August 14, 2009 Journal article Open Access

Detection of High-Energy Gamma-Ray Emission from the Globular Cluster 47 Tucanae with Fermi

Gudlaugur Johannesson; Dario Gasparrini; A. Y. Rodriguez; J. B. Thayer; Randall P. Johnson; L. Tibaldo; L. Tibaldo; J. F. Ormes; R. Dubois; P. Wang; M. Pepe; M. Pepe; Ronaldo Bellazzini; V. Vasileiou; V. Vasileiou; Markus Ackermann; M. E. Monzani; R. E. Hughes; Yasushi Fukazawa; Felix Ryde; Felix Ryde; A. Chekhtman; A. Chekhtman; N.A. Webb; Stefano Ciprini; Stefano Ciprini; W. McConville; W. McConville; Pascal Bruel; Francesco Giordano; Francesco Giordano; Roger W. Romani; Jürgen Knödlseder; B. Giebels; I. A. Grenier; E. Hays; W. B. Atwood; F. de Palma; F. de Palma; T. A. Porter; Persis S. Drell; Tyrel J. Johnson; Tyrel J. Johnson; T. Reposeur; A. A. Moiseev; A. A. Moiseev; M. Kuss; P. D. Smith; Eric Charles; F. Gargano; B. Lott; A. W. Borgland; S. Ritz; G. Godfrey; Olaf Reimer; Charles D. Dermer; Yasunobu Uchiyama; Seth Digel; Roger Blandford; Luca Latronico; D. J. Thompson; Jean Ballet; E. Nuss; W. B. Focke; J. P. Norris; A. Morselli; M. Dormody; S. Murgia; F. Kuehn; V. Vitale; V. Vitale; T. Kamae; Carmelo Sgrò; Riccardo Rando; Riccardo Rando; B. Berenji; J. H. Panetta; N. Kawai; Igor V. Moskalenko; Elliott D. Bloom; M. Frailis; D. J. Suson; L. S. Rochester; Hiroyasu Tajima; D. Horan; M. Pierbattista; Jean-Luc Starck; Y. Hanabata; Morihiro Hayashida; S. J. Fegan; Gloria Spandre; F. Piron; C. Monte; C. Monte; Hiromitsu Takahashi; Nicola Omodei; P. Spinelli; P. Spinelli; D. Dumora; Hartmut Sadrozinski; A. A. Abdo; Jan Conrad; Jan Conrad; Neil Gehrels; Neil Gehrels; Claudia Cecchi; Claudia Cecchi; G. A. Caliandro; G. A. Caliandro; T. Ohsugi; Sylvain Chaty; M. N. Mazziotta; A. Sander; Luca Baldini; F. Loparco; F. Loparco; Brian L Winer; Johann Cohen-Tanugi; W. Mitthumsiri; M. Roth; P. Fusco; P. Fusco; C. Meurer; T. H. Burnett; E. Do Couto E Silva; Tsunefumi Mizuno; Denis Bastieri; Denis Bastieri; B. M. Baughman; J. G. Thayer; Alessandro Brez; Matthew Kerr; Kent S. Wood; W. N. Johnson; T. Ylinen; T. Ylinen; J. Bregeon; Emanuele Bonamente; Emanuele Bonamente; Peter F. Michelson; T. L. Usher; Marco Ajello; C. Favuzzi; C. Favuzzi; S. Rainò; S. Rainò; Nicola Giglietto; Nicola Giglietto; Guido Barbiellini; Guido Barbiellini; Magnus Axelsson; M. N. Lovellette; Julie McEnery; V. Pelassa; S. Cutini; A. Reimer; David Sánchez; P. M. Saz Parkinson; J. Lande; Sylvain Guiriec; Hideaki Katagiri; Ö. Çelik; Gino Tosti; Gino Tosti; C. Farnier; M. Brigida; M. Brigida; M. Ziegler; P. A. Caraveo; M. Razzano; A. Makeev; A. Makeev; Diego F. Torres; Diego F. Torres; David Smith; E. Orlando; M. S. Strickman; Francesco Longo; Francesco Longo; S. Germani; S. Germani; James Chiang; J. M. Casandjian; N. Vilchez; T. Glanzman; R. A. Cameron; Nanda Rea; D. Parent; M. Lemoine-Goumard; Takaaki Tanaka; R. Claus; J. E. Grove; L. Guillemot; A. Tramacere; A. S. Johnson; P. L. Nolan; C. C. Cheung; P. Lubrano; P. Lubrano; Alice K. Harding

Gamma-Ray Pulsar Bonanza Most of the pulsars we know about were detected through their radio emission; a few are known to pulse gamma rays but were first detected at other wavelengths (see the Perspective by Halpern ). Using the Fermi Gamma-Ray Space Telescope, Abdo et al. (p. 840 , published online 2 July; see the cover) report the detection of 16 previously unknown pulsars based on their gamma-ray emission alone. Thirteen of these coincide with previously unidentified gamma-ray sources, solving the 30-year-old mystery of their identities. Pulsars are fast-rotating neutron stars. With time they slow down and cease to radiate; however, if they are in a binary system, they can have their spin rates increased by mass transfer from their companion stars, starting a new life as millisecond pulsars. In another study, Abdo et al. (p. 845 ) report the detection of gamma-ray emission from the globular cluster 47 Tucanae, which is coming from an ensemble of millisecond pulsars in the cluster's core. The data imply that there are up to 60 millisecond pulsars in 47 Tucanae, twice as many as predicted by radio observations. In a further companion study, Abdo et al. (p. 848 , published online 2 July) searched Fermi Large Area Telescope data for pulsations from all known millisecond pulsars outside of stellar clusters, finding gamma-ray pulsations for eight of them. Their properties resemble those of other gamma-ray pulsars, suggesting that they share the same basic emission mechanism. Indeed, both sets of pulsars favor emission models in which the gamma rays are produced in the outer magnetosphere of the neutron star.