Rotation and Accretion Powered Pulsars

Abstract

Pulsar astrophysics has come a long way in the 40 years since thediscovery of the first pulsar by Bell and Hewish. From humblebeginnings as bits of 'scruff' on the Cambridge University group'schart recorder paper, the field of pulsars has blossomed into a majorarea of mainstream astrophysics, with an unparalleled diversity ofastrophysical applications. These range from Nobel-celebrated testingof general relativity in the strong-field regime to constraining theequation-of-state of ultradense matter; from probing the winds of massivestars to globular cluster evolution.Previous notable books on the subject of pulsars have tended to focus on someparticular topic in the field. The classic text Pulsars by Manchesterand Taylor (1977 San Francisco, CA: Freeman) targeted almost exclusively rotation-powered radio pulsars,while the Mészáros book High-Energy Radiation from Magnetized NeutronStars (1992 Chicago, IL: University of Chicago Press) considered both rotation- and accretion-powered neutron stars, but focused on their radiation at x-ray energies and above. The recentbook Neutron Stars 1 by Haensel et al (2007 Berlin: Springer) considers only the equation ofstate and neutron-star structure.Into this context appears Rotation and Accretion Powered Pulsars,by Pranab Ghosh. In contrast to other books, here the author takesan encyclopedic approach and attempts to synthesize practically all ofthe major aspects of the two main types of neutron star. This is ambitious.The only comparable undertaking is the useful but more elementaryLyne and Graham-Smith text Pulsar Astronomy (1998 Cambridge: Cambridge University Press), or CompactStellar X-ray Sources (eds Lewin and van der Klis, 2006 Cambridge: Cambridge University Press), an anthology of technical review articles that also includes black hole topics.Rotation and Accretion Powered Pulsars thus fills a clear void in thefield, providing a readable, graduate-level book that covers nearly everythingyou ever wanted to know about pulsars but were afraid to ask.Chapter 1 begins a brief and interesting account of the discoveryof pulsars, followed by an overview of the rotation-poweredand accretion-powered populations. The following four chapters arefairly detailed and reasonably quantitative descriptions of neutronstar interiors. This is no easy feat, given that a descriptionof the physics of neutron stars demands a deep understanding of allmajor physical forces, and must include general relativity as well asdetailed particle physics. The historical notes at the beginning ofChapter 2 are particularly fascinating, recounting the path to today'sunderstanding of neutron stars in very interesting detail. Chapter 7presents rotation-powered pulsar radio properties, and a nice descriptionof pulsar timing, including relativistic and non-relativistic binaries andGR tests. The remaining chapters tackle a variety of topics includingbinary evolution, superfluidity, accretion-powered pulsar properties,magnetospheres and emission mechanisms, magnetic fields, spin evolutionand strange stars. The coverage is somewhat uneven, with the strangestar chapter, for example, an obvious afterthought.The utility of an encyclopedia lies in its breadth and in how up-to-dateit is. Although admirable in its intentions, the Ghosh book does omitsome major pulsar topics. This book leaves the impression thatrotation-powered pulsars produce only radio emission; hardly (if at all)mentioned is the vast literature on their infrared, optical, and evenmore importantly, x-ray and gamma-ray emission, the latter being farmore relevant to the pulsar 'machine' than the energetically puny radio output.Also absent are pulsar winds; this is particularly puzzling given boththe lovely wind nebula that graces the book's cover, and the centralrole the wind plays as primary sink of the rotation power. One of the most actively pursued topics in pulsar astrophysics in thepast decade, magnetars, receives only a passing mention, thoughadmittedly, they are neither rotation- nor accretion-powered.Also, some sections are slightly out of date: the fastest known pulsar has frequency 716 Hz, not 642 Hz; there are more braking indexes measured as well as a second braking index; nulling has been tied to spin-down.Still, this book stands alone in its bold attempt at a unifying, advancedpicture of the two main areas of neutron-star science: rotation andaccretion powered pulsars. It is thus a valuable and unique asset for anyoneinterested in the topic; I am delighted to own a copy. I personally very much hope author Ghosh will consider filling in some of the gaps in his book in a second edition, as his text is accessible and a pleasure toread, and his vision and ambition are admirable.