The coupling between the convective region in the envelope and rotation can produce a surface latitudinal differential rotation that may induce changes of the stellar geometry and on the spectral line profiles that it may be scrutinized spectroscopically and by interferometry.

The presence of magnetic fields at the surfaces of many massive stars has been suspected for decades, to explain the observed properties and activity of OB stars. However, very few genuine high-mass stars had been identified as magnetic before the advent of a new generation of powerful spectropolarimeters that has resulted in a rapid burst of precise information about the magnetic properties of massive stars. During this talk, I will briefly review modern methods used to diagnose magnetic fields of higher-mass stars, and summarize our current understanding of the magnetic properties of OB stars.

The Magnetism in Massive Stars (MiMeS) Project is a consensus collaboration among many of the foremost international researchers of the physics of hot, massive stars, with the basic aim of understanding the origin, evolution and impact of magnetic fields in these objects. At the time of writing, MiMeS Large Programs have acquired over 950 high-resolution polarised spectra of about 150 individual stars with spectral types from B5-O4, discovering new magnetic fields in a dozen hot, massive stars. The quality of this spectral and magnetic matériel is very high, and the Collaboration is keen to connect with colleagues capable of exploiting the data in new or unforeseen ways. In this paper we review the structure of the MiMeS observing programs and report the status of observations, data modeling and development of related theory.

This paper presents results obtained from Stokes I and V spectra of the B2Vp star sigma Ori E, observed by both the Narval and ESPaDOnS spectropolarimeters. Using Least-Squares Deconvolution, we investigate the longitudinal magnetic field at the current epoch, including period analysis exploiting current and historical data. σ Ori E is the prototypical helium-strong star that has been shown to harbor a strong magnetic field, as well as a magnetosphere, consisting of two clouds of plasma forced by magnetic and centrifugal forces to co-rotate with the star on its 1.19 day period. The Rigidly Rotating Magnetosphere (RRM) model of Townsend & Owocki (2005) approximately reproduces the observed variations in longitudinal field strength, photometric brightness, Hα emission, and various other observables. There are, however, small discrepancies between the observations and model in the photometric light curve, which we propose arise from inhomogeneous chemical abundances on the star's surface. Using Magnetic Doppler Imaging (MDI), future work will attempt to identify the contributions to the photometric variation due to abundance spots and due to circumstellar material.

For early type magnetic stars slow, at most moderate rotational velocities have been considered an observational fact. The detection of a multi-kilogauss magnetic field in the B2Vpn star with P ≈ 0.52 d and v sin i ≈ 300 km/s has brought down this narrative. We have obtained more than 100 high-resolution, high-S/N echelle spectra in 2009. These spectra provide the most detailed description of the variability of any He-strong star to date. The circumstellar environment is dominated by a rotationally locked magnetosphere out to several stellar radii, causing hydrogen emission. The photosphere is characterized by surface chemical abundance inhomogeneities, with much stronger amplitudes, at least for helium, than slower rotating stars like σ Ori E. The highly complex rotational line profile modulations of metal lines are probably a consequence the equatorial gravity darkening of HR 7355, and thus may offer an independent measurement of the von Zeipel parameter β.

This review describes the observational evidence for structure in the winds of O-type stars due to large-scale perturbations and small-scale inhomogeneities. Despite considerable progress, a comprehensive theoretical framework that explains the origin. properties, and coexistence of wind structure on different spatial scales has yet to be constructed and incorporated into model atmosphere analyses. Consequently, it is not yet possible to assess the effect of non-stationary structures on different wind diagnostics in a rigorous way, with the result that accurate empirical determinations of mass-loss rates remain elusive.

After briefly reviewing the theory behind the radiative line-driven winds of OB stars, I examine the processes that can generate structure in them; these include both intrinsic instabilities, and surface perturbations such as pulsation and rotation. I then delve into wind channeling and confinement by magnetic fields as a mechanism for forming longer-lived circumstellar structures. With a narrative that largely follows the historical progression of the field, I introduce the key insights and results that link the first detection of a magnetosphere, over three decades ago, to the recent direct measurement of magnetic braking in a number of active OB stars.

In this talk, I review the different MHD processes, which take place in massive star interiors. First, I describe MHD instabilities, which act on magnetic fields in stellar radiation zones, and the dynamo action in massive stars that give strong indications in favor of a fossil origin of the fields observed at the surface of these stars. Then, I discuss the study of MHD turbulent relaxation processes, which are now examined in stellar interiors, to describe initial conditions for fossil magnetic fields. Finally, I focus on the state of the art of the modeling of the interaction between differential rotation, fossil magnetic field, meridional circulation, and turbulence.

Doppler imaging of early-type magnetic stars is the most advanced method to interpret their line profile variations. DI allows us to study directly a complex interplay between chemical spots, magnetic fields, and the mass loss. Here we outline the general principles of the surface mapping of stars, discuss adaption of this technique to early-type stars and present several recent examples of the abundance and magnetic mapping performed for rapidly rotating early-B stars. In particular, we present the first Doppler images for the very fast rotating He-rich star HR 7355 and a reconstruction of magnetic field for the well-known Bp star σ Ori E. We also present new magnetic maps for the He-strong star HD 37776, which possesses one of the most complex magnetic field topologies among the upper main sequence stars.

The discussion on winds and magnetic fields of active OB stars was carried out by S. Owoki, G. Wade, M. Cantiello, O. Kochukhov, M. Smith, C. Neiner, T. Rivinius, H. Henrichs and R. Townsend. The topics were the ability to detect small and large scale magnetic fields in massive stars and the need to consider limits on photometric variability of the star surface brightness.

We review the status of a long-term program to search for stellar magnetospheres in Bp stars. A few new σOri E analogues discovered during the course of this investigation are briefly discussed and other stars that may be worthy of further study are noted.

We conduct 3D magneto-hydrodynamic (MHD) simulations in order to test the stability of the magnetic equilibrium configuration described by Duez & Mathis (2010). This analytically-derived configuration describes the lowest energy state for a given helicity in a stellar radiation zone. The necessity of taking into account the non force-free property of the large-scale, global field is here emphasized. We then show that this configuration is stable. It therefore provides a useful model to initialize the magnetic topology in upcoming MHD simulations and stellar evolution codes taking into account magneto-rotational transport processes.

We report recent observations of the sharp-lined magnetic βCep pulsator ξ1 CMa (= HD 46328). The longitudinal magnetic field of this star is detected consistently, but it is not observed to vary significantly, during nearly 5 years of observation. In this poster we evaluate whether the constant longitudinal field is due to intrinsically slow rotation, or rather if the stellar or magnetic geometry is responsible.

Spectropolarimetric observations of HD 155806 – the hottest Galactic Oe star – were obtained with CFHT/ESPaDOnS to test the hypothesis that disk signatures in its spectrum are due to magnetic channeling and confinement of its stellar wind. We did not detect a dipole field of sufficient strength to confine the wind, and could not confirm previous reports of a magnetic detection. It appears that stellar magnetism is not responsible for producing the disk of HD 155806.

The line driven- and rotation modulated-wind theory predicts an alternative slow solution, besides from the standard m-CAK solution, when the rotational velocity is close to the critical velocity. We study the behaviour of the winds of A-type supergiants (Asg) and show that under particular conditions, e.g., when the δ line-force parameter is about 0.25, the slow solution could exist over the whole star, even for the cases when the rotational speed is slow or zero. We discuss density and velocity profiles as well as possible observational conterparts.

We present the results of a recent survey of cool, late-type supergiants - the descendants of massive O- and B-type stars - that has systematically detected magnetic fields in these stars using spectropolarimetric observations obtained with ESPaDOnS at the Canada-France-Hawaii Telescope. Our observations reveal detectable, often complex, Stokes V Zeeman signatures in Least-Squares Deconvolved mean line profiles in a significant fraction of the observed sample of ~30 stars.

I will review our recent analysis of the magnetic properties of the O9IV star HD 57682, using spectropolarimetric observations obtained with ESPaDOnS at the Canada-France-Hawaii telescope within the context of the Magnetism in Massive Stars (MiMeS) Large Program. I discuss our most recent determination of the rotational period from longitudinal magnetic field measurements and Hα variability - the latter obtained from over a decade's worth of professional and amateur spectroscopic observations. Lastly, I will report on our investigation of the magnetic field geometry and the effects of the field on the circumstellar environment.

We discuss the recent detection of a strong, organized magnetic field in the bright, broad-line B2V star, HD 142184, using the ESPaDOnS spectropolarimeter on the CFHT as part of the Magnetism in Massive Stars (MiMeS) survey. We find a rotational period of 0.50833 days, making it the fastest-rotating, non-degenerate magnetic star ever detected. Like the previous rapid-rotation record holder HR 7355 (also discovered by MiMeS: Oksala et al. 2010, Rivinius et al. 2010), this star shows emission line variability that is diagnostic of a structured magnetosphere.

The ultraviolet stellar wind lines of the photometrically periodic variable early B-type star σ Lupi were found to behave very similarly to what has been observed in known magnetic B stars, although no periodicity could be determined. AAT spectropolarimetric measurements with SEMPOL were obtained. We detected a longitudinal magnetic field with varying strength and amplitude of about 100 G with error bars of typically 20 G. This type of variability supports an oblique magnetic rotator model. We fold the equivalent width of the 4 usable UV spectra in phase with the well-known photometric period of 3.019 days, which we identify with the rotation period of the star. The magnetic field variations are consistent with this period. Additional observations with ESPaDOnS attached to the CFHT strongly confirmed this discovery, and allowed to determine a precise magnetic period. Like in the other magnetic B stars the wind emission likely originates in the magnetic equatorial plane, with maximum emission occurring when a magnetic pole points towards the Earth. The 3.0182 d magnetic rotation period is consistent with the photometric period, with maximum light corresponding to maximum magnetic field. No helium or other chemical peculiarity is known for this object.

We present Rigid Field Hydrodynamic simulations of the magnetosphere of σ Ori E. We find that the X-ray emission from the star's magnetically confined wind shocks is very sensitive to the assumed mass-loss rate. To compare the simulations against the measured X-ray emission, we first disentangle the star from its recently discovered late-type companion using Chandra HRC-I observations. This then allows us to place an upper limit on the mass-loss rate of the primary, which we find to be significantly smaller than previously imagined.