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Author: Timothy Eugene Edward Olszanski
Publisher:
ISBN:
Category : Neutron stars
Languages : en
Pages : 232
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Book Description
Compact Objects (Neutron Stars) form in the last moments of a star's life, during the violent events known as supernovae. As the star's core fusion falters, matter undergoes a dramatic gravitational compression resulting in internal densities rivaling subatomic particles. Ever since their discovery in the mid-twentieth century, these highly magnetized and rapidly rotating balls of condensed matter have provided a bountiful playground for astronomers seeking out exotic physics. Neutron Stars that emit electromagnetic radiation are seen by observers as Pulsars, named such for the pulse of intensity as the pulsar's radiation beam passes into our line of sight. These beams are comprised of two unique regions with differing phenomenology; core emission that arises close to the pulsar polar cap and centered within the radiation beam, and higher altitude conal emission that lies along the beam's periphery. While pulsars can and do emit over a wide frequency range, most known pulsars are seen as radio sources, at sensitivities where studies of the pulsar single-pulses allows us to probe the rich details of the plasma-filled pulsar magnetosphere. Even then, the radio emission often has a steep spectra, restricting the frequencies in which radio telescopes can study pulsars. We have utilized the unmatched sensitivity of Arecibo Observatory to conduct a multi-frequency single-pulse survey, between 327 MHz and the novel 4.5 GHz, of Arecibo's brightest high-frequency pulsars. The broad frequency range and single-pulse resolutions have allowed us to set accurate beam classifications for these nearly two dozen pulsars while extending constraints on important population trends to higher frequencies. Several of the pulsars in our survey exhibit deviant behavior, and are thus useful as followup case studies to further our understanding of pulsar radio emission. One of the most interesting cases involves pulsar B0823+26, where we find evidence for an age-dependent death-line separating core and conal dominated pulsars, suggesting that the plasma generating capabilities of a pulsar changes as they age. For the other three, they fall in the "Partial Cone"' class; a type of pulsar that is characterized by strong delays in their emission. We find that all three of these pulsars show evidence of core emission.
Author: Timothy Eugene Edward Olszanski
Publisher:
ISBN:
Category : Neutron stars
Languages : en
Pages : 232
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Book Description
Compact Objects (Neutron Stars) form in the last moments of a star's life, during the violent events known as supernovae. As the star's core fusion falters, matter undergoes a dramatic gravitational compression resulting in internal densities rivaling subatomic particles. Ever since their discovery in the mid-twentieth century, these highly magnetized and rapidly rotating balls of condensed matter have provided a bountiful playground for astronomers seeking out exotic physics. Neutron Stars that emit electromagnetic radiation are seen by observers as Pulsars, named such for the pulse of intensity as the pulsar's radiation beam passes into our line of sight. These beams are comprised of two unique regions with differing phenomenology; core emission that arises close to the pulsar polar cap and centered within the radiation beam, and higher altitude conal emission that lies along the beam's periphery. While pulsars can and do emit over a wide frequency range, most known pulsars are seen as radio sources, at sensitivities where studies of the pulsar single-pulses allows us to probe the rich details of the plasma-filled pulsar magnetosphere. Even then, the radio emission often has a steep spectra, restricting the frequencies in which radio telescopes can study pulsars. We have utilized the unmatched sensitivity of Arecibo Observatory to conduct a multi-frequency single-pulse survey, between 327 MHz and the novel 4.5 GHz, of Arecibo's brightest high-frequency pulsars. The broad frequency range and single-pulse resolutions have allowed us to set accurate beam classifications for these nearly two dozen pulsars while extending constraints on important population trends to higher frequencies. Several of the pulsars in our survey exhibit deviant behavior, and are thus useful as followup case studies to further our understanding of pulsar radio emission. One of the most interesting cases involves pulsar B0823+26, where we find evidence for an age-dependent death-line separating core and conal dominated pulsars, suggesting that the plasma generating capabilities of a pulsar changes as they age. For the other three, they fall in the "Partial Cone"' class; a type of pulsar that is characterized by strong delays in their emission. We find that all three of these pulsars show evidence of core emission.
Author: Emilie Parent
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"Pulsars are fascinating objects that have taught us much about our Universe, from gravitational radiation to the extreme states of matter and planets beyond our solar system. Most pulsars are detected via the beams of radio waves they radiate from their magnetic poles. Conducting high-time-resolution surveys with powerful radio telescopes to discover more pulsars has been a gateway to new science. A notable example is the discovery of fast radio bursts (FRBs): short-duration and extremely energetic extragalactic radio transients of unknown origin. In this thesis, we report on results of two large-scale surveys for radio pulsars and fast transients. The first is the 1.4-GHz PALFA survey, conducted with the 305-m Arecibo radio telescope in Puerto Rico from 2004 until the collapse of the instrument in 2020. PALFA targeted the Galactic plane, where the neutron star density is greatest, with the goal of probing a distant population located deep in the plane. Chapters 3 and 4 present the discovery and study of 80 pulsars discovered by PALFA, more than a third of the total survey yield. Spin and astrometric measurements were obtained through long-term pulsar timing observations carried out at various facilities, allowing us to determine the pulsars' properties. More specifically, Chapter 3 focuses on the timing analysis of eight PALFA-discovered binary millisecond pulsars (MSPs): a class of old and fast-spinning (period
Author: Scott Campbell Lundgren
Publisher:
ISBN:
Category : Pulsars
Languages : en
Pages : 262
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Author: Chitrang Patel
Publisher:
ISBN:
Category :
Languages : en
Pages :
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"PALFA (Pulsar Arecibo L-band Feed Array) is an on-going survey of the Galactic plane at 1.4 GHz, searching for radio pulsars (rapidly rotating highly magnetized neutron stars) with the Arecibo 305-m single dish radio telescope located in Puerto Rico. Begun in 2004, PALFA has discovered 163 radio pulsars including 13 RRATs (Rotating RAdio Transients -- a recently discovered class of pulsars with sporadic emission) and 1 FRB (Fast Radio Bursts -- a mysterious new class of milliseconds duration bright radio bursts). We have written and implemented a new data analysis pipeline to improve the search for long period pulsars (spin period P > 0.1 s), RRATs and FRBs. The new pipeline is an improvement to the original data analysis pipeline with a more systematic processing and post-processing approach to identify astrophysical individually detectable single pulses in the time domain. The original pipeline consisted of a matched-filtering search technique as a part of the single pulse analysis of the pipeline. To do a more rigorous search, we appended the pipeline with a grouping algorithm which gathers similar single pulse events into a single group based on proximity in time and DM (dispersion measure -- the integrated column density of free electrons along a particular line of sight). Each group is ranked based on the criteria that astrophysical pulses follow (their signal-to-noise peaks at the optimal DM and falls off on either sides). A final candidate diagnostic plot is produced for each potential astrophysical candidate as identified by the grouping algorithm. Each candidate is then subject to a series of heuristic ratings followed by evaluation by a machine-learning algorithm. The final candidate diagnostic plots are uploaded to an online candidate viewer for by-eye inspection by the members of the PALFA consortium. Using this new pipeline we have discovered 5 new pulsars and 2 RRATs, 3 of which were detected uniquely by the single pulse analysis of the pipeline and 4 were detected by both single pulse and periodicity analysis. The discovered pulsars are now being regularly monitored as a part of our timing campaign. We plan to reprocess all PALFA archival data in Summer 2016 using this newly developed single-pulse pipeline. In doing so, we expect to find at least 9 new pulsars (including RRATs and FRBs) that could have been missed by the original pipeline." --
Author: Andrew Lyne
Publisher: Cambridge University Press
ISBN: 1108864104
Category : Science
Languages : en
Pages : 422
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Book Description
After more than half a century since their unexpected discovery and identification as neutron stars, the observation and understanding of pulsars touches upon many areas of astronomy and astrophysics. The literature on pulsars is vast and the observational techniques used now cover the whole of the electromagnetic spectrum from radio to gamma-rays. Now in its fifth edition, this volume has been reorganised and features new material throughout. It provides an introduction in historical and physical terms to the many aspects of neutron stars, including condensed matter, physics of the magnetosphere, supernovae and the development of the pulsar population, propagation in the interstellar medium, binary stars, gravitation and general relativity. The current development of a new generation of powerful radio telescopes, designed with pulsar research in mind, makes this survey and guide essential reading for a growing body of students and astronomers.
Author: Bryan Anthony Jacoby
Publisher: Universal-Publishers
ISBN: 1581123930
Category : Science
Languages : en
Pages : 116
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Book Description
We present the results of a large-area survey for millisecond pulsars (MSPs) at moderately high galactic latitudes with the 64 m Parkes radio telescope, along with follow-up timing and optical studies of the newly-discovered pulsars and several others. Major results include the first precise measurement of the mass of a fully recycled pulsar and measurement of orbital period decay in a double neutron star binary system allowing a test of general relativity along with improved measurements of the neutron star masses. In a survey of approx. 4,150 square degrees, we discovered 26 previously unknown pulsars, including 7 "recycled" millisecond or binary pulsars. Several of these recycled pulsars are particularly interesting: PSR J1528-3146 is in a circular orbit with a companion of at least 0.94 solar masses; it is a member of the recently recognized class of intermediate mass binary pulsar (IMBP) systems with massive white dwarf companions. We have detected optical counterparts for this and one other IMBP system; taken together with optical detections and non-detections of several similar systems, our results indicate that the characteristic age consistently overestimates the time since the end of mass accretion in these recycled systems. This result implies that the pulsar spin period at the end of the accretion phase is not dramatically shorter than the observed period as is generally assumed. PSR J1600-3053 is among the best high-precision timing pulsars known and should be very useful as part of an ensemble of pulsars used to detect very low frequency gravitational waves. PSR J1738+0333 has an optical counterpart which, although not yet well-studied, has already allowed a preliminary measurement of the system's mass ratio. The most significant discovery of this survey is PSR J1909-3744, a 2.95 ms pulsar in an extremely circular 1.5 d orbit with a low-mass white dwarf companion. Though this system is a fairly typical low-mass binary pulsar (LMBP) system, it has several exceptional qualities: an extremely narrow pulse profile and stable rotation have enabled the most precise long-term timing ever reported, and a nearly edge-on orbit gives rise to a strong Shapiro delay signature in the pulse timing data which has allowed the most precise measurement of the mass of a millisecond pulsar: 1.438 ± 0.024 solar masses. Our accurate parallax distance measurement, d = 1.14 +0.08 / -0.07 kpc, combined with the mass of the optically-detected companion, 0.2038 ± 0.022 solar masses, will provide an important calibration for white dwarf models relevant to other LMBP companions. We have measured the decay of the binary period of the double neutron star system B2127+11C in the globular cluster M15. This has allowed an improved measurement of the mass of the pulsar, 1.3584 ± 0.0097 solar masses, and companion, 1.3544 ± 0.0097 solar masses, as well as a test of general relativity at the 3% level. We find that the proper motions of this pulsar as well as B2127+11A and B2127+11B are consistent with each other and with one published measurement of the cluster proper motion. We have discovered three binary millisecond pulsars in the globular cluster M62 using the 100-m Green Bank Telescope (GBT). These pulsars are the first objects discovered with the GBT. We briefly describe a wide-bandwidth coherent dedispersion backend used for some of the high precision pulsar timing observations presented here.
Author: D. R. Lorimer
Publisher: Cambridge University Press
ISBN: 9780521828239
Category : Science
Languages : en
Pages : 316
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Book Description
This 2004 book provides a concise description of pulsar research, presenting key techniques, background information and results.
Author: John Antoniadis
Publisher: Springer
ISBN: 3319098977
Category : Science
Languages : en
Pages : 99
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Book Description
The focus of his prize-winning thesis is on observations and modeling of binary millisecond pulsars. But in addition, John Antoniadis covers a wide range of observational measurements of binary compact stars systems and tests of General Relativity, like indirect measurements of gravitational wave emission and posing the most stringent constraints on Scalar-Tensor gravity theories. Among others, he presents a system that hosts the most massive neutron star known to date, which has important ramifications for strong-field gravity and nuclear physics. This impressive work was awarded the Otto-Hahn Medal of the Max-Planck Society and the Best PhD in Gravity, Particle and Atomic physics award by the German Physics Society (DPG).
Author: Geoff McNamara
Publisher: Springer Science & Business Media
ISBN: 038776562X
Category : Science
Languages : en
Pages : 192
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Book Description
Pulsars are rapidly spinning neutron stars, the collapsed cores of once massive stars that ended their lives as supernova explosions. In this book, Geoff McNamara explores the history, subsequent discovery and contemporary research into pulsar astronomy. The story of pulsars is brought right up to date with the announcement in 2006 of a new breed of pulsar, Rotating Radio Transients (RRATs), which emit short bursts of radio signals separated by long pauses. These may outnumber conventional radio pulsars by a ratio of four to one. Geoff McNamara ends by pointing out that, despite the enormous success of pulsar research in the second half of the twentieth century, the real discoveries are yet to be made including, perhaps, the detection of the hypothetical pulsar black hole binary system by the proposed Square Kilometre Array - the largest single radio telescope in the world.
Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 1288
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