J/A+A/690/A178 Binary fraction of M17 (Ramirez-Tannus+, 2024)
The spectroscopic binary fraction of the young stellar cluster M17.
Ramirez-Tannus M.C., Derkink A.R., Backs F., de Koter A., Sana H.,
Poorta J., Kaper L., Stoop M.
<Astron. Astrophys. 690, A178 (2024)>
=2024A&A...690A.178R 2024A&A...690A.178R (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; H II regions ; Radial velocities ; Optical
Keywords: binaries: close - binaries: spectroscopic - stars: early-type -
stars: formation - stars: pre-main sequence -
open clusters and associations: general
Abstract:
Significant progress has been made toward understanding the formation
of massive (M>8M☉) binaries in close orbits (with periods of
less than a month). Some of the observational studies leading to this
progress are the detection of a very low velocity dispersion among the
massive stars in the young region M17 and the measurement of a
positive trend of velocity dispersion with age in Galactic clusters.
The velocity dispersion observed in M17 could be explained either by
the lack of binaries among the stars in this region, which implies the
highly unlikely scenario of a different formation mechanism for M17
than for other Galactic regions, or by larger binary separations than
typically observed, but with a binary fraction similar to other young
Galactic clusters.
The latter implies that over time, the binary components migrate
toward each other. This is in agreement with the finding that the
radial velocity dispersion of young Galactic clusters correlates
positively with their age. We aim to determine the origin of the
strikingly low velocity dispersion by determining the observed and
intrinsic binary fraction of massive stars in M17 through multi-epoch
spectroscopy.
We performed a multi-epoch spectroscopic survey consisting of three
epochs separated by days and months, respectively. We complement this
survey with existing data covering timescales of years. We determine
the radial velocity of each star at each epoch by fitting the stellar
absorption profiles. The velocity shifts between epochs are used to
determine whether a close companion is present.
We determine an observed binary fraction of 27% and an intrinsic
binary fraction of 87%, consistent with that of other Galactic
clusters. We conclude that the low velocity dispersion is due to a
large separation among the young massive binaries in M17. Our result
is in agreement with a migration scenario in which massive stars are
born in binaries or higher order systems at large separation and
harden within the first million years of evolution. Such an inward
migration may either be driven by interaction with a remnant accretion
disk, with other young stellar objects present in the system or by
dynamical interactions within the cluster.
Our results imply that possibly both dynamical interactions and binary
evolution are key processes in the formation of gravitational wave
sources.
Description:
Log of the observations used in this paper. The first column lists the
name of the object, the second and third list the right ascension and
declination (J2000), the fourth and fifth list the date of observation
and it's corresponding Julian date and the sixth column lists the
barycentric radial velocity for each observation.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
obslog.dat 56 74 Log of observations
rv.dat 45 74 Radial velocity measurements
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See also:
II/320 : Variable stars in the M16-M17 field (Maffei+ 1999)
J/ApJS/169/353 : Chandra sources in M17 (Broos+, 2007)
J/ApJ/696/1278 : The extended star-forming environment of M17 (Povich+, 2009)
J/ApJ/714/L285 : YSO candidates in M17 SWex (Povich+, 2010)
J/A+A/604/A78 : M17 massive pms stars X-shooter spectra (Ramirez-Tannus+ 2017)
J/AJ/163/276 : Compact radio sources in M17 X-band observations (Yanza+ 2022)
Byte-by-byte Description of file: obslog.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Source Source name
7- 13 F7.3 deg RAdeg Right ascension (J2000.0)
15- 21 F7.3 deg DEdeg Declination (J2000.0)
23- 32 A10 "date" Date Observation date
34- 48 F15.9 d MJD Modified Julian Date
50- 56 F7.3 km/s BRV Barycentric radial velocity
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Byte-by-byte Description of file: rv.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Source Source name
7- 21 F15.9 d MJD Modified Julian Date
23- 27 F5.1 km/s RVISM Radial velocity of interstellar lines
29- 31 F3.1 km/s e_RVISM RV of interstellar lines uncertainty
33- 38 F6.1 km/s RV ?=-999 Radial velocity
40- 45 F6.1 km/s e_RV ?=-999 Radial velocity uncertainty
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Acknowledgements:
Maria Claudia Ramirez-Tannus, ramirez(at)mpia.de
(End) M.C. Ramirez-Tannus [MPIA, Heidelberg], P. Vannier [CDS] 17-Aug-2024