J/A+A/409/275 Rotation and magnetic field in omega Ori (Neiner+, 2003)
Rotation and magnetic field in the Be star omega Orionis
Neiner C., Hubert A.M., Fremat Y., Floquet M., Jankov S., Preuss O.,
Henrichs H.F., Zorec J.
<Astron. Astrophys. 409, 275 (2003)>
=2003A&A...409..275N 2003A&A...409..275N
ADC_Keywords: Stars, Be ; Magnetic fields
Keywords: stars: magnetic fields - stars: oscillations -
stars: winds, outflows - stars: individual: omega Ori
Abstract:
Omega Ori is a B2IIIe star for which rotational modulation and
non-radial pulsations (NRP) have been recently investigated from two
independent observational campaigns in 1998 and 1999. Putting the data
of these 2 campaigns together, and adding data obtained in 2001, we
search for multiperiodicity in the line profile variations and
evidence for outbursts. From new spectropolarimetric data obtained at
the Telescope Bernard Lyot (TBL, Pic du Midi, France) in 2001 we also
measure the Stokes V parameter in the polarised light. We find
evidence for the presence of a weak magnetic field in Omega Ori
sinusoidally varying with a period of 1.29d. The equivalent widths
(EW) of the wind sensitive UV resonance lines also show a variation
with the same period, which we identify as the rotational period of
the star. We propose an oblique rotator model and derive
Bpol=530±230G to explain the observations. Moreover, we carry out
an abundance analysis and find the star to be N-enriched, a property
which is shared with other magnetic stars. We propose Omega Ori as the
first known classical Be star hosting a magnetic field.
Description:
Spectra were obtained during the MuSiCoS campaign from November 23 to
December 15 in 1998. This campaign used 8 telescopes around the world
simultaneously to obtain continuous spectroscopy (data described in
Neimer et al., 2002A&A...388..899N 2002A&A...388..899N).
Spectra were also obtained from November 17 to December 7 in 1999
(data described in Balona et al., 2001MNRAS.327.1288B 2001MNRAS.327.1288B).
Finally, spectropolarimetric data were obtained at TBL (Pic du Midi,
France) from December 19 to 24 in 2001 with the spectropolarimeter
Musicos.
Objects:
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RA (2000) DE Designation(s)
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05 39 11 +04 07.3 omega Ori = HD 37490
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table7.dat 39 36 Longitudinal magnetic field measurements
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See also:
J/A+A/368/912 : Be stars polarization and rotational velocities (Yudin, 2001)
J/A+AS/111/399 : Polarization variability in Herbig Ae/Be stars (Jain+, 1995)
Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Nexp Number of the exposure
4- 14 F11.3 d HJD Heliocentric Julian Date at mid-exposure
16- 21 F6.4 --- Phase [0/1[ Phase with f=0.78c/d and HJD0=2452265.1
23- 26 I4 10-7T B Longitudinal field (in Gauss)
28- 30 I3 10-7T e_B rms uncertainty on B
32- 35 I4 10-7T N Null polarisation (1)
37- 39 I3 10-7T e_N rms uncertainty on N
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Note (1): The null polarisation gives an indication of the pollution by
non-stellar effects and should be zero for a perfect measurement.
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Acknowledgements: Coralie Neiner
(End) Patricia Bauer [CDS] 18-Jul-2003