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  - 
TY  - JOUR
A1  - Vos, Joris
A1  - Vuckovic, Maja
A1  - Chen, X.
A1  - Han, Zh
A1  - Boudreaux, Thomas
A1  - Barlow, Brad N.
A1  - Ostensen, R.
A1  - Nemeth, Péter
T1  - Using wide hot subdwarf binaries to constrain Roche-lobe overflow models
JF  - Contributions of the Astronomical Observatory Skalnaté Pleso
N2  - Hot subdwarf B (sdB) stars are evolved core helium burning stars that have lost most of their hydrogen envelope due to binary interaction on the red giant branch. As sdB stars in wide binary systems can only be created by stable Roche lobe overflow, they are a great test sample to constrain the theoretical models for stable mass loss on the red giant branch. We present here the findings of a long term monitoring program of wide sdB+MS binaries. We found two main features in the orbital parameters. The majority of the systems have eccentric orbits with systems on longer orbital period having a higher eccentricity. As these systems have undergone mass loss near the tip of the RGB, tidal circularisation theory predicts them to be circularized. Our observations suggest that efficient eccentricity pumping mechanisms are active during the mass loss phase. Secondly we find a strong correlation between the mass ratio and the orbital period. Using binary evolution models, this relation is used to derive both an upper and lower limit on the initial mass ratio at which RLOF will be stable. These limits depend on the core mass of the sdB progenitor.
KW  - stars: subdwarfs
KW  - stars: binaries: spectroscopic
KW  - stars: fundamental parameters
KW  - stars: evolution
Y1  - 2019
SN  - 1335-1842
SN  - 1336-0337
VL  - 49
IS  - 2
SP  - 264
EP  - 270
PB  - Astronomický Ústav SAV
CY  - Tatranská Lomnica
ER  -