TY  - JOUR
A1  - Vos, Joris
A1  - Vuckovic, Maja
A1  - Chen, Xuefei
A1  - Han, Zhanwen
A1  - Boudreaux, Thomas
A1  - Barlow, Brad N.
A1  - Ostensen, Roy
A1  - Németh, Péter
T1  - The orbital period-mass ratio relation of wide sdB plus MS binaries and its application to the stability of RLOF
JF  - Monthly notices of the Royal Astronomical Society
N2  - Wide binaries with hot subdwarf-B (sdB) primaries and main sequence companions are thought to form only through stable Roche-lobe overflow (RLOF) of the sdB progenitor near the tip of the red giant branch (RGB). We present the orbital parameters of 11 new long-period composite sdB binaries based on spectroscopic observations obtained with the UVES, FEROS, and CHIRON spectrographs. Using all wide sdB binaries with known orbital parameters, 23 systems, the observed period distribution is found to match very well with theoretical predictions. A second result is the strong correlation between the orbital period (P) and the mass ratio (q) in the observed wide sdB binaries. In the P-q plane two distinct groups emerge, with the main group (18 systems) showing a strong correlation of lower mass ratios at longer orbital periods. The second group comprises systems that are thought to be formed from higher mass progenitors. Based on theoretical models, a correlation between the initial mass ratio at the start of RLOF and core mass of the sdB progenitor is found, which defines a mass-ratio range at which RLOF is stable on the RGB.
KW  - binaries: spectroscopic
KW  - stars: evolution
KW  - stars: fundamental parameters
KW  - subdwarfs
Y1  - 2018
U6  - https://doi.org/10.1093/mnras/sty3017
SN  - 0035-8711
SN  - 1365-2966
VL  - 482
IS  - 4
SP  - 4592
EP  - 4605
PB  - Oxford Univ. Press
CY  - Oxford
ER  -