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 $\langle\alpha\rangle$ = -1.86 $\pm$ 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 $\langle\tau_{d}\rangle$ = 6.9 $\pm$ 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 $\gtrsim$ 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

A novel method for transient detection in high-cadence optical surveys: Its application for a systematic search for novae in M31

[abridged] In large-scale time-domain surveys, the processing of data, from procurement up to the detection of sources, is generally automated. One of the main challenges is contamination by artifacts, especially in regions of strong unresolved emission. We present a novel method for identifying candidates for variables and transients from the outputs of such surveys' data pipelines. We use the method to systematically search for novae in iPTF observations of the bulge of M31. We demonstrate that most artifacts produced by the iPTF pipeline form a locally uniform background of false detections approximately obeying Poissonian statistics, whereas genuine variables and transients as well as artifacts associated with bright stars result in clusters of detections, whose spread is determined by the source localization accuracy. This makes the problem analogous to source detection on images produced by X-ray telescopes, enabling one to utilize tools developed in X-ray astronomy. In particular, we use a wavelet-based source detection algorithm from the Chandra data analysis package CIAO. Starting from ~2.5x10^5 raw detections made by the iPTF data pipeline, we obtain ~4000 unique source candidates. Cross-matching these candidates with the source-catalog of a deep reference image, we find counterparts for ~90% of them. These are either artifacts due to imperfect PSF matching or genuine variable sources. The remaining ~400 detections are transient sources. We identify novae among these candidates by applying selection cuts based on the expected properties of nova lightcurves. Thus, we recovered all 12 known novae registered during the time span of the survey and discovered three nova candidates. Our method is generic and can be applied for mining any target out of the artifacts in optical time-domain data. As it is fully automated, its incompleteness can be accurately computed and corrected for.Comment: 16 pages, 8 figures, accepted to A&

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.

VLA Observations of Candidate Supernova Remnants from the Clark Lake 30.9 MHz Galactic Plane Survey

We report the results of 1464 MHz continuum VLA observations of eight fields containing unidentified small-diameter objects associated with candidate supernova remnants from the Clark Lake 30.9 MHz galactic plane survey. The observations were made in the C configuration, giving a resolution of -12-20 arcsec, and a sensitivity of typically <0.5 mJy per beam. Polarization measurements were made as well. One of the 30.9 MHz candidates, G41.4+ 1.2, appears to be confirmed as a supernova remnant by our observations. Of the remaining seven fields observed, three were found to contain small-diameter objects which met some of the criteria for nonthermal origin, but will require further study to evaluate whether they are associated with the candidate supernova remnants. Two of the fields were found to contain groups of unresolved objects consistent with expectations for extragalactic background sources. In these cases the 30.9 MHz observations, which could not resolve the individual sources but would view them as a single extended source, may have mistakenly identified them as possible supernova remnants. Finally, two fields contained bright H II region

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