Kavli Affiliate: Huawei Zhang
| First 5 Authors: Fangfei Shi, Huawei Zhang, Swetlana Hubrig, Silva Jarvinen, Huiling Chen
| Summary:
KIC 10685175 is a roAp star whose polar magnetic field is predicted to be 6
kG through a non-adiabatic axisymmetric pulsation theoretical model. In this
work, we aim to measure the magnetic field strength of KIC 10685175 using
high-resolution spectropolarimetric observations, and compare it with the one
predicted by the theoretical model. From the study of two high-resolution
unpolarized spectra, we obtained [$T_{rm eff}$, $log g$, [Fe/H],
[$alpha$/Fe], $V_{mic}$]=[8250 $pm$ 200,K, 4.4 $pm$ 0.1, -0.4 $pm$ 0.2,
0.16 $pm$ 0.1, 1.73 $pm$ 0.2,km~s$^{-1}$]. Although the Fe absorption lines
appear relatively weak in comparison to typical Ap stars with similar $T_{rm
eff}$, the lines belonging to rare earth elements (Eu and Nd) are stronger than
that in chemically normal stars, indicating the peculiar nature of
KIC~10685175. The mean longitudinal magnetic field $langle B_ell
rangle=-226pm39$,G has been measured in the polarized spectrum, but
magnetically split lines were not detected. No significant line profile
variability was evident in our spectra. Also the longitudinal magnetic field
strengths measured using line masks constructed for different elements have
been rather similar. Due to a poor rotation phase coverage of our data,
additional spectroscopic and polarimetric observations are needed to allow us
to conclude on the inhomogeneous element distribution over the stellar surface.
The estimated polar magnetic field is $4.8 pm 0.8$,kG, which is consistent
with the predicted polar magnetic field strength of about 6,kG within
3$sigma$. This work therefore provides support for the pulsation theoretical
model.
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