Showing papers by "Netherlands Institute for Space Research published in 2002"
TL;DR: In this paper, a high spectral resolution observation of the diffuse X-ray background in the 60-1000 eV energy range has been made using an array of 36 1 mm 2 microcalorimeters flown on a sounding rocket.
Abstract: A high spectral resolution observation of the diffuse X-ray background in the 60–1000 eV energy range has been made using an array of 36 1 mm 2 microcalorimeters flown on a sounding rocket. Detector energy resolution ranged from 5 to 12 eV FWHM, and a composite spectrum of � 1 sr of the background centered at l ¼ 90 � , b ¼þ 60 � was obtained with a net resolution of � 9 eV. The target area includes bright 1 keV regions but avoids Loop I and the North Polar Spur. Lines of C vi ,O vii, and O viii are clearly detected with intensities of 5:4 � 2:3, 4:8 � 0:8, and 1:6 � 0:4 photons cm � 2 s � 1 sr � 1 , respectively. The oxygen lines alone account for a majority of the diffuse background observed in the ROSAT R4 band that is not due to resolved extragalactic discrete sources. We also have a positive detection of the Fe-M line complex near 70 eV at an intensity consistent with previous upper limits that indicate substantial gas-phase depletion of iron. We include a detailed description of the instrument and its detectors. Subject headings: instrumentation: detectors — instrumentation: spectrographs — intergalactic medium — space vehicles: instruments — X-rays: diffuse background — X-rays: ISM
380 citations
TL;DR: The discovery of significant absorption lines in the spectra of 28 bursts of the low-mass X-ray binary EXO0748-676 is reported, which is completely consistent with models of neutron stars composed of normal nuclear matter, while it excludes some models in which the neutron stars are made of more exotic matter.
Abstract: The fundamental properties of neutron stars provide a direct test of the equation of state of cold nuclear matter, a relationship between pressure and density that is determined by the physics of the strong interactions between the particles that constitute the star. The most straightforward method of determining these properties is by measuring the gravitational redshift of spectral lines produced in the neutron star photosphere1. The equation of state implies a mass–radius relation, while a measurement of the gravitational redshift at the surface of a neutron star provides a direct constraint on the mass-to-radius ratio. Here we report the discovery of significant absorption lines in the spectra of 28 bursts of the low-mass X-ray binary EXO0748-676. We identify the most significant features with the Fe xxvi and xxv n = 2–3 and O viii n = 1–2 transitions, all with a redshift of z = 0.35, identical within small uncertainties for the respective transitions. For an astrophysically plausible range of masses (M ≈ 1.3–2.0 solar masses; refs 2–5), this value is completely consistent with models of neutron stars composed of normal nuclear matter, while it excludes some models6,7 in which the neutron stars are made of more exotic matter.
380 citations
TL;DR: In this paper, a high spectral resolution observation of the diffuse X-ray background in the 60 - 1000 eV energy range has been made using an array of thirty-six 1 mm^2 micro-calorimeters flown on a sounding rocket.
Abstract: A high spectral resolution observation of the diffuse X-ray background in the 60 - 1000 eV energy range has been made using an array of thirty-six 1 mm^2 micro-calorimeters flown on a sounding rocket. Detector energy resolution ranged from 5-12 eV FWHM, and a composite spectrum of ~ 1 steradian of the background centered at l = 90, b = +60 was obtained with a net resolution of ~ 9 eV. The target area includes bright 1/4 keV regions, but avoids Loop I and the North Polar Spur. Lines of C VI, O VII, and O VIII are clearly detected with intensities of 5.4 +/- 2.3, 4.8 +/- 0.8, and 1.6 +/- 0.4 photons cm^-2 s^-1 sr^-1, respectively. The oxygen lines alone account for a majority of the diffuse background observed in the ROSAT R4 band that is not due to resolved extragalactic discrete sources. We also have a positive detection of the Fe-M line complex near 70 eV at an intensity consistent with previous upper limits that indicate substantial gas phase depletion of iron. We include a detailed description of the instrument and its detectors.
15 citations
Indian Space Research Organisation1, Southwest Research Institute2, Marshall Space Flight Center3, University of Michigan4, University of Liège5, University of Kansas6, University of Wyoming7, California Institute of Technology8, University of California, Berkeley9, Netherlands Institute for Space Research10, University of Virginia11, Massachusetts Institute of Technology12, Boston University13, Pennsylvania State University14, Imperial College London15, Max Planck Society16
TL;DR: A brief review of the x-ray observations on each of the planetary bodies and discuss their characteristics and proposed source mechanisms can be found in this article, where the authors also discuss the characteristics and sources of the X-ray energy.
Abstract: A wide variety of solar system bodies are now known to radiate in the soft x-ray energy ( 10 keV) x-rays mainly result from the electron bremsstrahlung process. In this paper we present a brief review of the x-ray observations on each of the planetary bodies and discuss their characteristics and proposed source mechanisms. 1. INTRODUCTION The usually-defined range of x-ray photons spans 0.1-100 keV. Of this wide energy extent the soft x-ray energy band (<5 keV) is an important spectral regime for planetary remote sensing, as a large number of solar system objects are now known to shine at these wavelengths. These include Earth, Moon, Jupiter, Saturn, comets, Venus, Galilean satellites, Mars, Io plasma torus, and (of course) the Sun. Since Earth's thick atmosphere efficiently absorbs x-ray radiation at lower altitudes (<30 km, even for hard x-rays), x-rays can only be observed from space by high-altitude balloon-, rocket-, and satellite-based instruments. But to observe most of the soft x-ray band one has to be above ~100 km from Earth's surface. Terrestrial x-rays were discovered in the 1950s. The launch of the first x-ray satellite UHURU in 1970 marked the beginning of satellite-based x-ray astronomy. Subsequently launched x-ray observatories - Einstein, and particularly Rontgensatellit (ROSAT), made important contributions to planetary x-ray studies. With the advent of th el a sn dm p ic x- ry b -Chandra and XMM-Newton - the field of planetary x-ray astronomy is advancing at a much faster pace. Earth and Jupiter, as magnetic planets, are observed to emanate strong x-ray emissions from their auroral (polar) regions, thus providing vital information on the nature of precipitating particles and their energization processes in planetary magnetospheres [1,2,3]. X-rays from low latitudes have also been observed on these planets. Saturn sho ul d a p rc ex- y in tm w J ,although the intensity is expected to be weaker. Lunar x-rays have been observed from the sunlit hemisphere; and a small number of x-rays are also seen from the Moon's nightside [4]. Cometary x-rays are now a well-established phenomena; more than a dozen comets have been observed at soft x-ray energies [5,6]. The Chandra X-ray Observatory (CXO) has recently captured soft x-rays from Venus [7,8]. Martian x-rays are expected to be similar to those on Venus. More recently, using CXO [9] have discovered soft x-rays from the inner moons of Jupiter - Io, Europa, and probably Ganymede. The Io Plasma Torus (IPT) was also discovered recently
12 citations