Non-radial pulsation, rotation and outburst in the
Be star
Orionis
from the MuSiCoS 1998 campaign
C. Neiner1,2,
A.-M. Hubert1,
M. Floquet1,
S. Jankov3,4,
H.F. Henrichs2,
B. Foing5,
J. Oliveira5,6,
S. Orlando5,7,
J. Abbott8,9,
I.K. Baldry10,
T.R. Bedding10,
J. Cami2,
H. Cao11,
C. Catala12,
K.P. Cheng13,
A. Domiciano de Souza Jr14,3,
E. Janot-Pacheco1,14,
J.X. Hao11,
L. Kaper2,
A. Kaufer15,
N.V. Leister14,
J.E. Neff16,
S.J. O'Toole10,
D. Schäfer18,
S.J. Smartt19,20,
O. Stahl18,
J. Telting8,21,
S. Tubbesing18,
and J. Zorec22
1 GEPI/FRE 2459,
Observatoire de Paris-Meudon, France
2 Sterrenkundig Instituut Anton Pannekoek, Universiteit van Amsterdam, Netherlands
3 FRESNEL/UMR 6528 du CNRS, Observatoire de la Côte d'Azur (OCA), France
4 Astronomical Observatory Beograd, Yugoslavia
5 ESA Solar System Division, Space Science Department, ESTEC, Netherlands
6 Department of Physics, Keele University, Staffordshire, United Kingdom
7 Osservatorio Astronomico di Palermo "G.S. Vaiana", Italy
8 Isaac Newton Group (ING), La Palma Island, Spain
9 Department of Physics & Astronomy, University College London, United Kingdom
10 School of Physics, University of Sydney 2006, Australia
11 Beijing Astronomical Observatory, China
12 LESIA, Observatoire de Paris-Meudon, France
13 California State University, Fullerton, CA, USA
14 Instituto Astronomico e Geofisico, Universidade de Sao Paulo, Brazil
15 European Southern Observatory, Chile
16 College of Charleston, Charleston, SC, USA
17 Natural Sciences and Mathematics, West Liberty State College, USA
18 Landessternwarte Heidelberg-Königstuhl, Germany
19 Institute of Astronomy, University of Cambridge, England
20 Marshall Space Flight Center, Huntsville, AL, USA
21 Nordic Optical Telscope (NOT), La Palma Island, Spain
22 Institut d'Astrophysique de Paris (IAP), France
Ori
(HD 37490, HR 1934) is a Be star known to have
presented variations. In order to investigate the nature and origin
of its short-term and mid-term variability, a study is performed of
several spectral lines
(H ,
H ,
HeI 4471,
4713, 4921, 5876, 6678,
CII 4267, 6578, 6583,
MgII 4481,
SiIII 4553 and
SiII 6347),
based on 249 high
signal-to-noise high-resolution spectra taken with 8 telescopes over
22 consecutive nights during the MuSiCoS (Multi SIte COntinuous
Spectroscopy) campaign in November-December 1998. The stellar
parameters are revisited and the projected rotational velocity
(v sin i = 179 km s-1)
is redetermined using several
methods. With the MuSiCoS 98 dataset, a time series analysis of
line-profile variations (LPVs) is performed using the Restricted Local
Cleanest (RLC) algorithm and a least squares method. The behaviour of
the velocity of the centroid of the lines, the equivalent widths and
the apparent v sin i for several lines, as well as
Violet and Red
components of photospheric lines affected by emission (red
HeI lines,
SiII 6347,
CII 6578, 6583)
are analyzed. The non-radial pulsation (NRP) model is examined using
phase diagrams and the Fourier-Doppler Imaging (FDI) method. The LPVs
are consistent with a NRP mode with l = 2 or 3,
|m| = 2 with
frequency 1.03 c d-1. It is shown that an emission
line outburst
occurred in the middle of the campaign. Two scenarios are proposed to
explain the behaviour of a dense cloud, temporarily orbiting around
the star with a frequency 0.46 c d-1, in relation to
the outburst.
Orionis
from the MuSiCoS 1998 campaign
Ori
(HD 37490, HR 1934) is a Be star known to have
presented variations. In order to investigate the nature and origin
of its short-term and mid-term variability, a study is performed of
several spectral lines
(H 
,
H 
,
HeI 4471,
4713, 4921, 5876, 6678,
CII 4267, 6578, 6583,
MgII 4481,
SiIII 4553 and
SiII 6347),
based on 249 high
signal-to-noise high-resolution spectra taken with 8 telescopes over
22 consecutive nights during the MuSiCoS (Multi SIte COntinuous
Spectroscopy) campaign in November-December 1998. The stellar
parameters are revisited and the projected rotational velocity
(v sin i = 179 km s-1)
is redetermined using several
methods. With the MuSiCoS 98 dataset, a time series analysis of
line-profile variations (LPVs) is performed using the Restricted Local
Cleanest (RLC) algorithm and a least squares method. The behaviour of
the velocity of the centroid of the lines, the equivalent widths and
the apparent v sin i for several lines, as well as
Violet and Red
components of photospheric lines affected by emission (red
HeI lines,
SiII 6347,
CII 6578, 6583)
are analyzed. The non-radial pulsation (NRP) model is examined using
phase diagrams and the Fourier-Doppler Imaging (FDI) method. The LPVs
are consistent with a NRP mode with l = 2 or 3,
|m| = 2 with
frequency 1.03 c d-1. It is shown that an emission
line outburst
occurred in the middle of the campaign. Two scenarios are proposed to
explain the behaviour of a dense cloud, temporarily orbiting around
the star with a frequency 0.46 c d-1, in relation to
the outburst.