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Massive Stars and High-Energy Emission in OB Associations Massive Stars and High-Energy Emission in OB Associations Proceedings of JENAM 2005 Distant Worlds, July 4-7, 2005, Liège (Belgium) Images © ESA, ESO, NASA. Institut d‘Astrophysique et de Géophysique Edited by: Université de Liège G. Rauw, Y. Nazé, Allée du 6 Août 17, Bat. B5C R. Blomme & E. Gosset B4000-Liège (Belgium) Dépôt légal : D/2005/0480/95 Foreword About 35 astronomers including many experts in the field of massive stars attended the afternoon sessions of the JENAM 2005 workshop —Massive Stars and High-Energy Emission in OB Associations“. In addition to the two plenary talks by Dr Ian Stevens and Prof Thierry Montmerle, two invited reviews by Prof Artemio Herrero and Dr Martin Guerrero as well as 12 contributed talks and nine posters were presented during the workshop. A good number of new exciting results obtained with modern high-resolution optical spectrographs and/or high-energy instruments onboard XMM-Newton, Chandra and INTEGRAL were presented and new questions were raised. Several contributions were devoted to non-thermal phenomena associated with a subset of the massive stars. Many results presented at the workshop seem to demonstrate that non-thermal radio emission of early-type stars is a signature of colliding winds in binary systems. W hile this was already established for W olf-Rayet stars, it becomes now more and more obvious for O stars as well. In this context, the participants emphasized the interest to search for non-thermal X-ray and G- ray emissions from massive binaries. Such a hard X-ray œ soft G-ray emission could also arise from the collision of a supernova remnant with a stellar wind. The topic of non-thermal emission is related to one of the most controversial issues of massive star research; their magnetic fields. Magnetic fields certainly play a major role in the generation of the non-thermal radio emission and they might lead to magnetically confined stellar winds (such as observed in K Ori C). However, there are many questions that remain open as to the origin of these fields, their strengths as well as their origin (fossil vs. dynamo… ). These properties are essential ingredients of any theoretical attempt to model the non-thermal processes. The participants expressed their hope that upcoming observational facilities as well as new developments in theoretical models will allow to better constrain the properties of magnetic fields in early-type stars. New questions were also raised concerning the origin of X-ray emission from massive stars. Some observational as well as theoretical results cast doubt on the —standard model“ (the shock œ X- ray emission paradigm) for the production of X-rays from massive stars. Again, magnetic fields might play a key role here. Another major question concerns the duplicity of massive stars and the colliding wind phenomenon. As a result of detailed analyses and high-quality data, we now have better statistics of the multiplicity of massive stars as well as a better knowledge of the observed properties of colliding wind systems over a broad range of stellar parameters. Some features were unexpected, others agree quite well with theoretical expectations. A question that was actively debated is whether or not all W olf-Rayet stars that emit X-rays or that produce dust are binaries. Finally, wind- wind collisions or magnetic fields might also play a role in the enigmatic variability of some peculiar objects like the Of?p stars. Some topics related to star formation were also discussed. Recent X-ray observations of massive star clusters reveal a wealth of secondary sources associated with pre-main sequence stars. A new temperature calibration of O-type stars further suggests that massive stars are significantly cooler than previously thought and may actually not appear on the zero age main sequence. These results are crucial for a better understanding of massive star formation and of many interaction processes between massive stars and their surroundings. The participants of the workshop emphasized the need for more observations of massive stars in the high-energy domain (using XMM-Newton, INTEGRAL and Chandra) as well as in the radio domain and they decided to coordinate their efforts towards this endeavor. It is our pleasure to thank Jean-Pierre Swings and Jean-Marie Vreux for their participation in the local organizing committee of this workshop, as well Denise Caro, Alain Detal and Sandrine Sohy who contributed significantly to the practical organization of the workshop. The organization of the JENAM 2005 event was made possible through various grants received from the —Province de Liège“, OPTICON, the European Astronomical Society (EAS), the European Space Agency (ESA), AMOS, the —Fonds National de la Recherche Scientifique“ (FNRS), the Belgian Science Policy (Belspo), the —Université de Liège“ and the —Communauté Française de Belgique“. W e are grateful to all these organizations for their financial support. An electronic version of these proceedings is available at the link http://www.astro.ulg.ac.be/RPub/Colloques/JENAM/proceedings/proceedings.html Liège, November 2005 Gregor Rauw, Yaël Nazé, Ronny Blomme, Eric Gosset Table of Contents Sect. 1: Massive stars: general properties, X-ray emission and peculiar objects Plenary Talk X-ray and gamma-ray emission from single and binary early-type stars I.R. Stevens … … … … … … … … … … … L L L 0L L L L L 000L L L L L L L L L L 00L < Invited Talks X-ray survey of Wolf-Rayet stars in the Magellanic Clouds 00 (, & Y.-H. Chu .… … … … … … … … .… … L L L L L L L L L L L L 00L .< Parameters of massive stars in the Milky Way and nearby galaxies 0 @o, & F. Najarro… … … … … … … … … … … … L L 0000L L L L L L L L L 00L 00. Contributed Talks The peculiar Of?p stars HD108 and HD191612 60 /7) (0 4auw, N.R. W alborn, & I.D. Howarth … … ...… … … … ...… … … … … … … … 31 A new paradigm for the X-rays from O-stars A.M.T. Pollock, & A.J.J. Raassen… ...… … … … … … … … … … … … ...… … … … … … … … 35 Posters CN status of a sample of galactic OB supergiants M. Sarta Dekoviş, & D. Kotnik-Karuza… … … … … … … … … … … … … … … … … … … … .39 Sect. 2: Colliding winds and non-thermal emission Contributed Talks Observations of non-thermal radio emission in O-type stars R. Blomme..… … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … 45 Radio emission from colliding-wind binaries: observations and models S.M. Dougherty, J.M. Pittard, & E.P. O‘Connor..… … … … … … … … … … … … … … … … .49 The XMM-Newton view of Plaskett's star and its surroundings N. Linder, & G. Rauw… ..… … … … … … … … … … … … … … … … … … … … … … … … … ..53 Non-thermal X-ray and gamma-ray emission from the colliding-wind binary WR140 J.M. Pittard, & S.M. Dougherty...… … … … … … … … … … … … … … … … … … … … … … ..57 Can single O-stars produce non-thermal radio emission? Or are they binaries? S. Van Loo… .… … … … … … … … … … … … … … … … … … … … … … … … … … … … … … .61 Are WC9 Wolf-Rayet stars in colliding-wind binaries? P.M. W illiams, K.A. van der Hucht, & G. Rauw… … … … … … … … … … … … … … … … ...65 Posters X-ray analysis of the close binary system FO15 J.F. Albacete Colombo, & G. Micela… … … … … … … … … … … … … … … … … … … … … .69 Evidence for phase-locked X-ray variations from the colliding wind massive binary Cyg OB2 #8a M. De Becker, & G. Rauw… … … … … … … … … … … … … … … … … … … … … L L L L 0< Preliminary results of an observational campaign aiming at the study of the binary system LSS3074 E. Gosset, G. Rauw, J. Manfroid, E. Antokhina, I.R. Stevens, & H. Sana… … … … … … … 77 The colliding winds of WR146: seeing the works E.P. O'Connor, S.M. Dougherty, J.M. Pittard, & P.M. W illiams… .… … … … … … … … … ..81 On the multiplicity of the non-thermal radio emitters 9 Sgr and HD168112 G. Rauw, H. Sana, E. Gosset, M. De Becker, J. Arias, N. Morrell, P. Eenens, & D. Stickland … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … 85 CPD-41°7742: an unusual wind interaction H. Sana, E. Gosset, G. Rauw, E. Antokhina, P. Royer, J. Manfroid, & J.-M. Vreux.… … ...89 Sect. 3: High-energy emission from young open clusters Contributed Talks Energetic processes and non-thermal emission of star forming complexes A.M. Bykov… … … … … … … … … … … … … … … … … … … … … … … … … … … … .… … ...95 X-raying the super star clusters in the Galactic center L.M. Oskinova ...… … … … … … … … … … … … … … … … … … … … … … … … … … … … … 99 XMM-Newton observations of the Cyg OB2 association G. Rauw, M. De Becker, & N. Linder… ..… … … … … … … … … … … … … … … … … … … 103 The young open cluster NGC6231: five years of investigations H. Sana, G. Rauw, & E. Gosset… ..… … … … … … … … … … … … … … … … … … … … … ..107 Posters A spectroscopic investigation of the young open cluster IC1805 M. De Becker, & G. Rauw… … … … … … … … … … … … … … … … … … … … … … … .… ..111 A survey for gamma-ray emission from OB associations with INTEGRAL: some preliminary results J.-C. Leyder, & G. Rauw..… … … … … … … … … … … … … … … … … … … … … … … … … 115 Section 1 Massive stars: general properties, X-ray emission and peculiar objects X-ray and gamma-ray emission from single and binary early-type stars I.R. Stevens School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK Abstract: Since their launch, both the Chandra and XMM-Newton satellites have provided us with a new and more detailed view of the high energy processes in massive stars. This paper reviews recent X-ray observations of a range of massive stars, both O-stars and Wolf-Rayet (W-R) stars, as well as both single early-type stars and
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