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The number of magnetic stars detected among massive stars is small; nevertheless, the role played by the magnetic field in stellar evolution cannot be disregarded. Links between line profile variability, enhancements/depletions of surface chemical abundances, and magnetic fields have been identified for low-mass B-stars, but for the O-type domain this is almost unexplored. Based on FORS 2 and HARPS spectropolarimetric data, we present the first detection of a magnetic field in HD54879, a single slowly rotating O9.7 V star. Using two independent and different techniques we obtained the firm detection of a surface average longitudinal magnetic field with a maximum amplitude of about 600 G, in modulus. A quantitative spectroscopic analysis of the star with the stellar atmosphere code FASTWIND results in an effective temperature and a surface gravity of 33 000 +/- 1000K and 4.0 +/- 0.1 dex. The abundances of carbon, nitrogen, oxygen, silicon, and magnesium are found to be slightly lower than solar, but compatible within the errors. We investigate line-profile variability in HD54879 by complementing our spectra with spectroscopic data from other recent OB-star surveys. The photospheric lines remain constant in shape between 2009 and 2014, although H alpha shows a variable emission. The H alpha emission is too strong for a standard O9.7 V and is probably linked to the magnetic field and the presence of circumstellar material. Its normal chemical composition and the absence of photospheric line profile variations make HD54879 the most strongly magnetic, non-variable single O-star detected to date.
Only a small fraction of massive stars seem to host a measurable structured magnetic field, whose origin is still unknown and whose implications for stellar evolution still need to be assessed. Within the context of the "B fields in OB stars (BOB)" collaboration, we used the HARPSpol spectropolarimeter to observe the early B-type stars beta CMa (HD 44743; B1 II/III) and epsilon CMa (HD 52089; B1.5II) in December 2013 and April 2014. For both stars, we consistently detected the signature of a weak (<30 G in absolute value) longitudinal magnetic field, approximately constant with time. We determined the physical parameters of both stars and characterise their X-ray spectrum. For the beta Cep star beta CMa, our mode identification analysis led to determining a rotation period of 13.6 +/- 1.2 days and of an inclination angle of the rotation axis of 57.6 +/- 1.7 degrees, with respect to the line of sight. On the basis of these measurements and assuming a dipolar field geometry, we derived a best fitting obliquity of about 22 degrees and a dipolar magnetic field strength (B-d) of about 100 G (60 < B-d < 230 G within the 1 sigma level), below what is typically found for other magnetic massive stars. This conclusion is strengthened further by considerations of the star's X-ray spectrum. For epsilon CMa we could only determine a lower limit on the dipolar magnetic field strength of 13 G. For this star, we determine that the rotation period ranges between 1.3 and 24 days. Our results imply that both stars are expected to have a dynamical magnetosphere, so the magnetic field is not able to support a circumstellar disk. We also conclude that both stars are most likely core hydrogen burning and that they have spent more than 2/3 of their main sequence lifetime. A histogram of the distribution of the dipolar magnetic field strength for the magnetic massive stars known to date does not show the magnetic field "desert" observed instead for intermediate-mass stars. The biases involved in the detection of (weak) magnetic fields in massive stars with the currently available instrumentation and techniques imply that weak fields might be more common than currently observed. Our results show that, if present, even relatively weak magnetic fields are detectable in massive stars and that more observational effort is probably still needed to properly access the magnetic field incidence.
Portal Wissen = Cosmos
(2018)
Speaking of the cosmos means speaking about nothing less than everything, about the entirety of space filled with matter and energy. We only see a tiny fraction of it from Earth: planets like Venus or stars like the Sun. There are at least 100 billion stars in our home galaxy alone. Bound by gravity, these luminescent celestial bodies of very hot gas form a system visible from Earth as a whitish ribbon, which we call the Milky Way. The observable cosmos contains at least 100 billion such galaxies with stars, cosmic dust, gas, and probably dark matter as well. The universe is 13.8 billion years old; crossing it once would probably take 78 billion light-years.
Given these dimensions, it is hardly surprising that for us humans, the mystery of the properties of the cosmos is connected with questions of being. Where do we come from? Where are we going? Are we alone in the universe? Such questions are in the wheelhouse of astrophysicists, who explore the vastness of the cosmos through physical means, even though they, of course, deal with physical laws, mathematical formulas, and complicated measuring methods. In this issue of Portal Wissen, we talked with astrophysicists at the University of Potsdam about their research and everyday work.
Lutz Wisotzki showed us a 3D spectrograph, which he has developed in collaboration with colleagues from the Leibniz Institute for Astrophysics (AIP) and six other European institutes. This technical masterpiece enables scientists to look deeply into space and to “journey” through time to galaxies shortly after the Big Bang. Philipp Richter introduced us to the astrophysics research initiative and demonstrated how the University of Potsdam is working together with the AIP, the Albert Einstein Institute (AEI) and the Deutsches Elektronen-Synchrotron (DESY) to train junior researchers. The newly appointed Professor of Stellar Astrophysics, Stephan Geier, presented us with stars so close together to each other that they appear to be one to the naked eye. The physicist, who is also a historian, researches their turbulent relationships.
We have not confined ourselves to cosmic themes, though, but also questioned rather earthly matters such as modern consumption. We have thought about potential love relationships with robots and testimonials in literature and art. We learned why the rainforest in Central Africa disappeared 2,600 years ago, how to produce knee prostheses on a production line, and how animals in the field benefit from big data.
But back to the cosmos. The writing of late astrophysicist Stephen Hawking fundamentally shaped our concepts and knowledge of the universe. And that is because he was both an important physicist and a literary genius. Hardly anyone has been able to capture difficult facts in such a clear, understandable, and beautiful language. With this exemplary understanding of science in mind, we hope to offer you a stimulating read.
The Editors
The B fields in OB stars (BOB) survey is an ESO large programme collecting spectropolarimetric observations for a large number of early-type stars in order to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. As of July 2014, a total of 98 objects were observed over 20 nights with FORS2 and HARPSpol. Our preliminary results indicate that the fraction of magnetic OB stars with an organised, detectable field is low. This conclusion, now independently reached by two different surveys, has profound implications for any theoretical model attempting to explain the field formation in these objects. We discuss in this contribution some important issues addressed by our observations (e.g., the lower bound of the field strength) and the discovery of some remarkable objects.
When dealing with issues that are of high societal relevance, Earth sciences still face a lack of acceptance, which is partly rooted in insufficient communication strategies on the individual and local community level. To increase the efficiency of communication routines, science has to transform its outreach concepts to become more aware of individual needs and demands. The “encoding/decoding” concept as well as critical intercultural communication studies can offer pivotal approaches for this transformation.
When dealing with issues that are of high so-cietal relevance, Earth sciences still face a lack of accep-tance, which is partly rooted in insufficient communicationstrategies on the individual and local community level. Toincrease the efficiency of communication routines, sciencehas to transform its outreach concepts to become more awareof individual needs and demands. The “encoding/decoding”concept as well as critical intercultural communication stud-ies can offer pivotal approaches for this transformation.
A lasting legacy of the International Polar Year (IPY) 2007–2008 was the promotion of the Permafrost Young Researchers Network (PYRN), initially an IPY outreach and education activity by the International Permafrost Association (IPA). With the momentum of IPY, PYRN developed into a thriving network that still connects young permafrost scientists, engineers, and researchers from other disciplines. This research note summarises (1) PYRN’s development since 2005 and the IPY’s role, (2) the first 2015 PYRN census and survey results, and (3) PYRN’s future plans to improve international and interdisciplinary exchange between young researchers. The review concludes that PYRN is an established network within the polar research community that has continually developed since 2005. PYRN’s successful activities were largely fostered by IPY. With >200 of the 1200 registered members active and engaged, PYRN is capitalising on the availability of social media tools and rising to meet environmental challenges while maintaining its role as a successful network honouring the legacy of IPY.