The role of magnetic fields during the birth and death of stars
Zusammenfassung der Projektergebnisse
During the Emmy Noether project we have made several breakthroughs in our goal of determining the role of magnetic fields during massive star formation and in shaping late stellar outflows. Work during the project has for example shown that magnetic fields cannot be ignored during massive star formation as significant fields are detected in 33 out of 44 sources surveyed with the Effelsberg 100-m telescope. Follow-up observations of a number of these sources has also now shown that at the small scales, the magnetic field appears aligned with the large scale outflow. This is currently a major topic of research, as confirmation of this will put strong constraints on massive star formation theories. Additionally it is now clear that magnetically collimated outflows are the norm rather than the exception concerning the formation of bipolar planetary nebulae. This is largely due to our detection of a synchrotron jet from a post-AGB star. Our observations have also shown that large scale magnetic fields can be traced from the immediate circumstellar environment to the outer envelope. The project also led to several surprises. The unexpected detection of X-ray emission towards two evolved stars could indicate magnetic activity at the stellar surface. Alternatively, they are an indication of binary action that is thought to be the origin of strong circumstellar magnetic fields. Observations have recently been taken to measure the magnetic field for one of the X-ray sources. Unexpected binary activity was also found around the now-famous evolved star R Scl. Here, the binary motion has imprinted itself onto the molecular outflow, creating a spiral winding that can be traced for almost 2000 years back in time. Three results of the research in particular, have led to attention in the international press. The first one concerns the first proof of magnetically controlled accretion onto a protostellar disk around a massive young star. The press announcement can be found at http://www3.uni-bonn.de/Pressemitteilungen/041-2010 [in German] and https://www.ras.org.uk/news-and-press/news-archive/157-news2010/1732-massive-stars-magnetically-controlled-diets [in English]. The second one was based on the spiral structure discovered around R Scl, which led to numerous news items across the world. The original press release can be found at http://www.eso.org/public/news/eso1239/ Finally, our detection of a synchrotron jet also led to several news reports. For this result the English language release can be found at https://www.ras.org.uk/news-and-press/news-archive/224-news-2013/2341-magnetic-jet-shows-how-stars-begin-their-final-transformation
Projektbezogene Publikationen (Auswahl)
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“Methanol masers probing the ordered magnetic field of W75N”. 2009 Astronomy & Astrophysics, 506, 757
Surcis, G., Vlemmings, W.H.T., Dodson, R., van Langevelde, H.J.
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“Magnetic field regulated infall on a massive protostellar disc”. 2010 Monthly Notices of the Royal Astronomical Society, 404, 134
Vlemmings, W.H.T., Surcis, G., Torstensson, K.J., van Langevelde, H.J.
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“Magnetic fields in evolved stars: Imaging the polarized emission of highfrequency SiO masers”. 2011 Astrophysical Journal, 728, 149
Vlemmings, W.H.T., Humphreys, E.M.L., Franco-Hernández, R.
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“The structure of the magnetic field in the massive star-forming region W75N”. 2011 Astronomy & Astrophysics, 527, A48
Surcis, G., Vlemmings, W.H.T., Curiel, S., Hutawarakorn-Kramer, B., Torrelles, J.M., Sarma, A.P.
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“Zeeman splitting of 6.7 GHz methanol masers: On the uncertainty of magnetic field strength determinations”. 2011 Astronomy & Astrophysics, 529, A95
Vlemmings, W.H.T., Torres, R.M., Dodson, R.
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“Polarization of thermal molecular lines in the envelope of IK Tau”. 2012 Astronomy & Astrophysics, 540, L3
Vlemmings, W.H.T., Ramstedt, S., Rao, R., Maercker, M.
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“Rotten Egg Nebula: The magnetic field of a binary evolved star”. 2012 Astronomy & Astrophysics, 540, A42
Leal-Ferreira, M.L., Vlemmings, W.H.T., Diamond, P.J., Kemball, A.J., Amiri, N., Desmurs, J.-F.
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“Unexpectedly large mass loss during the thermal pulse cycle of the red giant star R Sculptoris”. 2012 Nature, 492, 232
Maercker, M., Mohamed, S., Vlemmings, W.H.T., Ramstedt, S., Groenewegen, M.A.T., Humphreys, E., Kerschbaum, F., Lindqvist, M., Olofsson, H., Paladini, C., Wittkowski, M., de Gregorio-Monsalvo, I., Nyman, L.-A.
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“A synchrotron jet from a post-AGB stars”, 2013, Monthly Notices of the Royal Astronomical Society, 436, 79
Pérez-Sánchez, A., F., Vlemmings, W.H.T., Tafoya, D., Chapman, J.M.
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“EVN observations of 6.7 GHz methanol maser polarization in massive starforming regions.II First statistical results”. 2013 Astronomy & Astrophysics, 556, 73
Surcis, G., Vlemmings, W.H.T., van Langevelde, H.J., Hutawarakorn Kramer, B., Quiroga-Nunez, L.H.
