2015A&A...579A..49V


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.13CEST08:13:03

2015A&A...579A..49V - Astronomy and Astrophysics, volume 579A, 49-49 (2015/7-1)

Testing eccentricity pumping mechanisms to model eccentric long-period sdB binaries with MESA.

VOS J., OSTENSEN R.H., MARCHANT P. and VAN WINCKEL H.

Abstract (from CDS):

Hot subdwarf-B stars in long-period binaries are found to be on eccentric orbits, even though current binary-evolution theory predicts these objects to be circularised before the onset of Roche-lobe overflow (RLOF). We aim to find binary-evolution mechanisms that can explain these eccentric long-period orbits, and reproduce the currently observed period-eccentricity diagram. Three different processes are considered; tidally-enhanced wind mass-loss, phase-dependent RLOF on eccentric orbits and the interaction between a circumbinary disk and the binary. The binary module of the stellar-evolution code Modules for Experiments in Stellar Astrophysics (MESA) is extended to include the eccentricity-pumping processes. The effects of different input parameters on the final period and eccentricity of a binary-evolution model are tested with MESA. The end products of models with only tidally-enhanced wind mass-loss can indeed be eccentric, but these models need to lose too much mass, and invariably end up with a helium white dwarf that is too light to ignite helium. Within the tested parameter space, no sdBs in eccentric systems are formed. Phase-dependent RLOF can reintroduce eccentricity during RLOF, and could help to populate the short-period part of the period-eccentricity diagram. When phase-dependent RLOF is combined with eccentricity pumping via a circumbinary disk, the higher eccentricities can be reached as well. A remaining problem is that these models favour a distribution of higher eccentricities at lower periods, while the observed systems show the opposite. The models presented here are potentially capable of explaining the period-eccentricity distribution of long-period sdB binaries, but further theoretical work on the physical mechanisms is necessary.

Abstract Copyright:

Journal keyword(s): binaries: general - stars: evolution - subdwarfs - methods: numerical

CDS comments: Table 1 Bal 8280003, probably Balloon 8280003, not in SIMBAD.

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 HD 18131 Ro* 02 54 38.8239618040 -05 19 50.930526115   8.32 7.31     K0IV+DA: 57 0
2 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5669 1
3 BD+34 1543 HS* 07 10 07.7048013144 +34 24 53.813852634   10.29 10.17     sdB+F? 21 0
4 PG 1018-047 HS* 10 21 10.5823526588 -04 56 19.571214420   13.143 13.311     sdB2VIIHe0 23 0
5 PG 1104+243 HS* 11 07 26.2324426980 +24 03 11.093123426   11.49 11.39     sdOB+G2V 26 0
6 Feige 87 HS* 13 40 14.6905958545 +60 52 47.559089578   11.56 11.71     sdB+G4V 33 0
7 PG 1449+653 HS* 14 50 36.0769929096 +65 05 52.017016369   13.57 13.62 13.72   sdB+G5 23 0
8 PG 1701+359 HS* 17 03 21.4566267727 +35 48 49.249634670   13.41       sdB1VIHe0 29 0
9 BD+29 3070 HS* 17 38 21.1995850160 +29 08 47.352318979   10.55 10.45     sdOB+F/G 21 0
10 V* Z Her RS* 17 58 06.9787072966 +15 08 21.909354791   7.86 7.30     F8V 268 0
11 BD-07 5977 HS* 23 17 46.7880673139 -06 28 30.942574405   11.09 10.54     sdB 14 0

    Equat.    Gal    SGal    Ecl

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2020.07.13-08:13:03

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