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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 (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) that the magnetic Ap stars may be near the end of their main sequence life. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 13 46 35.7 +54 25 58 84 UMa = HD 120198 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 68 73 Photometry of 84 UMa
See also: J/A+A/314/491 : HD 59435 radial velocity + Geneva photometry (Wade+ 1996) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
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
Average and standard deviation: -------------------------------------------------------------------------- u v b y v-c ch-c v-c ch-c v-c ch-c v-c ch-c -------------------------------------------------------------------------- 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 Acknowledgements: Saul J. Adelman References: Wade et al., HD 115708 1996A&A...307..500W Wade et al., HD 192678 1996A&A...313..209W Wade et al., HD 184927 1997A&A...320..172W Wade et al., HD 200311 1997MNRAS.292..748W
(End) Patricia Bauer [CDS] 22-Apr-1998
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