J/ApJ/459/278ivo://CDS.VizieR/J/ApJ/459/278doi:10.26093/cds/vizier.14590278CDSMatthews J.M.Wehlau W.H.Rice J.Walker G.A.H.1997-12-09T19:58:36Z1997-12-09T20:58:27ZCDS support team

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

cds-question@unistra.frap-starsphotometryinfrared-photometryWe demonstrate a new approach for probing the atmospheres of selected chemically peculiar magnetic stars. Using the Cerro Tololo Inter-American Observatory (CTIO) 1.0 and 1.5m telescopes simultaneously on two nights in 1991, we obtained optical and infrared high-speed photometry of the rapidly oscillating Ap (roAp) star HR 3831 (=HD 83368), which pulsates with a period of ~11.8 minutes. Oscillation amplitudes (or upper limits) in each of eight bandpasses were measured by Fourier analysis, revealing the very steep decline in amplitude with increasing wavelength characteristic of roAp stars. Matthews and coworkers have shown that this can be explained by the wavelength dependence of limb darkening and its filtering effect on the integrated amplitude of an (l,m)=(1,0) nonradial pulsation mode. Since the eigenfrequency spectrum of HR 3831 is dominated by just such a dipole mode, it is possible to infer limb-darkening coefficients beta(lambda) for its atmosphere from our amplitude measurements. These coefficients are used to derive a source function through the Eddington-Barber relation, which leads to a relation for temperature versus optical depth in the stellar photosphere. Our results show that the T-Tau(5000) curve is much steeper for HR 3831 than for the Sun (at least at the rotational phase when the star's magnetic pole dominates the visible hemisphere). We also calculate the gradient dT/dtau as a function of wavelength to compare with the curve expected for H- continuous opacity. This type of diagnostic may become a useful tool for checking the predictions of diffusion theory.1996ApJ...459..278Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/459/278CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/459/278https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/459/278http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/459/278https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/459/278https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/459/278http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/459/278GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapInfrareddefaultJ/ApJ/459/278/hr3831bDifferential photometry, b bandpassrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2448000Heliocentric Julian Date - 2448000dtime.epochdoubledMagDifferential magnitude normalized to the meanmagphot.mag;arith.difffloatJ/ApJ/459/278/hr3831vDifferential photometry, v bandpassrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2448000Heliocentric Julian Date - 2448000dtime.epochdoubledMagDifferential magnitude normalized to the meanmagphot.mag;arith.difffloatJ/ApJ/459/278/hr3831yDifferential photometry, y bandpassrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2448000Heliocentric Julian Date - 2448000dtime.epochdoubledMagDifferential magnitude normalized to the meanmagphot.mag;arith.difffloatJ/ApJ/459/278/hr3831rDifferential photometry, R bandpassrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2448000Heliocentric Julian Date - 2448000dtime.epochdoubledMagDifferential magnitude normalized to the meanmagphot.mag;arith.difffloatJ/ApJ/459/278/hr3831iDifferential photometry, I bandpassrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2448000Heliocentric Julian Date - 2448000dtime.epochdoubledMagDifferential magnitude normalized to the meanmagphot.mag;arith.difffloatJ/ApJ/459/278/hr3831jDifferential photometry, J bandpassrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2448000Heliocentric Julian Date - 2448000dtime.epochdoubledMagDifferential magnitude normalized to the meanmagphot.mag;arith.difffloatJ/ApJ/459/278/hr3831hDifferential photometry, H bandpassrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2448000Heliocentric Julian Date - 2448000dtime.epochdoubledMagDifferential magnitude normalized to the meanmagphot.mag;arith.difffloatJ/ApJ/459/278/hr3831kDifferential photometry, K bandpassrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-2448000Heliocentric Julian Date - 2448000dtime.epochdoubledMagDifferential magnitude normalized to the meanmagphot.mag;arith.difffloat