra virgin olive oil. The digestibility of these edible W/O dispersions by recombinant dog gastric lipase (rDGL) and porcine pancreatic lipase (PPL) was then tested at different pH values using a pHstat device. rDGL and PPL displayed a much lower activity on the W/O microemulsion than that on the W/O emulsion and MCT alone. This was explained by the presence of higher amounts of emulsifiers (4.9% w/w lecithin and monoglycerides) in the composition of W/O microemulsions compared to W/O emulsions (1.3% w/w emulsifiers). These surfactants also induced a shift of maximum lipase activity towards lower pH values, which usually reflects the competition between surfactants and lipases for binding at the lipid-water interface. rDGL and PPL were then used consecutively in a two-step digestion model mimicking the conditions found in the human gastrointestinal tract. Direct titration and back-titration of free fatty acids allowed the continuous estimation of lipolysis rates under both gastric and duodenal conditions. Gastric lipolysis of W/O microemulsions was reduced 6 to 9-fold compared to W/O emulsions. This inhibition had a major impact on the overall lipolysis, although duodenal lipolysis was less affected by the dispersion type. The presence of HT had also some minor effects on lipolysis rates