Multifrequency Search & Classification of the Transient Radio Sky PDF Download
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Author: Adam James Stewart
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Adam James Stewart
Publisher:
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Category :
Languages : en
Pages :
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Author: Evan Francis Keane
Publisher: Springer Science & Business Media
ISBN: 3642196276
Category : Science
Languages : en
Pages : 195
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The high time-resolution radio sky represents unexplored astronomical territory. This thesis presents a study of the transient radio sky, focussing on millisecond scales. As such, the work is concerned primarily with neutron stars. In particular this research concentrates on a recently identified group of neutron stars, known as RRATs, which exhibit radio bursts every few minutes to every few hours. After analysing neutron star birthrates, a re-analysis of the Parkes Multibeam Pulsar Survey is described which has resulted in the discovery of 19 new transient radio sources. Of these, 12 have been seen to repeat and a follow-up campaign of observations has been undertaken. These studies have greatly increased our knowledge of the rotational properties of RRATs and enable us to conclude that they are pulsars with extreme nulling and/or pulse-to-pulse modulation. Although the evolution of neutron stars post-supernova is not yet understood, it seems that RRATs fit into the emerging picture in which pulsar magnetospheres switch between stable configurations.
Author: Alexander Josephy
Publisher:
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Category :
Languages : en
Pages :
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"Fast Radio Bursts (FRBs) are micro-to-millisecond duration transients of extragalactic origin. Despite FRB rate estimates of thousands per sky per day, only 30 sources have been detected in the now decade since the initial discovery, and the progenitor of FRBs remains a mystery. This will soon change, as a dedicated 24/7 real-time search, expected to detect tens of FRBs every day, is in the early stages of commissioning. The search is hosted by a novel software-driven telescope with a ~250 square degree field of view and a collecting area of ~8000 square metres. The telescope is located at the Dominion Astrophysical Observatory (DRAO), and was designed for the Canadian Hydrogen Intensity Mapping Experiment (CHIME). This thesis follows the development of components in the later stages of the CHIME/FRB pipeline, where the focus shifts from detection to classification. These developments include: algorithms to group detections over multi-dimensional search spaces and uniquely identify single-pulses; an algorithm to sift candidate events resembling radio-frequency interference (RFI), with preparations for the application of machine learning classifiers; a method for localizing bright bursts, exchanging memory and precomputation for sub-millisecond execution time; and an architecture for the event-based pipeline, designed to scale to an arbitrary number of CPU cores and machines. Finally, a stress test of the event-based pipeline was performed, using simulated events based on the known pulsar population. The pipeline comfortably handles 300,000 fake events spanning 24 hours of fake observation, reaffirming that the FRB search will not suffer the pulsar foreground." --
Author: Kunal P. Mooley
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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While synoptic surveys in the optical and at high energies have revealed a rich discovery phase space of slow transients, a similar yield is still awaited in the radio. Majority of the past blind surveys, carried out with radio interferometers, have suffered from a low yield of slow transients, ambiguous transient classifications, and contamination by false positives. The newly-refurbished Karl G. Jansky Array (Jansky VLA) offers wider bandwidths for accurate RFI excision as well as substantially-improved sensitivity and survey speed compared with the old VLA. The Jansky VLA thus eliminates the pitfalls of interferometric transient search by facilitating sensitive, wide-field, and near-real-time radio surveys and enabling a systematic exploration of the dynamic radio sky. This thesis aims at carrying out blind Jansky VLA surveys for characterizing the radio variable and transient sources at frequencies of a few GHz and on timescales between days and years. Through joint radio and optical surveys, the thesis addresses outstanding questions pertaining to the rates of slow radio transients (e.g. radio supernovae, tidal disruption events, binary neutron star mergers, stellar flares, etc.), the false-positive foreground relevant for the radio and optical counterpart searches of gravitational wave sources, and the beaming factor of gamma-ray bursts. The need for rapid processing of the Jansky VLA data and near-real-time radio transient search has enabled the development of state-of-the-art software infrastructure. This thesis has successfully demonstrated the Jansky VLA as a powerful transient search instrument, and it serves as a pathfinder for the transient surveys planned for the SKA-mid pathfinder facilities, viz. ASKAP, MeerKAT, and WSRT/Apertif.
Author: Kunal Mooley
Publisher:
ISBN: 9781516989874
Category :
Languages : en
Pages : 304
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Book Description
Most of what is currently known about slow radio transients (supernovae, gamma-ray bursts, tidal disruption events, stellar flares, etc.) has come via radio follow-up of objects identified by synoptic survey telescopes at optical, X-ray or gamma-ray wavelengths. However, with the ability to capture obscured, unbeamed and magnetically-driven phenomena, radio surveys offer an opportunity to find unique cosmic transients and study their diagnostic features. This thesis describes the first systematic exploration of the dynamic radio sky on timescales between one day to several years using multi-epoch widefield surveys with the Karl G. Jansky Array (Jansky VLA). It announces the discovery of several fascinating transients that appear to be unique to the radio, and thus establishes the Jansky VLA as an efficient transient discovery machine. This thesis has enormous implications for designing efficient transient surveys during the era of the Square Kilometer Array (SKA), the demographics of variable radio sources including AGN, future searches of the radio counterparts of gravitational-wave sources, and the search for new classes of radio transients.
Author: Kunal P. Mooley
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 564
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Book Description
While synoptic surveys in the optical and at high energies have revealed a rich discovery phase space of slow transients, a similar yield is still awaited in the radio. Majority of the past blind surveys, carried out with radio interferometers, have suffered from a low yield of slow transients, ambiguous transient classifications, and contamination by false positives. The newly-refurbished Karl G. Jansky Array (Jansky VLA) offers wider bandwidths for accurate RFI excision as well as substantially-improved sensitivity and survey speed compared with the old VLA. The Jansky VLA thus eliminates the pitfalls of interferometric transient search by facilitating sensitive, wide-field, and near-real-time radio surveys and enabling a systematic exploration of the dynamic radio sky. This thesis aims at carrying out blind Jansky VLA surveys for characterizing the radio variable and transient sources at frequencies of a few GHz and on timescales between days and years. Through joint radio and optical surveys, the thesis addresses outstanding questions pertaining to the rates of slow radio transients (e.g. radio supernovae, tidal disruption events, binary neutron star mergers, stellar flares, etc.), the false-positive foreground relevant for the radio and optical counterpart searches of gravitational wave sources, and the beaming factor of gamma-ray bursts. The need for rapid processing of the Jansky VLA data and near-real-time radio transient search has enabled the development of state-of-the-art software infrastructure. This thesis has successfully demonstrated the Jansky VLA as a powerful transient search instrument, and it serves as a pathfinder for the transient surveys planned for the SKA-mid pathfinder facilities, viz. ASKAP, MeerKAT, and WSRT/Apertif.
Author: Martin Ellis Bell
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Małgorzata Piętka
Publisher:
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Category :
Languages : en
Pages :
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Category :
Languages : en
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Author: A. Richard Thompson
Publisher: Wiley-Interscience
ISBN:
Category : Nature
Languages : en
Pages : 568
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Book Description
A unified description of the theory and practice of radio interferometry and synthesis mapping techniques as they apply to astronomy and geology. Beginning with an historical review, it goes on to provide a detailed description of all aspects of radio inferometry, from basic principles through instrumental design to data reduction. Over 450 original papers and monographs are cited.
