Query : 2020A&A...638A..57S

2020A&A...638A..57S - Astronomy and Astrophysics, volume 638A, 57-57 (2020/6-1)

KIC 8975515: A fast-rotating (γ Dor - δ Sct) hybrid star with Rossby modes and a slower δ Sct companion in a long-period orbit.


Abstract (from CDS):

Aims. KIC 8975515 is a double-lined spectroscopic binary system with hybrid nature. Regular monitoring with the echelle spectrographHERMES show that both components have matching atmospheric properties (Teff∼7400K), and that one of them is a fast rotator (vsini=162 versus 32km/s). Our aim is to study the Kepler light curve in order to determine the frequencies of the pulsations, to search for regular spacing patterns in the Fourier spectrum, if any, and to discuss their origin in the context of binarity and fast rotation.
Methods. In this paper, we study the properties of the stellar pulsations based on a careful analysis of the Fourier spectrum. This was done by performing repeated frequency-search analyses with successive prewhitenings of all the significant frequencies detected in the spectrum. Moreover, we searched for regular period spacing among the g modes as well as frequency splitting among the g and p modes in frequency.
Results. In the low-frequency regime, one series of prograde g modes and four series of retrograde r modes, were detected. The r modes are well-distributed with respect to the harmonics of the rotational frequency of the fast-rotating star frot=1.647d–1. The dominant g mode is f2=2.37d–1. The strongest p mode is f1=13.97d–1. We identified two multiplets of regularly split p modes with the mean values of 0.42d–1 and 1.65d–1. In addition, we also identified a few incidences of mode coupling (between f1 and a g or r mode).
Conclusions. We detected five series of retrograde r and prograde g modes as well as two multiplets of p modes with rotational frequency splitttings related to both components of KIC 8975515. We identified the fast-rotating component as a hybrid pulsator with r modes, and the slowly-rotating component as a δ Sct pulsator.

Abstract Copyright: © ESO 2020

Journal keyword(s): techniques: photometric - techniques: spectroscopic - binaries: spectroscopic - stars: variables: d Scuti - asteroseismology - stars: rotation

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 ASAS J190333+3941.0 EB* 19 03 32.7241267608 +39 41 00.370851648   10.95 10.83   10.582 A3V 64 0
2 HD 181469 SB* 19 18 58.21759 +39 16 01.7913   8.336 8.021 8.65   F1Vwkmet(A9) 64 0
3 TYC 3139-826-1 dS* 19 32 25.5830766816 +40 54 03.072173940   11.61 11.53     F0III-IV 16 0
4 KOI-6655 EB* 19 34 14.0268911664 +41 23 43.302641964           ~ 19 0
5 KOI-7196 EB* 19 35 04.8399531070 +46 14 11.701237018   12.50 13.23   11.812 kA2hA5mA8Si 42 0
6 TYC 3560-2433-1 dS* 19 36 27.3036735096 +47 05 02.149341756   12.40 11.65     F6II 55 0
7 HD 188538 dS* 19 53 45.5746985808 +45 13 09.285444840   9.82 9.48     A7IV 20 0

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