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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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82 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Interstellar X-Ray Absorption Spectroscopy of the Crab Pulsar with the LETGS

We study the interstellar X-ray absorption along the line of sight to the Crab Pulsar. The Crab was observed with the Low Energy Transmission Grating Spectrometer on the Chandra X-ray Observatory, and the pulsar, a point source, produces a full resolution spectrum. The continuum spectrum appears smooth, and we compare its parameters with other measurements of the pulsar spectrum. The spectrum clearly shows absorption edges due to interstellar Ne, Fe, and O. The O edge shows spectral structure that is probably due to O bound in molecules or dust. We search for near-edge structure (EXAFS) in the O absorption spectrum. The Fe L absorption spectrum is largely due to a set of unresolved discrete n=2-3 transitions in neutral or near-neutral Fe, and we analyze it using a new set of dedicated atomic structure calculations, which provide absolute cross sections. In addition to being interesting in its own right, the ISM absorption needs to be understood in quantitative detail in order to derive spectroscopic constraints on possible soft thermal radiation from the pulsar.

Paerels, Frits↗
NASA NTRS2001

Chandra X-Ray Observations of the Anomalous X-Ray Pulsar 1E 2259+58.6

We present X-ray imaging, timing, and phase resolved spectroscopy of the anomalous X-ray pulsar 1E 2259+58.6 using the Chandra X-ray Observatory. Time resolved X-ray spectra show no significant variation as a function of pulsar spin phase. The phase averaged spectrum is well described by a powerlaw plus blackbody model; we find no evidence for spectral features. We derive a spin period. We have detected a halo beyond the central source, possibly due to dust scattering in the ISM (interstellar matter).

Patel, Sandeep K.↗
NASA NTRS2001

Discovery of X-Ray Emission from the Crab Pulsar at Pulse Minimum

The Chandra X-Ray Observatory observed the Crab pulsar using the Low-Energy Transmission Grating with the High-Resolution Camera. Time-resolved zeroth-order images reveal that the pulsar emits X-rays at all pulse phases. Analysis of the flux at minimum - most likely non-thermal in origin - places an upper limit (T(sub infinity) < 2.1 MK) on the surface temperature of the underlying neutron star. In addition, analysis of the pulse profile establishes that the error in the Chandra-determined absolute time is quite small, -0.2 +/- 0.1 ms.

Tennant, Allyn F.↗
NASA NTRS2001

Chandra Observations of the Crab Pulsar as a Function of Pulse Phase

The Chandra X-Ray Observatory was used to observe the Crab Nebula and its pulsar using the LETGS, i.e. the Low-Energy Transmission Grating (LETG) with the High Resolution Camera Spectroscopy detector (HRC-S). Data from the zeroth-order image was utilized to isolate the pulsar from the surrounding nebula and to measure the pulsar emission as a function of pulse phase. HRC timing problems were overcome by developing special techniques to process the data. For the first time, pulsed x-ray emission has been detected at all pulse phases, allowing us to set a new upper limit to the thermal emission from the surface of the neutron star.

Weisskopf, Martin C.↗
NASA NTRS2000

First XMM-Newton Observations of an Isolated Neutron Star: RXJ0720.4-3125

We present the high resolution spectrum of the isolated neutron star RXJ0720.4-3125, obtained with the Reflection Grating Spectrometer on XMM-Newton, complemented with the broad band spectrum observed with the EPIC PN camera. The spectrum appears smooth, with no evidence for strong photospheric absorption or emission features. We briefly discuss the implications of our failure to detect structure in the spectrum.

Paerels, Frits↗
NASA NTRS2000

A High Resolution Spectroscopic Observation of CAL 83 with XMM-Newton/RGS

We present the first high resolution photospheric X-ray spectrum of a Supersoft X-ray Source, the famous CAL 83 in the Large Magellanic Cloud. The spectrum was obtained with the Reflection Grating Spectrometer on XMM-Newton during the Calibration/Performance Verification phase of the observatory. The spectrum covers the range 20-40 A at an approximately constant resolution of 0.05 A, and shows very significant, intricate detail, that is very sensitive to the physical properties of the object. We present the results of an initial investigation of the spectrum, from which we draw the conclusion that the spectral structure is probably dominated by numerous absorption features due to transitions in the Gshells of the mid-2 elements and the M-shell of Fe, in addition to a few strong K-shell features due to CNO.

Paerels, Frits↗
NASA NTRS2003

Chandra Phase-Resolved X-Ray Spectroscopy of the Crab Pulsar

We present here the first phase-resolved study of the X-ray spectral properties of the Crab Pulsar that covers all pulse phases. The superb angular resolution of the Chandra X-ray Observatory enables distinguishing the pulsar from the surrounding nebulosity, even at pulse minimum. Analysis of the pulse-averaged spectrum measures interstellar photoelectric absorption and scattering by dust grains in the direction of the Crab Nebula. Analysis of the spectrum as a function of pulse phase measures the low-energy X-ray spectral index even at pulse minimum - albeit with large statistical uncertainty. The data are used to set a new upper limit to any thermal component.

Weisskopf, Martin C.↗
NASA NTRS2019

Lynx X-ray Observatory

X-ray observations are indispensable for understanding the cosmos. Their power is immense because much of the baryonic matter and the sites for the most active energy releases in the Universe are primarily observable in X-rays. For the 2030s and beyond, an X-ray observatory with power matching the capabilities in other wavebands is a necessary discovery engine for full exploration of the Universe. JWST and other upcoming major space- and ground-based facilities are expected to greatly expand science frontiers in the coming decades. is presents both a great opportunity and a challenge for a next-generation X-ray observatory. In many areas, such as tracing black holes during the CosmicDawn and understanding the formation and evolution of galaxies, an X-ray observatory is the logical next step. e challenge is that the X-ray science at these new frontiers requires expansion of capabilities by orders of magnitude beyond the current state of the art or anything already planned. Until recently, such gains were not technologically possible. is has changed thanks to recent breakthroughs and sustained maturation of key technologies for X-ray mirrors and detectors. We are reaping the fruits of U.S. investments in these areas over the past 10–15 years. An X-ray observatory that can extend the science frontiers of the post-JWST era is now entirely feasible. Lynx is the mission concept that realizes this vision. It will y revolutionary optics and instrumentation onboard a simple, proven spacecraft. In all aspects, Lynx will be a next-generation Great Observatory that is certain to make a profound impact across the astrophysical landscape. It will provide the depth and breadth to answer the fundamental questions that confront us today; just as importantly, it will have capabilities to address questions we have yet to even ask.

Gaskin, Jessica A.↗
NASA NTRS2019

Arcus: The Soft X-ray Grating Explorer

Arcus provides high-resolution soft X-ray spectroscopy in the 12-50 Å bandpass with unprecedented sensitivity, including spectral resolution > 2500 and effective area > 250 cm2. The three top science goals for Arcus are (1) to measure the effects of structure formation imprinted upon the hot baryons that are predicted to lie in extended halos around galaxies, (2) to trace the propagation of outflowing mass, energy, and momentum from the vicinity of the black hole to extragalactic scales as a measure of their feedback, and (3) to explore how stars form and evolve. Arcus uses the same 12 m focal length grazing-incidence Silicon Pore X-ray Optics (SPOs) that ESA has developed for the Athena mission; the focal length is achieved on orbit via an extendable optical bench. The focused X-rays from these optics are diffracted by high-efficiency Critical-Angle Transmission (CAT) gratings, and the results are imaged with flight-proven CCD detectors and electronics. Combined with the high-heritage NGIS LEOStar-2 spacecraft and launched into 4:1 lunar resonant orbit, Arcus provides high sensitivity and high efficiency observing of a wide range of astrophysical sources.

Randall K Smith↗