A Study Of Recycled Pulsars In Globular Clusters

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.

Proceedings of the NATO Advanced Research Workshop on X-Ray Binaries and the Formation of Binary and Millisecond Radio Pulsars, Santa Barbara, CA, U.S.A., Januari 21-25, 1991

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The discovery 25 years ago of the remarkable astronomical objects known as pulsars--and their identification as neutron stars--fulfilled a prediction made more than 30 years earlier. Over 550 pulsars are now known, almost all detected at radio frequencies which capture their distinctive bursts of electromagnetic energy. These pulse periods range from 1.5 milliseconds to several seconds. Most pulsars are single neutron stars but they can also exist in a binary orbit with a companion. Observations have revealed a wealth of detail about the structure and evolution of pulsars and the pulse-emission process, giving new insight into the behavior of matter in the presence of extreme gravitational and electromagnetic fields. In fact, pulsars have unique physical properties which make them nearly ideal as probes for a wide range of physical studies. This volume gathers together up-to-date findings in this area, representing a valuable resource for theoretical and particle physicists as well astrophysicists and astronomers. The contributors are recognized experts in the field, and include such well-known authorities as Joe Taylor who describes his Nobel-Prize winning work (Physics 1993).

One of the most attractive features of the young discipline of Space Science is that many of the original pioneers and key players involved are still available to describe their field. Hence, at this point in history we are in a unique position to gain first-hand insight into the field and its development. To this end, The Century of Space Science, a scholarly, authoritative, reference book presents a chapter-by-chapter retrospective of space science as studied in the 20th century. The level is academic and focuses on key discoveries, how these were arrived at, their scientific consequences and how these discoveries advanced the thoughts of the key players involved. With over 90 world-class contributors, such as James Van Allen, Cornelis de Jager, Eugene Parker, Reimar Lüst, and Ernst Stuhlinger, and with a Foreword by Lodewijk Woltjer (past ESO Director General), this book will be immensely useful to readers in the fields of space science, astronomy, and the history of science. Both academic institutions and researchers will find that this major reference work makes an invaluable addition to their collection.

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.

The papers in this volume present a recent survey of important results in the field of supernovae and pulsars. The review articles are likely to prove valuable because of their pedagogical nature to students and other entrants in the field. For researchers already working in this field, observational results and the details of theoretical investigations presented systematically are likely to stimulate further debates regarding classification of supernovae types Ia Ib and II and their progenitors and their relationship. New results are presented.