J/A+A/693/A161 47 Tuc binairies MUSE properties and RVs (Muller-Horn+, 2025)
Binary properties of the globular cluster 47 Tuc (NGC 104).
A dearth of short-period binaries.
Muller-Horn J., Gottgens F., Dreizler S., Kamann S., Martens S.,
Saracino S., Ye C.S.
<Astron. Astrophys. 693, A161 (2025)>
=2025A&A...693A.161M 2025A&A...693A.161M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, double and multiple ;
Radial velocities ; Optical
Keywords: techniques: radial velocities - binaries: spectroscopic -
blue stragglers - stars: low-mass -
globular clusters: individual: 47 Tuc (NGC 104)
Abstract:
Spectroscopic observations of binary stars in globular clusters are
essential to shed light on the poorly constrained period,
eccentricity, and mass ratio distributions and to develop an
understanding of the formation of peculiar stellar objects. 47 Tuc
(NGC 104) is one of the most massive Galactic globular clusters, with
a large population of blue stragglers and with many predicted but
as-yet elusive stellar-mass black holes. This makes it an exciting
candidate for binary searches. We present a multi-epoch spectroscopic
survey of 47 Tuc with the VLT/MUSE integral field spectrograph to
determine radial velocity variations for 21699 stars. We find a total
binary fraction in the cluster of (2.4±1.0)%, consistent with
previous photometric estimates, and an increased binary fraction among
blue straggler stars, approximately three times higher than the
cluster average. We find very few binaries with periods below three
days, and none with massive dark companions. A comparison with
predictions from state-of-the-art models shows that the absence of
such short-period binaries and of binaries with massive companions is
surprising, highlighting the need to improve our understanding of
stellar and dynamical evolution in binary systems.
Description:
The observations at hand are part of a larger observational campaign
of GCs, the MUSE Galactic globular cluster survey, first presented in
Kamann et al. (2018MNRAS.473.5591K 2018MNRAS.473.5591K). The data were acquired with the
MUSE integral field spectrograph, which is mounted on the Very Large
Telescope (VLT) at the Paranal Observatory in Chile.
The observations of 47 Tuc were carried out between 2014 and 2022 and
cover the central region of the cluster to approximately the
half-light radius of 47 Tuc. They consist of 11 partially overlapping
pointings in WFM and one central NFM pointing.
The spectra extracted from all stars and epochs were fitted to derive
stellar parameters (e.g. effective temperature, surface gravity, and
metallicity) and RVs of the individual stars.
Binary properties of the systems with well-constrained orbits are
listed in tablea1.dat. RV time series data are in rvs.dat. Binary
probabilities, and stellar parameters underlying this study are in
params.dat.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 110 30 *Properties of the 30 identified binary systems
with well-constrained orbits
params.dat 86 21699 Binary probabilities, and stellar parameters
rvs.dat 71 245522 RV time series data for the 21699 sources
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Note on tablea1.dat: The Keplerian parameters were calculated using UltraNest.
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- ACS ACS identifier
9- 14 F6.4 deg RAdeg Right ascension (J2000)
16- 23 F8.4 deg DEdeg Declination (J2000)
25- 29 F5.2 mag F606W Apparent visual magnitude in the F606W filter
31- 34 F4.2 Msun Mass1 Estimated primary stellar mass
36- 39 F4.2 Msun Mass2min Estimated minimum companion stellar mass
41- 46 F6.2 d Per Period
48- 53 F6.2 d E_Per Period error (upper value)
55- 60 F6.2 d e_Per Period error (lower value)
62- 65 F4.1 km/s K RV semi-amplitude
67- 69 F3.1 km/s E_K RV semi-amplitude (upper value)
71- 73 F3.1 km/s e_K RV semi-amplitude (lower value)
75- 78 F4.2 --- e Eccentricity
80- 83 F4.2 --- E_e Eccentricity (upper value)
85- 88 F4.2 --- e_e Eccentricity (lower value)
90-110 A21 --- Notes Notes (1)
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Note (1): Stars showing an excess in Hα are marked as emission line
objects (ELO) and binaries with bimodal posterior distributions
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Byte-by-byte Description of file: params.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- MUSE MUSE identification number
9- 15 I7 --- ACS ACS identifier
17- 25 F9.7 deg RAdeg Right ascension (J2000)
27- 38 F12.8 deg DEdeg Declination (J2000)
40- 45 F6.3 mag F606W ? F606W magnitude
47- 52 F6.3 mag F814W ? F814W magnitude
54- 63 F10.8 Msun Miso ? Isochrone mass
65- 86 E22.20 --- Pbin Binary probability
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Byte-by-byte Description of file: rvs.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- MUSE MUSE identifier
9- 21 F13.8 km/s RV Radial velocity
23- 41 F19.16 km/s e_RV Radial velocity error
43- 54 F12.8 --- SNR Signal-to-noise ratio
56- 71 F16.8 d JD Observation Julian date of observation
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History:
Copied at https://zenodo.org/records/14314046
(End) Patricia Vannier [CDS] 21-May-2025