J/A+A/632/A3 MUSE binaries in NGC 3201 (Giesers+, 2019)
A stellar census in globular clusters with MUSE: Binaries in NGC 3201.
Giesers B., Kamann, S., Dreizler S., Husser T.-O., Askar A., Goettgens F.,
Brinchmann J., Latour M., Weilbacher P.M., Wendt M., Roth M.M.
<Astron. Astrophys. 632, A3 (2019)>
=2019A&A...632A...3G 2019A&A...632A...3G (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, double and multiple ;
Radial velocities
Keywords: binaries: general - blue stragglers - stars: black holes -
techniques: radial velocities - techniques: imaging spectroscopy -
globular clusters: individual: NGC 3201
Abstract:
We utilize multi-epoch MUSE spectroscopy to study binaries in the core
of NGC 3201. Our sample consists of 3553 stars with 54883 spectra in
total comprising 3200 main-sequence stars up to 4 magnitudes below the
turn-off. Each star in our sample has between 3 and 63 (with a median
of 14) reliable radial velocity (RV) measurements within five years of
observations. We introduce a statistical method to determine the
probability of a star showing RV variations based on the whole
inhomogeneous RV sample. Using HST photometry and an advanced
dynamical MOCCA simulation of this specific GC we overcome
observational biases that previous spectroscopic studies had to deal
with. This allows us to infer a binary frequency in the MUSE FoV and
enables us to deduce the underlying true binary frequency of
(6.75±0.72)% in NGC 3201. The comparison of the MUSE observations
with the MOCCA simulation suggests a significant fraction of
primordial binaries. We can also confirm a radial increase of the
binary fraction towards the GC centre due to mass segregation. We
discovered that in our sample at least (57.5±7.9)% of blue straggler
stars (BSS) are in a binary system. For the first time in a study of
GCs, we were able to fit Keplerian orbits to a significant sample of
95 binaries. We present the binary system properties of eleven BSS and
show evidence that two BSS formation scenarios, the mass transfer in
binary (or triple) star systems and the coalescence due to
binary-binary interactions, are present in our data. We also describe
the binary and spectroscopic properties of four sub-subgiant (or red
straggler) stars. Furthermore, we discovered two new black hole (BH)
candidates with minimum masses (Msini) of (7.68±0.50)M☉,
(4.4±2.8)M☉, and refine the minimum mass estimate on the
already published BH to (4.53±0.21)M☉. These BHs are
consistent with an extensive BH subsystem hosted by NGC 3201.
Description:
Since 2014, 27 Galactic globular clusters were observed (PI: S.
Kamann, formerly S. Dreizler) with the integral field spectrograph
Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope
(VLT; Kamann et al. 2018MNRAS.473.5591K 2018MNRAS.473.5591K). In the wide field mode, MUSE
covers a 1'x1' field of view (FoV) with a spatial sampling of 0.2" and
a spectral sampling of 1.25Å (resolving power of 1770<R<3590) in
the wavelength range from 4750 to 9350Å. MUSE allows to extract
spectra of some thousand stars per exposure. For this paper, all
observations of NGC 3201 obtained before May 2019 were used. In
addition to the pointings listed in Kamann et al.
(2018MNRAS.473.5591K 2018MNRAS.473.5591K), a deep field was also implemented. Table 1
lists the number of visits and total integration times for the
different pointings. The data include adaptive optics (AO)
observations, the standard observing mode since the AO system was
commissioned in October 2017. The AO observations are treated in the
same way as our previous observations.The only difference is that a
wavelength window of each spectrum around the sodium lines
(5805Å-5965Å) has to be masked due to the AO laser emission. The
catalogue includes the full radial velocity sample obtained from 63
MUSE observations done for different pointings in NGC 3201 and the
orbital parameters of the 95 well constrained binaries in NGC 3201.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 34 3593 List of stars with radial velocity measurements
tablea1r.dat 69 199 Radial velocities of RR Lyr and SXP stars
(for 13 stars)
tablea1m.dat 69 54684 Radial velocities of NGC 3201 members
(for 3540 stars)
tablea1n.dat 69 444 Radial velocities of NGC 3201 nonmembers
(for 40 stars)
tablea2.dat 119 95 Orbital parameters of binaries
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See also:
J/AJ/133/1658 : ACS survey of galactic globular clusters (Sarajedini+, 2007)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Type [rmn] Type of star (1)
3- 7 I05 --- ACS The identifier in the NGC 3201 ACS catalogue
9- 19 F11.7 deg RAdeg Right ascension of star (J2000)
21- 31 F11.7 deg DEdeg Declination of star (J2000)
33- 34 I2 --- Nobs Number of observed radial velocities in
corresponding table A1
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Note (1): Type of star as follows:
r = RR Lyr and SXP stars (RV in tablea1r.dat)
m = NGC 3201 members (RV in tablea1m.dat)
n = NGC 3201 nonmembers (RV in tablea1n.dat)
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Byte-by-byte Description of file: tablea1m.dat tablea1n.dat tablea1r.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I05 --- ACS The identifier in the NGC 3201 ACS catalogue
7- 17 F11.7 deg RAdeg Right ascension of star (J2000)
19- 29 F11.7 deg DEdeg Declination of star (J2000)
31- 36 F6.3 mag F606Wmag ACS F606W magnitude of star
38- 53 F16.8 d Date Mean observation date of the combined
exposures, BJD (Barycentric Julian Date)
55- 59 F5.1 km/s BRV Barycentric corrected radial velocity of
spectrum
61- 64 F4.1 km/s e_BRV Radial velocity uncertainty
66- 69 F4.2 --- Pvar Probability that star is a binary
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I05 --- ACS The identifier in the NGC 3201 ACS catalogue
7- 17 F11.7 deg RAdeg Right ascension of star (J2000)
19- 29 F11.7 deg DEdeg Declination of star (J2000)
31- 42 F12.7 d Per Orbital period of binary system
44- 55 F12.7 d e_Per Uncertainty of period
57- 60 F4.2 --- Ecc Eccentricity of binary system
62- 65 F4.2 --- e_Ecc Uncertainty of eccentricity
67- 72 F6.2 km/s Amp Semi-amplitude of the visible component
74- 78 F5.2 km/s e_Amp Uncertainty of semi-amplitude
80- 83 F4.2 Msun Mvis Mass of visible component
85- 88 F4.2 Msun e_Mvis Uncertainty of mass of visible component
90- 93 F4.2 Msun Minvis Mass of invisible component
95- 98 F4.2 Msun e_Minvis Uncertainty of mass of invisible component
100-119 A20 --- Com Comments
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Acknowledgements:
Benjamin Giesers, giesers(at)gwdg.de
References:
Sarajedini et al., 2007AJ....133.1658S 2007AJ....133.1658S
ACS survey of galactic globular clusters, Cat. J/AJ/133/1658
(End) Patricia Vannier [CDS] 25-Sep-2019