J/A+A/335/973ivo://CDS.VizieR/J/A+A/335/973doi:10.26093/cds/vizier.33350973CDSWade G.A.Hill G.M.Adelman S.J.Manset N.Bastien P.1998-08-05T19:46:16Z1998-08-05T19:46:12ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frpeculiar-variable-starsbe-starsvisible-astronomymedium-band-photometryWe present new longitudinal magnetic field and Stroemgren photometric measurements of the Bp star 84 UMa. From these data we determine a new rotational period P_rot_=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_{deg}, {beta}=48^+17^_-29_{deg}, and B_d_=1620^+1270^_-30_G. 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.1998A&A...335..973Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/335/973CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/314/491 : HD 59435 radial velocity + Geneva photometry (Wade+ 1996)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/335/973https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/335/973http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/335/973https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/335/973https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/335/973http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/335/973GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/335/973/table2Photometry of 84 UMarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJDHeliocentric Julian Datedtime.epochdoubleu(v-c)variable-comparison (v-c) u magnitudemagphot.mag;arith.difffloatu(ch-c)check-comparison (ch-c) u magnitudemagphot.mag;arith.difffloatv(v-c)variable-comparison (v-c) v magnitudemagphot.mag;arith.difffloatv(ch-c)check-comparison (ch-c) v magnitudemagphot.mag;arith.difffloatb(v-c)variable-comparison (v-c) b magnitudemagphot.mag;arith.difffloatb(ch-c)check-comparison (ch-c) b magnitudemagphot.mag;arith.difffloaty(v-c)variable-comparison (v-c) y magnitudemagphot.mag;arith.difffloaty(ch-c)check-comparison (ch-c) y magnitudemagphot.mag;arith.difffloat