2,378 research outputs found
Timing analysis of low-energy gamma ray emission from galactic compact objects using the Gamma Ray Observatory
The principal goal of our phase 1 investigation was the development of techniques and data analysis tools for pulsar searches and timing. After the launch of the Compton Observatory, we received from the Burst and Transient Source Experiment (BATSE) team one day of discriminator large area (DISCLA) data for use in the development and testing of data analysis techniques. Using this first day of data for testing and optimizing our timing tools we detected four x-ray binary pulsars, Vela X-1, Cen X-3, 4U 0115+63, and GX 301-2. Subsequently, we received four more days of data, allowing us to test our timing tools with data from a variety of days. In summary, using the tools we developed based on the first day of data that we received, we have detected 8 pulsars in 5 days of data, or roughly one quarter of the approximately 30 known x-ray binary pulsars. In addition to the pulsars listed above, we detected GX 1+4, 4U 1626-67, OAO 1657-415, and Her X-1. Many of the data analysis tools that we developed have been ported to MSFC and are being used for the analysis of BATSE data. This appendix describes some of the timing tools and presents preliminary pulse period and phase profile results
XSIL: Extensible Scientific Interchange Language
We motivate and define the XSIL language as a flexible, hierarchical, extensible transport language for scientific data objects. The entire object may be represented in the file, or there may be metadata in the XSIL file, with a powerful, fault-tolerant linking mechanism to external data. The language is based on XML, and is designed not only for parsing and processing by machines, but also for presentation to humans through web browsers and web-database technology. There is a natural mapping between the elements of the XSIL language and the object model into which they are translated by the parser. As well as common objects (Parameter, Array, Time, Table), we have extended XSIL to include the IGWDFrame, used by gravitational-wave observatories
Research in cosmic and gamma ray astrophysics
Discussed here is research in cosmic ray and gamma ray astrophysics at the Space Radiation Laboratory (SRL) of the California Institute of Technology. The primary activities discussed involve the development of new instrumentation and techniques for future space flight. In many cases these instrumentation developments were tested in balloon flight instruments designed to conduct new investigations in cosmic ray and gamma ray astrophysics. The results of these investigations are briefly summarized. Specific topics include a quantitative investigation of the solar modulation of cosmic ray protons and helium nuclei, a study of cosmic ray positron and electron spectra in interplanetary and interstellar space, the solar modulation of cosmic rays, an investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances, and a balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon, and nitrogen
A Laboratory Demonstration of High-Resolution Hard X-ray and Gamma-ray Imaging using Fourier-Transform Techniques
A laboratory imaging system has been developed to study the use of Fourier-transform techniques in high-resolution hard x-ray and γ-ray imaging, with particular emphasis on possible applications to high-energy astronomy. We discuss considerations for the design of a Fourier-transform imager and describe the instrumentation used in the laboratory studies. Several analysis methods for image reconstruction are discussed including the CLEAN algorithm and maximum entropy methods. Images obtained using these methods are presented
Pulse Morphology of the Galactic Center Magnetar PSR J1745-2900
We present results from observations of the Galactic Center magnetar, PSR
J1745-2900, at 2.3 and 8.4 GHz with the NASA Deep Space Network 70 m antenna,
DSS-43. We study the magnetar's radio profile shape, flux density, radio
spectrum, and single pulse behavior over a ~1 year period between MJDs 57233
and 57621. In particular, the magnetar exhibits a significantly negative
average spectral index of = -1.86 0.02 when the
8.4 GHz profile is single-peaked, which flattens considerably when the profile
is double-peaked. We have carried out an analysis of single pulses at 8.4 GHz
on MJD 57479 and find that giant pulses and pulses with multiple emission
components are emitted during a significant number of rotations. The resulting
single pulse flux density distribution is incompatible with a log-normal
distribution. The typical pulse width of the components is ~1.8 ms, and the
prevailing delay time between successive components is ~7.7 ms. Many of the
single pulse emission components show significant frequency structure over
bandwidths of ~100 MHz, which we believe is the first observation of such
behavior from a radio magnetar. We report a characteristic single pulse
broadening timescale of = 6.9 0.2 ms at 8.4 GHz.
We find that the pulse broadening is highly variable between emission
components and cannot be explained by a thin scattering screen at distances
1 kpc. We discuss possible intrinsic and extrinsic mechanisms for the
magnetar's emission and compare our results to other magnetars, high magnetic
field pulsars, and fast radio bursts.Comment: 18 pages, 12 figures, Accepted for publication in ApJ on 2018 August
30. v2: Updated to match published versio
The National Virtual Observatory
As a scientific discipline, Astronomy is rather unique. We only have one
laboratory, the Universe, and we cannot, of course, change the initial
conditions and study the resulting effects. On top of this, acquiring
Astronomical data has historically been a very labor-intensive effort. As a
result, data has traditionally been preserved for posterity. With recent
technological advances, however, the rate at which we acquire new data has
grown exponentially, which has generated a Data Tsunami, whose wave train
threatens to overwhelm the field. In this conference proceedings, we present
and define the concept of virtual observatories, which we feel is the only
logical answer to this dilemma.Comment: 5 pages, uses newpasp.sty (included), to appear in "Extragalactic Gas
at Low Redshfit", ASP Conf. Series, J. S. Mulchaey and J. T. Stocke (eds.
Constraints as a destriping tool for Hires images
Images produced from the Maximum Correlation Method sometimes suffer from visible striping artifacts, especially for areas of extended sources. Possible causes are different baseline levels and calibration errors in the detectors. We incorporated these factors into the MCM algorithm, and tested the effects of different constraints on the output image. The result shows significant visual improvement over the standard MCM Method. In some areas the new images show intelligible structures that are otherwise corrupted by striping artifacts, and the removal of these artifacts could enhance performance of object classification algorithms. The constraints were also tested on low surface brightness areas, and were found to be effective in reducing the noise level
A Virtual Data Grid for LIGO
GriPhyN (Grid Physics Network) is a large US collaboration to
build grid services for large physics experiments, one of which is LIGO, a
gravitational-wave observatory. This paper explains the physics and computing
challenges of LIGO, and the tools that GriPhyN will build to address
them. A key component needed to implement the data pipeline is a virtual
data service; a system to dynamically create data products requested during
the various stages. The data could possibly be already processed in a certain
way, it may be in a file on a storage system, it may be cached, or it may need
to be created through computation. The full elaboration of this system will al-low
complex data pipelines to be set up as virtual data objects, with existing
data being transformed in diverse ways
PSR J1024–0719: A Millisecond Pulsar in an Unusual Long-period Orbit
PSR J1024–0719 is a millisecond pulsar that was long thought to be isolated. However, puzzling results concerning its velocity, distance, and low rotational period derivative have led to a reexamination of its properties. We present updated radio timing observations along with new and archival optical data which show that PSR J1024–0719 is most likely in a long-period (2–20 kyr) binary system with a low-mass (≈0.4 M⊙), low-metallicity (z ≈ -0.9 dex) main-sequence star. Such a system can explain most of the anomalous properties of this pulsar. We suggest that this system formed through a dynamical exchange in a globular cluster that ejected it into a halo orbit, which is consistent with the low observed metallicity for the stellar companion. Further astrometric and radio timing observations such as measurement of the third period derivative could strongly constrain the range of orbital parameters
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