International Conference: ISOLATED NEUTRON STARS: FROM THE INTERIOR TO THE SURFACE April, 24-28, 2006 London, UK ------------------------------------------------ First Announcement - Invitation ------------------------------------------------ Dear Colleague, we are pleased to invite you to a conference entitled ISOLATED NEUTRON STARS: FROM THE INTERIOR TO THE SURFACE to be held in London, UK, April 24-28, 2006. Please find below a prospectus of the meeting and a preliminary draft program. If you are interested in participating and giving a contribution, please visit the web site http://www.mssl.ucl.ac.uk/~sz/Conference_files/index.html and follow the link "registration form" to submit an "expression of interest". If you find the above still under construction, please just send an e-mail to the soc at ns2006_science@majordomo.mssl.ucl.ac.uk (SOC) by specifying the kind of presentation (oral/poster). For non scientific inquiries related to local transport, accomodation and venue you can contact the loc at ns2006_local@majordomo.mssl.ucl.ac.uk (LOC) Best regards, The Scientific Organizing Committee A. Alpar (Turkey), F. Haberl (FRG), J. Horvath (Brasil), G.L. Israel (Italy), V. Kaspi (Canada), J. Lattimer (US), S. Mereghetti (Italy), C. Motch (France), D. Page (Mexico), G. Pavlov (US), C. Thompson (Canada), J. Truemper (FRG), R. Turolla (Italy, co-chair), S. Zane (UK, chair), V. Zavlin (US), D. Yakovlev (Russia) ------------------------------------------------------------------------- PROSPECTUS The very large majority of known neutron stars has been (and still is) discovered and studied in the radio band. However, the number of neutron stars detected at shorter wavelengths has been steadily increasing over the last decade. These sources yield crucial information on many different aspects of neutron star astrophysics which would have been otherwise inaccessible in radio pulsars. In particular, X-ray and optical observations of non-accreting neutron stars allow us to see direct emission from their surface layers which conveys information on the physical conditions of the star. In this respect, isolated neutron stars (i.e. those not in binary systems) play a key role and represent a unique laboratory for investigating the properties of matter under extreme conditions, such as the equation of state at supra-nuclear densities, the interaction of highly relativistic plasmas with radiation in the presence of ultra-strong magnetic fields and the theory of gravity. Furthermore, multiwavelength observations have revealed a variety of manifestations of neutron stars totally unexpected until a few years ago. Old neutron stars (age > 1 Myr) are too cold to be seen in X-rays, while the radiation from young active radio pulsars (age < 10,000 yr) is dominated by non-thermal emission from the magnetosphere surrounding the star. Several meetings have been devoted to various non-thermal emission mechanisms from neutron stars, and to the study of the interaction of the neutron star with its environmental plasma on the basis of observational data in the radio, optical and X-ray domains. Instead, our proposal is focused on the properties of the neutron star itself: the physics of surface and interior of neutron stars, mostly referring to high energy emission or X-ray data. A handful (less than 30) of detected X-ray sources are associated with middle-aged neutron stars and are luminous enough to be studied with current instruments. Each of them carries a wealth of invaluable information which awaits to be exploited. Besides these few radio-pulsars, surface emission has been detected to date from a number of radio-quiet neutron stars, which include the anomalous X-ray pulsars (AXPs), the so called X-ray dim isolated neutron stars (XDINSs), Geminga and Geminga-like objects, and possibly a few soft gamma-repeaters (SGRs). Thanks to last-generation ground-based and spaceborne observatories, an impressive amount of new data have been collected in the optical and X-rays over the last couple of years on these sources. In many cases these observations represented a genuine breakthrough in our knowledge of these objects. The excellent sensitivity in the soft X-ray band of the new telescopes on-board XMM-Newton and Chandra satellites provides an unprecedented spectral and timing resolution, allowing detailed phase-resolved spectroscopy and accurate period measurements to be carried out. Absorption features have been detected with high significance in one young radio quiet X-ray pulsar (1E1207-59), in a few (possibly older) XDINS, and during bursts of a SGR. Much progress has been obtained in the identification of optical/infrared counterparts of XDINS and AXPs. Hard tails extending beyond 100 keV have been discovered in AXPs and in one SGR with INTEGRAL and RXTE. The interpretation of many newly discovered properties of these sources represents a puzzle. Spin-down measurements in SGRs and AXPs favour the idea that these objects host a "magnetar", i.e. a neutron star with a magnetic field in excess of 10-100 Tera Gauss. The detection of a putative proton cyclotron line in SGR 1806-20 supports this scenario. The features detected in XDINs point towards quite large fields too. However, the reason why no cyclotron lines have been observed as yet from SGRs and AXPs in quiescence is still a mystery. So is the evolutionary link, if any, between these classes of sources. The recent X-ray detection of radio-pulsars with magnetic fields similar to those of AXPs but with much reduced X-ray luminosity brings in the possibility that highly magnetized neutron stars undergo transient phases of magnetar-like emission and radio activity. The almost perfect blackbody continuum of XDINSs challenges the predictions of conventional atmospheric models and bears directly to the determination of the star radius in these sources. Phase-resolved spectroscopy in AXPs and XDINs shows evidence of large spectral changes, and this, together with the large pulsed fractions, seems hardly compatible with a surface temperature distribution implied by a dipolar magnetic field. Observations of thermal radiation from the surfaces of isolated neutron stars enable one to check the theories of neutron star structure and evolution. Both the effective thermally emitting areas and the pulse profiles certainly contain information, which remain to be decoded, about the structure of the magnetic field in the surface layers and possibly even deep in the crust. The wide range of observed thermal luminosities, from SGRs down to XDINs and high-field radio pulsars, may be due to differences in stellar masses, and hence neutrino emission, and/or efficient internal heating mechanisms probably related to differences in the strength, topology, and evolution of their magnetic fields. This gives a powerful method to study the internal structure of neutron stars and to solve the long-standing fundamental problem of the equation of state at supra-nuclear densities in neutron star cores, exploring their composition (hyperons? pion or kaon condensates? deconfined quarks?), neutrino emission mechanisms and superfluid properties. A solution of this problem would have a strong impact on different branches of fundamental physics, including nuclear physics, physics of strong interactions and particle physics. For all these reasons it is our opinion that time is ripe for gathering together both observers and theoreticians working in this field. In this respect, we hope our meeting would offer a stimulating environment to review the current status-of-the-art, promote fruitful collaborations and discuss future perspectives in the post-XMM/Chandra era. LOCAL ORGANIZING COMMITTEE Silvia Zane (MSSL, UCL, UK) Katherine McGowan (MSSL, UCL, UK) Alex Blustin (MSSL, UCL, UK) Mark Cropper (MSSL, UCL, UK) Rosalind Medland (MSSL, UCL, UK) Libby Daghorn (MSSL, UCL, UK) Sue Russel (MSSL, UCL, UK) PRELIMINARY PROGRAM 1st day, Monday 24th April Morning 9.30-12.30 Overview AXPs and SGRs: Observations Afternoon 2.30-6.30 AXPs and SGRs: Observations 2nd day, Tuesday 25th April Morning 9.30-12.30 AXPs and SGRs: Magnetar and alternative models Afternoon 2.30-4.30 (Lecture Theatre to be vacated by 4.30 p.m.!) Poster Session 3rd day, Wed 26th April Morning 9.30-12.30 PSRs: Observations Afternoon 2.30-6.30 PSRs: Observations and models 4th day, Thu 27th April Morning 9.30-12.30 XDINSs: Observations Afternoon 2.30-6.30 XDINSs: Models 5th day, Fri 28th April Morning 9.30-12.30 Interior, EOSs Afternoon 2.30-6.30 Cooling models, comparison with observations Future perspectives DATES AND LOCATION: London, UK, April 24-28 2006 The meeting is sponsored by the Royal Astronomical Society (RAS), and the venue will be the Geological Society Lecture Theatre, near the Royal Academy of Arts (Burlington House) just a short walk from Piccadilly Circus and LeicesterSquare. http://www.ras.org.uk/index.php?option=content&task=view&id=226