J/A+A/703/A294 Post-RGB binaries and stable mass transfer (Moltzer+, 2025)
Understanding post-red giant branch binaries through stable mass transfer.
Moltzer C.A.S., Pols O.R., Van Winckel H., Temmink K.D., Wijdeveld M.W.
<Astron. Astrophys. 703, A294 (2025)>
=2025A&A...703A.294M 2025A&A...703A.294M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Models, evolutionary ;
Stars, standard ; Mass loss
Keywords: stars: AGB and post-AGB - binaries: close - stars: evolution -
stars: low-mass - stars: mass-loss
Abstract:
Post-red giant branch (post-RGB) and post-asymptotic giant branch
(post-AGB) binaries consist of a primary star that has recently
evolved of either the RGB or AGB after losing the majority of its
envelope and a main-sequence companion. They are distinguished by
having luminosities below and above the tip of the RGB, respectively.
These systems are characterised by the presence of a stable, dusty
circumbinary disc, identified by a near-IR excess. Observed Galactic
post-AGB and post-RGB binaries have orbital periods and eccentricities
that are at odds with binary population synthesis models. In this
work, we focus on post-RGB binaries. We investigate whether stable
mass transfer can explain the orbital periods of such binaries by
comparing stable mass transfer models with the known sample of 38
Galactic post-RGB binaries. We systematically determined the
luminosities of the Galactic post-RGB and post-AGB binary sample using
spectral energy distribution fitting. We computed evolution models for
low- and intermediate-mass binaries with RGB donors at two
metallicities using the detailed stellar evolution code, MESA. We
selected the stable mass transfer models that result in primaries with
effective temperatures within the observed range of post-RGB binaries
(4000-8500K). From our model grids, we find that low-mass post-RGB
binaries are expected to follow strict luminosity-orbital period
relations. The Galactic post-RGB binaries appear consistent with these
luminosity-orbital period relations if we assume that their orbits
remained eccentric during mass transfer and that the donor star filled
its Roche lobe at periastron. However, our models are unable to
explain the eccentricities themselves. Furthermore, the
post-mass-transfer ages of observed post-RGB binaries estimated using
our models are significantly longer than the predicted dissipation
timescales of their circumbinary discs. The stable mass transfer
formation channel appears to explain the orbital periods of Galactic
post-RGB binaries. This formation scenario could be tested more
extensively by obtaining the orbits of additional Galactic systems, as
well as those of the numerous candidates in the Magellanic Clouds,
through long-term radial velocity monitoring. Additionally, we expect
that Gaia Data Release 4 will improve the luminosities of Galactic
post-RGB binaries, which will allow for a more accurate comparison
with post-RGB luminosity-orbital period relations.
Description:
The SED fitting results, primarily the luminosity, of the Galactic
post-AGB and post-RGB binary sample, as well as of candidate samples
in the LMC and SMC, are presented. In addition, the initial parameters
of the stable mass transfer models used are given. Furthermore, for
the post-RGB binary candidates in the Magellanic Clouds, the orbital
periods estimated using the luminosity-orbital period relations, and
the post-mass-transfer ages estimated from the stable mass transfer
model grids, are presented.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec2.dat 95 85 SED fitting results of the Galactic post-AGB
and post-RGB binary sample
tablec3.dat 69 128 SED fitting results of the post-AGB and post-RGB
binary candidate samples in the LMC and SMC
tablec4.dat 24 111 Initial parameters of utilised stable mass
transfer models with Z = 0.02
tablec5.dat 24 118 Initial parameters of utilised stable mass
transfer models with Z = 0.00142
tablec7.dat 102 75 Estimated orbital periods and post-mass-transfer
ages of the post-RGB binary candidate
subsamples in the LMC and SMC
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Byte-by-byte Description of file: tablec2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- IRAS IRAS name of object
13- 32 A20 --- Name Alternative identifications of object
34- 38 I5 K Teff Effective temperature (1)
40- 44 I5 pc Dist ? Distance (2)
46- 50 I5 pc b_Dist ? 16th percentile of distance (2)
52- 56 I5 pc B_Dist ? 84th percentile of distance (2)
58- 61 F4.2 mag E(B-V) ? Reddening
63- 66 F4.2 mag b_E(B-V) ? Lower limit of reddening
68- 71 F4.2 mag B_E(B-V) ? Upper limit of reddening
73- 77 I5 Lsun Lum Luminosity (3)
79- 83 I5 Lsun b_Lum Lower limit of luminosity (3)
85- 90 I6 Lsun B_Lum Upper limit of luminosity (3)
92- 95 I4 % LIR IR-to-stellar luminosity ratio
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Note (1): These effective temperatures are taken from Kluska et al.
(2022A&A...658A..36K 2022A&A...658A..36K, Cat. J/A+A/658).
Note (2): These geometric distances are taken from Bailer-Jones et al.
(2021AJ....161..147B 2021AJ....161..147B, Cat. I/352).
Note (3): The luminosities of HD 44179 are taken from Men'shchikov et al.
(2002A&A...393..867M 2002A&A...393..867M), as no distance from Bailer-Jones et al.
(2021AJ....161..147B 2021AJ....161..147B, Cat. I/352) is available due to the lack of a Gaia
parallax measurement.
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Byte-by-byte Description of file: tablec3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Name Identification (JHHMMSS.ss+DDMMSS.s or
OGLE-LMC-T2CEP-NNN or OGLE-SMC-T2CEP-NNN)
21- 23 A3 --- Host [SMC LMC] Host Magellanic Cloud
25- 29 I5 K Teff Effective temperature
31- 34 F4.2 mag E(B-V) Reddening
36- 39 F4.2 mag b_E(B-V) Lower limit of reddening
41- 44 F4.2 mag B_E(B-V) Upper limit of reddening
46- 50 I5 Lsun Lum Luminosity
52- 56 I5 Lsun b_Lum Lower limit of luminosity
58- 62 I5 Lsun B_Lum Upper limit of luminosity
64- 67 I4 % LIR IR-to-stellar luminosity ratio
69 A1 --- Ref [a-d] Reference to the paper from which the
object was taken (1)
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Note (1): References as follows:
a = van Aarle et al. (2011A&A...530A..90V 2011A&A...530A..90V, Cat. J/A+A/530/A90)
b = Kamath et al. (2015MNRAS.454.1468K 2015MNRAS.454.1468K, Cat. J/MNRAS/454/1468)
c = Manick et al. (2018A&A...618A..21M 2018A&A...618A..21M)
d = Kamath et al. (2014MNRAS.439.2211K 2014MNRAS.439.2211K, Cat. J/MNRAS/439/2211)
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Byte-by-byte Description of file: tablec4.dat tablec5.dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 Msun Mi Initial mass
6- 11 F6.4 Msun MRLOF Mass at the onset of RLOF
13- 20 F8.4 [Rsun] logRRLOF Radius at the onset of RLOF
22- 24 F3.1 --- qmin Smallest mass ratio in the model grid for
this primary model to result in stable mass
transfer
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Byte-by-byte Description of file: tablec7.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Name Identification (JHHMMSS.ss+DDMMSS.s or
OGLE-LMC-T2CEP-NNN)
21- 23 A3 --- Host [SMC LMC] Host Magellanic Cloud
25- 28 I4 d Porbmean ? Estimated orbital period determined from
its luminosity (1)
30 I1 --- f_Porbmean [0/1] If true (1), the orbital period is a
lower limit as the luminosity of the object
is larger than the maximum luminosity of
the binary models
32- 35 I4 d Porbmin ? Estimated orbital period determined from
the lower limit of its luminosity (1)
37- 40 I4 d Porbmax ? Estimated orbital period determined from
the upper limit of its luminosity (1)
42 I1 --- f_Porbmax [0/1] If true (1), the maximum orbital
period is a lower limit as the luminosity
upper limit of the object is larger than
the maximum luminosity of the binary models
44- 50 I7 yr Agemeansol Estimated post-mass-transfer age determined
from its position in the HRD compared to
the solar model grid
52 I1 --- f_Agemeansol [0/1] If true (1), the mean
post-mass-transfer age is an upper limit,
as the luminosity of the object is larger
than the maximum luminosity of the
solar model grid
54- 60 I7 yr Ageminsol Estimated minimum post-mass-transfer age
determined from its position in the HRD
compared to the solar model grid
62 I1 --- f_Ageminsol [0/1] If true (1), the minimum
post-mass-transfer age is an upper limit,
as the luminosity lower limit of the object
is larger than the maximum luminosity of
the solar model grid
64- 70 I7 yr Agemaxsol Estimated maximum post-mass-transfer age
determined from its position in the HRD
compared to the solar model grid
72 I1 --- f_Agemaxsol [0/1] If true (1), the maximum
post-mass-transfer age is an upper limit,
as the luminosity upper limit of the object
is larger than the maximum luminosity of
the solar model grid
74- 80 I7 yr Agemeanmp Estimated post-mass-transfer age determined
from its position in the HRD compared
to the metal-poor model grid
82 I1 --- f_Agemeanmp [0/1] If true (1), the mean
post-mass-transfer age is an upper limit,
as the luminosity of the object is larger
than the maximum luminosity of the
metal-poor model grid
84- 90 I7 yr Ageminmp Estimated minimum post-mass-transfer age
determined from its position in the HRD
compared to the metal-poor model grid
92 I1 --- f_Ageminmp [0/1] If true (1), the minimum
post-mass-transfer age is an upper limit,
as the luminosity lower limit of the object
is larger than the maximum luminosity of
the metal-poor model grid
94-100 I7 yr Agemaxmp Estimated maximum post-mass-transfer age
determined from its position in the HRD
compared to the metal-poor model grid
102 I1 --- f_Agemaxmp [0/1] If true (1), the maximum
post-mass-transfer age is an upper limit,
as the luminosity upper limit of the object
is larger than the maximum luminosity of
the metal-poor model grid
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Note (1): We do not estimate the orbital periods of OGLE-LMC-T2CEP-032 and
OGLE-LMC-T2CEP-200, as these have already been photometrically determined.
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Acknowledgements:
Casper Moltzer, casper.moltzer(at)ru.nl
(End) Patricia Vannier [CDS] 10-Nov-2025