2021A&A...647A.139L


Query : 2021A&A...647A.139L

2021A&A...647A.139L - Astronomy and Astrophysics, volume 647A, 139-139 (2021/3-1)

Orbital solutions derived from radial velocities and time delays for four Kepler systems with A/F-type (candidate) hybrid pulsators.

LAMPENS P., VERMEYLEN L., FREMAT Y., SODOR A., SKARKA M., SAMADI-GHADIM A., BOGNAR Z., LEHMANN H., DE CAT P., GOSWAMI A. and DUMORTIER L.

Abstract (from CDS):


Context. The presence of A/F-type Kepler hybrid stars extending across the entirety of the δ Scuti - γ Doradus instability strips and beyond remains largely unexplained. In order to better understand these particular stars, we performed a multi-epoch spectroscopic study of a sample of 49 candidate A/F-type hybrid stars and one cool(er) hybrid object detected by the Kepler mission. We determined a lower limit of 27% for the multiplicity fraction. For six spectroscopic systems, we also reported long-term variations in the time delays (TDs). For four systems, the TD variations are fully coherent with those of the radial velocities (RVs ) and can be attributed to orbital motion.
Aims. We aim to improve the orbital solutions for those spectroscopic systems with long orbital periods (order of 4-6 years) among the Kepler hybrid stars that we continued to observe.
Methods. The orbits are computed based on a simultaneous modelling of the RVs obtained with high-resolution spectrographs and the photometric TDs derived from time-dependent frequency analyses of the Kepler light curves.
Results. We refined the orbital solutions of four spectroscopic systems with A/F-type Kepler hybrid component stars: KIC 4480321, 5219533, 8975515, and KIC 9775454. Simultaneous modelling of both data types analysed together enabled us to improve the orbital solutions (all), obtain more robust and accurate information on the mass ratio (some for the first time), and identify the component with the short-period δ Sct-type pulsations (all). The information gained is maximized when one of the components, generally the one exhibiting the δ Sct-type pulsations, is a fast rotator. In several cases, we were also able to derive new constraints for the minimum component masses. From a search for regular frequency patterns in the high-frequency regime of the Fourier transforms of each system, we found no evidence of tidal splitting among the triple systems with close (inner) companions. However, some systems exhibit frequency spacings that can be explained by the mechanism of rotational splitting.

Abstract Copyright: © ESO 2021

Journal keyword(s): binaries: spectroscopic - stars: variables: delta Scuti - asteroseismology - techniques: radial velocities - techniques: photometric

Simbad objects: 9

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Number of rows : 9
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 HD 177876 EB* 19 04 04.6072024824 +48 52 00.102075096   7.80 7.68     A3IV-n 47 0
2 2MASS J19090308+3915360 EB* 19 09 03.0843912720 +39 15 36.101633688           A9V 35 0
3 KOI-6655 EB* 19 34 14.0268911664 +41 23 43.302641964           ~ 21 0
4 HD 185115 dS* 19 35 32.0032141248 +46 35 22.318231128   8.516 8.19     F1Vs 28 0
5 HD 225479 dS* 19 42 38.3938128600 +39 33 40.365258696   10.56 10.27     A9Vwkmet(A5) 24 0
6 HD 188538 dS* 19 53 45.5746985808 +45 13 09.285444840   9.82 9.48     A7IV 21 0
7 HD 226766 dS* 19 57 09.9096799008 +40 22 50.570615424   9.51 9.28     kA1hA5mA7Sr 24 0
8 HD 189178 SB* 19 57 13.8676056936 +40 22 04.173175488   5.352 5.455     B5V 73 0
9 V* U Gru SB* 21 31 48.7735728624 -45 02 42.338331492   11.46 11.22 11.34   A5 35 1

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