Weak magnetic fields in central stars of planetary nebulae?

It is not yet clear whether magnetic fields play an essential role in shaping planetary nebulae (PNe), or whether stellar rotation alone and/or a close binary companion can account for the variety of the observed nebular morphologies. In a quest for empirical evidence verifying or disproving the role of magnetic fields in shaping PNe, we follow up on previous attempts to measure the magnetic field in a representative sample of PN central stars. We obtained low-resolution polarimetric spectra with FORS 2 at VLT for a sample of twelve bright central stars of PNe with different morphology, including two round nebulae, seven elliptical nebulae, and three bipolar nebulae. Two targets are Wolf-Rayet type central stars. For the majority of the observed central stars, we do not find any significant evidence for the existence of surface magnetic fields. However, our measurements may indicate the presence of weak mean longitudinal magnetic fields of the order of 100 Gauss in the central star of the young elliptical planetary nebula IC 418, as well as in the Wolf-Rayet type central star of the bipolar nebula Hen2-113 and the weak emission line central star of the elliptical nebula Hen2-131. A clear detection of a 250 G mean longitudinal field is achieved for the A-type companion of the central star of NGC 1514. Some of the central stars show a moderate night-to-night spectrum variability, which may be the signature of a variable stellar wind and/or rotational modulation due to magnetic features. We conclude that strong magnetic fields of the order of kG are not widespread among PNe central stars. Nevertheless, simple estimates based on a theoretical model of magnetized wind bubbles suggest that even weak magnetic fields below the current detection limit of the order of 100 G may well be sufficient to contribute to the shaping of PNe throughout their evolution.Comment: 16 pages, 11 figures, 3 tables, accepted for publication in A&A; References updated, minor correction

Magnetic fields in O-type stars measured with FORS1 at the VLT

The presence of magnetic fields in O-type stars has been suspected for a long time. The discovery of such fields would explain a wide range of well documented enigmatic phenomena in massive stars, in particular cyclical wind variability, Halpha emission variations, chemical peculiarity, narrow X-ray emission lines and non-thermal radio/X-ray emission. Here we present the results of our studies of magnetic fields in O-type stars, carried out over the last years.Comment: 2 pages, 1 figure, to appear in Proceedings of IAU Symposium 259 "Cosmic Magnetic Fields: from Planets, to Stars and Galaxies", Tenerife, Spain, November 3-7, 200

Abundance analysis, spectral variability, and search for the presence of a magnetic field in the typical PGa star HD19400

The aim of this study is to carry out an abundance determination, to search for spectral variability and for the presence of a weak magnetic field in the typical PGa star HD19400. High-resolution, high signal-to-noise HARPS spectropolarimetric observations of HD19400 were obtained at three different epochs in 2011 and 2013. For the first time, we present abundances of various elements determined using an ATLAS12 model, including the abundances of a number of elements not analysed by previous studies, such as Ne I, Ga II, and Xe II. Several lines of As II are also present in the spectra of HD19400. To study the variability, we compared the behaviour of the line profiles of various elements. We report on the first detection of anomalous shapes of line profiles belonging to Mn and Hg, and the variability of the line profiles belonging to the elements Hg, P, Mn, Fe, and Ga. We suggest that the variability of the line profiles of these elements is caused by their non-uniform surface distribution, similar to the presence of chemical spots detected in HgMn stars. The search for the presence of a magnetic field was carried out using the moment technique and the SVD method. Our measurements of the magnetic field with the moment technique using 22 Mn II lines indicate the potential existence of a weak variable longitudinal magnetic field on the first epoch. The SVD method applied to the Mn II lines indicates =-76+-25G on the first epoch, and at the same epoch the SVD analysis of the observations using the Fe II lines shows =-91+-35G. The calculated false alarm probability values, 0.008 and 0.003, respectively, are above the value 10^{-3}, indicating no detection.Comment: 13+6 pages, 14 figures, 6+1 tables, including the online-only material, accepted for publication in MNRA

Magnetic field geometry and chemical abundance distribution of the He-strong star CPD -57 3509

The magnetic field of CPD -57 3509 was recently detected in the framework of the BOB (B fields in OB stars) collaboration. We acquired low-resolution spectropolarimetric observations of CPD -57 3509 with FORS2 and high-resolution UVES observations randomly distributed over a few months to search for periodicity, to study the magnetic field geometry, and to determine the surface distribution of silicon and helium. We also obtained supplementary photometric observations at a timeline similar to the spectroscopic and spectropolarimetric observations. A period of 6.36d was detected in the measurements of the mean longitudinal magnetic field. A sinusoidal fit to our measurements allowed us to constrain the magnetic field geometry and estimate the dipole strength in the range of 3.9-4.5kG. Our application of the Doppler imaging technique revealed the presence of He I spots located around the magnetic poles, with a strong concentration at the positive pole and a weaker one around the negative pole. In contrast, high concentration Si III spots are located close to the magnetic equator. Further, our analysis of the spectral variability of CPD -57 3509 on short time scales indicates distinct changes in shape and position of line profiles possibly caused by the presence of beta Cep-like pulsations. A small periodic variability in line with the changes of the magnetic field strength is clearly seen in the photometric data.Comment: 11 pages, 5 tables, 7 figures, accepted for publication in MNRA

First measurement of the magnetic field on FK Com and its relation to the contemporaneous star-spot locations

In this study, we present simultaneous low-resolution longitudinal magnetic field measurements and high-resolution spectroscopic observations of the cool single giant FK Com. The variation of the magnetic field over the rotational period of 2.4 d is compared with the star-spot location obtained using Doppler imaging techniques, V-band photometry and V−I colours. The chromospheric activity is studied simultaneously with the photospheric activity using high-resolution observations of the Hα, Hβ and Hγ line profiles. Both the maximum (272 ± 24 G) and minimum (60 ± 17 G) in the mean longitudinal magnetic field, 〈Bz〉, are detected close to the phases where cool spots appear on the stellar surface. A possible explanation for such a behaviour is that the active regions at the two longitudes separated by 0.2 in phase have opposite polaritie

On the robustness of gender differences in economic behavior

This is the final version. Available on open access from Nature Research via the DOI in this recordData and code availability: The dataset generated and analyzed for this research project as well as the custom code that supports the study′s findings are available on OSF (https://osf.io/tyzjh/?view_only=243e2b6ca1174a8d802f496ce97c6a70). The oTree code is available on request.Because of the importance of economic decisions, researchers have looked into what factors influence them. Gender has received a lot of attention for explaining differences in behavior. But how much can be associated with gender, and how much with an individual's biological sex? We run an experimental online study with cis- and transgender participants that (1) looks into correlational differences between gender and sex for competitiveness, risk-taking, and altruism by comparing decisions across these different subject groups. (2) we prime participants with either a masculine or feminine gender identity to examine causal gender effects on behavior. We hypothesize that if gender is indeed a primary factor for decision-making, (i) individuals of the same gender (but different sex) make similar decisions, and (ii) gender priming changes behavior. Based on 780 observations, we conclude that the role of gender (and sex) is not as decisive for economic behavior as originally thought.Elite Network of BavariaBavarian State Ministry of Science and the ArtsUniversity of Exeter Business Schoo

The magnetic field and the evolution of element spots on the surface of the HgMn eclipsing binary AR Aur

The system AR Aur is a young late B-type double-lined eclipsing binary with a primary star of HgMn peculiarity. We applied the Doppler imaging method to reconstruct the distribution of Fe and Y over the surface of the primary using spectroscopic time series obtained in 2005 and from 2008 October to 2009 February. The results show a remarkable evolution of the element distribution and overabundances. Measurements of the magnetic field with the moment technique using several elements reveal the presence of a longitudinal magnetic field of the order of a few hundred gauss in both stellar components and a quadratic field of the order of 8 kG on the surface of the primary star.Fil: Hubrig, S.. Astrophysikalisches Institut Potsdam; AlemaniaFil: Savanov, I.. Russian Academy of Sciences. Institute of Astronomy; RusiaFil: Ilyin, I.. Astrophysikalisches Institut Potsdam; AlemaniaFil: Gonzalez, Jorge Federico. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; ArgentinaFil: Korhonen, H.. European Southern Observatory; AlemaniaFil: Lehmann, H.. Thuringer Landessternwarte; AlemaniaFil: Schöller, M.. European Southern Observatory; AlemaniaFil: Granzer, T.. Astrophysikalisches Institut Potsdam; AlemaniaFil: Weber, M.. Astrophysikalisches Institut Potsdam; AlemaniaFil: Strassmeier, K. G.. Astrophysikalisches Institut Potsdam; AlemaniaFil: Hackman, T.. Thuringer Landessternwarte; AlemaniaFil: Tkachenko, A.. Thuringer Landessternwarte; Argentin