J/A+A/335/973 84 UMa ubvy photometry (Wade+ 1998)
Magnetic field models for A and B stars.
V. The magnetic field and photometric variations of 84 UMa
Wade G.A., Hill G.M., Adelman S.J., Manset N., Bastien P.
<Astron. Astrophys. 335, 973 (1998)>
=1998A&A...335..973W 1998A&A...335..973W (SIMBAD/NED BibCode)
ADC_Keywords: Stars, peculiar ; Stars, Be ; Stars, Bp ; Photometry, uvby
Keywords: stars: chemically peculiar - stars: individual: 84 UMa -
Stars: magnetic fields - polarisation
Abstract:
We present new longitudinal magnetic field and Stroemgren photometric
measurements of the Bp star 84 UMa. From these data we determine a new
rotational period Prot=1.38576±0.00080d, which is inconsistent
with previously published values. The magnetic measurements indicate
the presence of a weak, dominantly dipolar magnetic field in the
photosphere of 84 UMa. We employ a new value of the rotational axis
inclination in conjunction with the magnetic data in order to
constrain the magnetic field geometry. We derive the following dipole
oblique rotator parameters: i=59+17-9°,
β=48+17-29°, and Bd=1620+1270-30G. A precise value
of the radius (which we calculate in conjunction with the inclination
using the Hipparcos parallax) allows us to locate 84 UMa on the
radius-effective temperature plane. Using theoretical evolutionary
tracks (Schaller et al., 1992, Cat. J/A+AS/96/269), we obtain values
for the mass, age and surface gravity. These results place 84 UMa
quite close to the ZAMS, a result inconsistent with the suggestion by
Hubrig & Mathys (1994AN....315..343H 1994AN....315..343H) that the magnetic Ap stars may
be near the end of their main sequence life.
Objects:
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RA (2000) DE Designation(s)
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13 46 35.7 +54 25 58 84 UMa = HD 120198
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 68 73 Photometry of 84 UMa
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See also:
J/A+A/314/491 : HD 59435 radial velocity + Geneva photometry (Wade+ 1996)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Heliocentric Julian Date
14- 19 F6.3 mag u(v-c) variable-comparison (v-c) u magnitude
21- 26 F6.3 mag u(ch-c) check-comparison (ch-c) u magnitude
28- 33 F6.3 mag v(v-c) variable-comparison (v-c) v magnitude
35- 40 F6.3 mag v(ch-c) check-comparison (ch-c) v magnitude
42- 47 F6.3 mag b(v-c) variable-comparison (v-c) b magnitude
49- 54 F6.3 mag b(ch-c) check-comparison (ch-c) b magnitude
56- 61 F6.3 mag y(v-c) variable-comparison (v-c) y magnitude
63- 68 F6.3 mag y(ch-c) check-comparison (ch-c) y magnitude
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Average and standard deviation:
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u v b y
v-c ch-c v-c ch-c v-c ch-c v-c ch-c
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average -0.158 -0.391 -0.020 -0.380 -0.044 -0.340 0.002 -0.329
std. dev. 0.011 0.007 0.007 0.005 0.008 0.005 0.005 0.005
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Acknowledgements: Saul J. Adelman
References:
Wade et al., HD 115708 1996A&A...307..500W 1996A&A...307..500W
Wade et al., HD 192678 1996A&A...313..209W 1996A&A...313..209W
Wade et al., HD 184927 1997A&A...320..172W 1997A&A...320..172W
Wade et al., HD 200311 1997MNRAS.292..748W 1997MNRAS.292..748W
(End) Patricia Bauer [CDS] 22-Apr-1998