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Revel, France

Miroshnichenko A.S.,University of North Carolina at Greensboro | Pasechnik A.V.,University of Turku | Manset N.,CFHT Corporation | Carciofi A.C.,University of Sao Paulo | And 19 more authors.
Astrophysical Journal | Year: 2013

We describe the results of the world-wide observing campaign of the highly eccentric Be binary system δ Scorpii 2011 periastron passage which involved professional and amateur astronomers. Our spectroscopic observations provided a precise measurement of the system orbital period at 10.8092 ± 0.0005 yr. Fitting of the He II 4686 Å line radial velocity curve determined the periastron passage time on 2011 July 3, UT 9:20 with a 0.9-day uncertainty. Both these results are in a very good agreement with recent findings from interferometry. We also derived new evolutionary masses of the binary components (13 and 8.2 M⊙) and a new distance of 136 pc from the Sun, consistent with the HIPPARCOS parallax. The radial velocity and profile variations observed in the Hα line near the 2011 periastron reflected the interaction of the secondary component and the circumstellar disk around the primary component. Using these data, we estimated a disk radius of 150 R⊙. Our analysis of the radial velocity variations measured during the periastron passage time in 2000 and 2011 along with those measured during the 20th century, the high eccentricity of the system, and the presence of a bow shock-like structure around it suggest that δ Sco might be a runaway triple system. The third component should be external to the known binary and move on an elliptical orbit that is tilted by at least 40° with respect to the binary orbital plane for such a system to be stable and responsible for the observed long-term radial velocity variations. © 2013. The American Astronomical Society. All rights reserved. Source

Neiner C.,University Paris Diderot | Alecian E.,University Paris Diderot | Briquet M.,University Paris Diderot | Briquet M.,Catholic University of Leuven | And 4 more authors.
Astronomy and Astrophysics | Year: 2012

Aims. Following the indirect detection of a magnetic field in the β Cephei star V2052 Oph by Neiner and collaborators in 2003 with the Musicos spectropolarimeter, we remeasured the magnetic field of this star to attempt to directly confirm the detection of a magnetic field and study its configuration in greater detail. Methods. We used the Narval spectropolarimeter installed at TBL (Pic du Midi, France), which is about 20 times more efficient than the Musicos spectropolarimeter. We applied the least-squares deconvolution (LSD) technique to various groups of lines to measure the circular polarisation of the light coming from V2052 Oph. We synthesized the measured Stokes V profiles with a centred and off-centred dipole model. Results. For the first time, we clearly detect the Zeeman signature in the Stokes V profiles of V2052 Oph and thus directly prove the presence of a magnetic field in this star. The modulation with the rotation period is also confirmed and reflects an oblique dipole field. Thanks to the small error bars on the measurements, we are able to study the behaviour of different groups of lines and the centring of the dipole in the star. We find that the dipole is most likely off-centred along the magnetic axis and that He spots are present at the surface next to the magnetic axis. Conclusions. We conclude that V2052 Oph is a magnetic He-strong β Cep star, with a dipole field, probably off-centred, with Bpol ∼ 400 G and He patches close to the magnetic poles. © ESO, 2012. Source

De Batz B.,LESIA | Neiner C.,LESIA | Floquet M.,GEPI | Cochard F.,Shelyak Instruments
Proceedings of the International Astronomical Union | Year: 2010

We present the status of the BeSS database, which contains a catalogue of all known classical Be stars and a large collection of their spectra obtained at any wavelength, any epoch, and from various sources, from amateur astronomer spectra to professional high-resolution high signal-to-noise echelle spectra. Efficient data retrieval in such a heterogeneous data collection is possible with a wide range of selection criteria thanks to their storage in the fits format and via a web interface (http://basebe.obspm.fr) as well as via the Virtual Observatory. BeSS already contains over 49000 spectra and has allowed the detection of several outbursts. © International Astronomical Union 2011. Source

Cochard F.,Shelyak Instruments | Desnoux V.,Amateur Ring for Astronomical Spectroscopy | Buil C.,Amateur Ring for Astronomical Spectroscopy
Proceedings of the International Astronomical Union | Year: 2010

Since 2003, the amateur astronomical community has decided, in collaboration with the Paris-Meudon Observatory, to coordinate their observations to get the best spectral survey of Be stars as possible. A database for amateur and professional Be star spectra, BeSS, has been created. Spectrographs (up to R=20000) and software tools have been developed for amateurs. Among them, ArasBeam is a web-based tool designed to organize amateur Be spectral observations. A very simple color coding indicates to any observer which stars must be observed on the following night to get the best possible survey of Be stars. So far, more than 11000 amateur spectra have been collected in BeSS. About all bright Be stars (up to magnitude 8) listed in BeSS and visible from the Northern hemisphere have been observed at least one time. In addition, 6 outbursts have been detected by amateurs in the last 2 years. © International Astronomical Union 2011. Source

Neiner C.,University Paris Diderot | Grunhut J.H.,Queens University | Grunhut J.H.,Royal Military College of Canada | Petit V.,West Chester University | And 8 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

One hundred and twenty-five new high-precision spectropolarimetric observations have been obtained with ESPaDOnS (Eschelle Spectro-Polarimetric Device for the Observation of Stars) at the Canada-France-Hawaii Telescope and Narval at Télescope Bernard Lyot to investigate the magnetic properties of the classical Be star ω Ori. No Stokes V signatures are detected in our polarimetric data. Measurements of the longitudinal magnetic field, with a median error bar of 30G, and direct modelling of the mean least-squares deconvolved Stokes V profiles yield no evidence for a dipole magnetic field with polar surface strength greater than ∼80G. We are therefore unable to confirm the presence of the magnetic field previously reported by Neiner et al. However, our spectroscopic data reveal the presence of periodic emission variability in H and He lines analogous to that reported by Neiner et al., considered as evidence of magnetically confined circumstellar plasma clouds. We revisit this hypothesis in light of the new magnetic analysis. Calculation of the magnetospheric Kepler radius R K and confinement parameter η * indicates that a surface dipole magnetic field with a polar strength larger than 63G is sufficient to form of a centrifugally supported magnetosphere around ω Ori. Our data are not sufficiently sensitive to detect fields of this magnitude; we are therefore unable to confirm or falsify the magnetic cloud hypothesis. Based on our results, we examine three possible scenarios that could potentially explain the behaviour of ω Ori: (1) that no significant magnetic field is (or was) present in ω Ori, and that the observed phenomena have their origin in another mechanism or mechanisms than corotating clouds. We are, however, unable to identify one; (2) that ω Ori hosts an intermittent magnetic field produced by dynamo processes; however, no such process has been found so far to work in massive stars and especially to produce a dipolar field; and (3) that ω Ori hosts a stable, organized (fossil) magnetic field that is responsible for the observed phenomena, but with a strength that is below our current detection threshold. Of these three scenarios, we consider the second one (dynamo process) as highly unlikely, whereas the other two should be falsifiable with intense monitoring. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS. Source

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