The X-ray MEGA Campaign on Hot Stars

Introduction

The Einstein, ROSAT and ASCA X-ray observatories have made substantial progress in the understanding of X-ray emission from massive stars, having established (for example) that the observed X-ray luminosity is proportional to stellar bolometric luminosity for the OB stars, or that X-ray variability is relatively rare among massive stars, or that X-ray emission from Wolf-Rayet stars shows unexpectedly large amounts of scatter in their Lx/Lbol relation, or that binary systems like WR 140 and Gamma2 Vel show evidence of X-ray emitting gas produced by the collision of stellar winds. New observations with the Chandra and XMM-Newton X-ray observatories are greatly expanding these discoveries. These observations have also raised many unresolved questions: why are some binaries X-ray variables and some not? What causes the scatter in Lx/Lbol for the WR stars? Why are LBVs weak X-ray sources ? When is X-ray emission from colliding winds important, and what does that tell us about the nature of the stellar winds in binaries? In addition, modern X-ray observatories raise the exciting possibility to use X-ray emission as a tool to address fundamental questions about the dynamics and chemistry of stellar winds. The time has come to build on the initial inroads with a dedicated program of X-ray observations which can address these issues. The "MEGA" Campaign has been formed by scientists with interest in developing a full understanding of the phenomena of X-ray emission from hot stars.

Group Members

Co-Investigators in this project are Bruce Altner (QSS), Dominique Ballereau (Meudon), Rodolfo Barba, Virpi Niemela, Nidia Morrell and Albacete Colombo juan Facundo (UNLP), Thomas Berghoefer (Hamburg), David Cohen (Swarthmore), Mike Corcoran (USRA), Augusto Damineli (IAGUSP), Philippe Eenens (Guanajuato), Thomas Eversberg, Yoshitomo Maeda (Penn State), Anita Mücke, Sergey Marchenko, Tony Moffat, Nicole St.-Louis, and Gwen Skalkowski (Montreal), David Florkowski (USNO), Ken Gayley (Iowa), Doug Gies (GSU), Kazunori "Bish" Ishibashi (GSFC), Kenji Kawashima, Kenzo Kinugasa, Shunji Kitamoto, Takashi Toneri, and Ken-ichi Torii (Osaka), Gloria Koenigsberger (UNAM), Yoji Kondo (GSFC), Danny Lennon, Rolf Kudritzki and Ralf Palsa (Munich), Siegfried Lührs (Münster), Anthony Marston (IPAC), Felix Mirabel (Saclay), John Monnier (CFA), Nancy Morrison (Toledo), Joy Nichols (CFA), Stan Owocki and Vikram Dwarkadas (Bartol), Julian Pittard (Leeds) Andy Pollock (C & S Ltd), Gregor Rauw, Jean-Marie Vreux and Yael Naze (Liege), Karel van der Hucht (SRON), Ram Sagar (IIAP), Werner Schmutz (ETHZ), Ian Stevens (Birmingham), Michelle Thaller (IPAC), Olga Tsiopa (Pulkova), Vladimir Usov (Weizmann), Roberto Viotti (IAS), Gregg Wade (Toronto), Wayne Waldron (ARD), Ulf Wessolowski (MPE), Stephen White (UMd), Peredur Williams (ROE), and Juan Zorec (IAP).

Published Papers

"ASCA spectroscopy of the hard X-ray emission from the colliding wind interaction in Gamma2 Velorum", G. Rauw, I. R. Stevens, J. M. Pittard, M. F. Corcoran, 2000, MNRAS, 316, 129.
"Coordinated monitoring of the eccentric O-star binary Iota Orionis: optical spectroscopy and photometry", Sergey V. Marchenko, Gregor Rauw, Eleonora A. Antokhina, Igor I. Antokhin, Dominique Ballereau, Jacques Chauville, Michael F. Corcoran, Rafael Costero, Juan Echevarria, Thomas Eversberg, Ken G. Gayley, Gloria Koenigsberger, Anatoly S. Miroshnichenko, Anthony F. J. Moffat, Nidia I. Morrell, Nancy D. Morrison, Christopher L. Mulliss, Julian M. Pittard, Ian R. Stevens, Jean-Marie Vreux, and Jean Zorec, 2000, MNRAS, 317, 333.
"Coordinated monitoring of the eccentric O-star binary Iota Orionis: the X-ray analysis", Julian M. Pittard, Ian R. Stevens, Michael F. Corcoran, Ken G. Gayley, Sergey V. Marchenko, and Gregor Rauw, 2000, MNRAS, 319, 137.
"Optical spectroscopy of X-MEGA targets I. CPD -59 2635: A New Double-Lined O type Binary in the Carina Nebula", J.F. Albacete Colombo, N.I. Morrell, V.S. Niemela, and M.F. Corcoran, 2001, MNRAS, 326, 78.
"Optical spectroscopy of X-Mega targets in the Carina Nebula. II. The massive double-lined O-type binary HD 93205", N.I. Morrell, R.H. Barbá, V.S. Niemela, M.A. Corti, J.F. Albacete Colombo, G. Rauw, M. Corcoran, T. Morel, J.-F. Bertrand, A.F.J. Moffat, and N. St-Louis, 2001, MNRAS, 326, 85.
"High Resolution X-ray Imaging of the Colliding Wind Shock in WR147", J. M. Pittard, I. R. Stevens, P. M. Williams, A. M. T. Pollock, S. L. Skinner, M. F. Corcoran, and A. F. J. Moffat, 2002, A&A, in press.
"Galactic Starburst NGC 3603 from X-rays to Radio", A.F.J. Moffat, M.F. Corcoran, I.R. Stevens, G. Skalkowski, S.V. Marchenko, A. Mücke, A. Ptak, B.S. Koribalski, L. Brenneman, R. Mushotzky, J.M. Pittard, A.M.T. Pollock, and W. Brandner, 2002, ApJ, 573, 191.
"Optical spectroscopy of X-Mega targets Ð IV. CPD -59 2636: a new O-type multiple system in the Carina Nebula", J. F. Albacete Colombo, N. I. Morrell, G. Rauw, M. F. Corcoran, V. S. Niemela and H. Sana, 2002, MNRAS,336, 1099.
"An X-Ray Investigation of the NGC 346 Field in the Small Magellanic Cloud I. The Luminous Blue Variable HD 5980 and the NGC 346 Cluster", Y. Nazé, J. M. Hartwell and I. R. Stevens, M. F. Corcoran, Y.-H. Chu, G. Koenigsberger, A. F. J. Moffat and V. S. Niemela, 2002 ApJ 580 225.

Current Projects

NGC 346.
- We obtained a 100 ksec observation of NGC 346 with the CHANDRA ACIS camera on May 15, 2001 (orbital phase 0.23)
- We obtained a 27 ksec observation of HD 5980/NGC 346 with XMM-Newton on November 21, 2001 (orbital phase 0.09)
NGC 3603. We obtained a 50 ksec observation of NGC 3603, a "starburst" region in the Milky Way, with the CHANDRA ACIS camera on May 1 2000. We expect that the processed data will be available in Jun 2000, but the quicklook image is available. Details of the observation from the CHANDRA AO1 target timeline are available. The proposal is available to XMEGA members. There is a preprint available of a paper which has been accepted by the ApJ.

Previous Projects

Join US!

If you'd like to be part of this endeavour, please contact Mike Corcoran (corcoran@barnegat.gsfc.nasa.gov).