TY - JOUR
T1 - KIC 1718290
T2 - A helium-rich V1093-her-like pulsator on the blue horizontal branch
AU - Østensen, R. H.
AU - Degroote, P.
AU - Telting, J. H.
AU - Vos, J.
AU - Aerts, C.
AU - Jeffery, C. S.
AU - Green, E. M.
AU - Reed, M. D.
AU - Heber, U.
PY - 2012/7/1
Y1 - 2012/7/1
N2 - We introduce the first g-mode pulsator found to reside on the classical blue horizontal branch. One year of Kepler observations of KIC1718290 reveals a rich spectrum of low-amplitude modes with periods between 1 and 12 hr, most of which follow a regular spacing of 276.3s. This mode structure strongly resembles that of the V1093Her pulsators, with only a slight shift toward longer periods. Our spectroscopy, however, reveals KIC1718290 to be quite distinct from the sdB stars that show V1093Her pulsations, which all have surface gravities higher than log g= 5.1 and helium abundances depleted by at least an order of magnitude relative to the solar composition. We find that KIC1718290 has T eff= 22,100K, log g= 4.72, and a super-solar helium abundance (log N He/N H= -0.45). This places it well above the extreme horizontal branch, rather on the very blue end of the classical horizontal branch, where shell hydrogen burning is present. We conclude that KIC1718290 must have suffered extreme mass loss during its first giant stage, but not sufficient to reach the extreme horizontal branch.
AB - We introduce the first g-mode pulsator found to reside on the classical blue horizontal branch. One year of Kepler observations of KIC1718290 reveals a rich spectrum of low-amplitude modes with periods between 1 and 12 hr, most of which follow a regular spacing of 276.3s. This mode structure strongly resembles that of the V1093Her pulsators, with only a slight shift toward longer periods. Our spectroscopy, however, reveals KIC1718290 to be quite distinct from the sdB stars that show V1093Her pulsations, which all have surface gravities higher than log g= 5.1 and helium abundances depleted by at least an order of magnitude relative to the solar composition. We find that KIC1718290 has T eff= 22,100K, log g= 4.72, and a super-solar helium abundance (log N He/N H= -0.45). This places it well above the extreme horizontal branch, rather on the very blue end of the classical horizontal branch, where shell hydrogen burning is present. We conclude that KIC1718290 must have suffered extreme mass loss during its first giant stage, but not sufficient to reach the extreme horizontal branch.
KW - stars: horizontal-branch
KW - stars: individual (KIC 1718290)
KW - stars: oscillations
KW - stars: variables: general
KW - subdwarfs
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U2 - 10.1088/2041-8205/753/1/L17
DO - 10.1088/2041-8205/753/1/L17
M3 - Article
AN - SCOPUS:84862684326
SN - 2041-8205
VL - 753
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - L17
ER -