A stellar census in globular clusters with MUSE: Binaries in NGC 3201. (arXiv:1909.04050v1 [astro-ph.SR])

A stellar census in globular clusters with MUSE: Binaries in NGC 3201. (arXiv:1909.04050v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Giesers_B/0/1/0/all/0/1">Benjamin Giesers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kamann_S/0/1/0/all/0/1">Sebastian Kamann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dreizler_S/0/1/0/all/0/1">Stefan Dreizler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Husser_T/0/1/0/all/0/1">Tim-Oliver Husser</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Askar_A/0/1/0/all/0/1">Abbas Askar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gottgens_F/0/1/0/all/0/1">Fabian G&#xf6;ttgens</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brinchmann_J/0/1/0/all/0/1">Jarle Brinchmann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Latour_M/0/1/0/all/0/1">Marilyn Latour</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weilbacher_P/0/1/0/all/0/1">Peter M. Weilbacher</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wendt_M/0/1/0/all/0/1">Martin Wendt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Roth_M/0/1/0/all/0/1">Martin M. Roth</a>

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_sun, (4.4+-2.8) M_sun, and refine the
minimum mass estimate on the already published BH to (4.53+-0.21) M_sun. These
BHs are consistent with an extensive BH subsystem hosted by NGC 3201.

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_sun, (4.4+-2.8) M_sun, and refine the
minimum mass estimate on the already published BH to (4.53+-0.21) M_sun. These
BHs are consistent with an extensive BH subsystem hosted by NGC 3201.

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