32,967 research outputs found
The Angular Momenta of Neutron Stars and Black Holes as a Window on Supernovae
It is now clear that a subset of supernovae display evidence for jets and are
observed as gamma-ray bursts. The angular momentum distribution of massive
stellar endpoints provides a rare means of constraining the nature of the
central engine in core-collapse explosions. Unlike supermassive black holes,
the spin of stellar-mass black holes in X-ray binary systems is little affected
by accretion, and accurately reflects the spin set at birth. A modest number of
stellar-mass black hole angular momenta have now been measured using two
independent X-ray spectroscopic techniques. In contrast, rotation-powered
pulsars spin-down over time, via magnetic braking, but a modest number of natal
spin periods have now been estimated. For both canonical and extreme neutron
star parameters, statistical tests strongly suggest that the angular momentum
distributions of black holes and neutron stars are markedly different. Within
the context of prevalent models for core-collapse supernovae, the angular
momentum distributions are consistent with black holes typically being produced
in GRB-like supernovae with jets, and with neutron stars typically being
produced in supernovae with too little angular momentum to produce jets via
magnetohydrodynamic processes. It is possible that neutron stars are imbued
with high spin initially, and rapidly spun-down shortly after the supernova
event, but the available mechanisms may be inconsistent with some observed
pulsar properties.Comment: ApJ Letters, accepte
Extending Invitations, Becoming Messmates
As music educators we can model proactive advocacy among community members to prevent individuals\u27 reactive violence in response to intolerance for differences. We can offer music-learning tables as safe spaces in which community members openly and collaboratively learn to know each other as individuals with diverse identities and interests. As messmates around the table, we can identify ways that researching, questioning, and being musical together can eradicate fears and the damaging effects of homophobia
An RXTE study of M87 and the core of the Virgo cluster
We present hard X-ray observations of the nearby radio galaxy M87 and the
core of the Virgo cluster using the Rossi X-ray Timing Explorer. These are the
first hard X-ray observations of M87 not affected by contamination from the
nearby Seyfert 2 galaxy NGC4388. Thermal emission from Virgo's intracluster
medium is clearly detected and has a spectrum indicative of kT=2.5keV plasma
with approximately 25% cosmic abundances. No non-thermal (power-law) emission
from M87 is detected in the hard X-ray band, with fluctuations in the Cosmic
X-ray Background being the limiting factor. Combining with ROSAT data, we infer
that the X-ray spectrum of the M87 core and jet must be steep (Gamma_core>1.90$
and Gamma_jet>1.75), and we discuss the implications of this result. In
particular, these results are consistent with M87 being a mis-aligned BL-Lac
object.Comment: 8 pages, 2 postscript figures. Accepted for publication in Ap
Apollo telescope mount: A partial listing of scientific publications, supplement 2
Reports are compilations of bibliographies from the principal investigator groups of the Apollo Telescope Mount (Skylab solar observatory facility) that gathered data from May 28, 1973, to February 8, 1974. The analysis of these data is presently under way and is expected to continue for several years. The publications listed in this report are divided into the following categories: (1) Journal Publications, (2) Journal Publications Submitted, (3) Other Publications, (4) Presentations--National and International Meetings, and (5) Other Presentations. An author index is included together with errata for the first report
Apollo telescope mount: A partial listing of scientific publications and presentations
A compilation of bibliographies from the principal investigator groups of the Apollo Telescope Mount (Skylab solar observatory facility) which gathered data from May 28, 1973, to February 8, 1974 is presented. The analysis of these data is presently under way and is expected to continue for several years. The publications listed are divided into the following categories: (1) Journal Publications, (2) Journal Publications Submitted, (3) Other Publications, (4) Presentations - National International Meetings, and (5) Other Presentations. An author index is also included
Apollo telescope mount. A partial listing of scientific publications and presentations, supplement 1
Compilations of bibliographies from the principal investigator groups of the Apollo Telescope Mount (Skylab solar observatory facility) are presented. The publications listed are divided into the following categories: (1) journal publications, (2) journal publications submitted, (3) other publications, (4) presentations - national and international meetings; and (5) other presentations
Automated reduction of instantaneous flow field images
An automated data reduction system for the analysis of interference fringe patterns obtained using the particle image velocimetry technique is described. This system is based on digital image processing techniques that have provided the flexibility and speed needed to obtain more complete automation of the data reduction process. As approached here, this process includes scanning/searching for data on the photographic record, recognition of fringe patterns of sufficient quality, and, finally, analysis of these fringes to determine a local measure of the velocity magnitude and direction. The fringe analysis as well as the fringe image recognition are based on full frame autocorrelation techniques using parallel processing capabilities
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