J/A+A/627/A57 ONC binary and triple stars (Jerabkova+, 2019)
When the tale comes true: multiple populations and wide binaries in the
Orion Nebula Cluster.
Jerabkova T., Beccari G., Boffin H.M.J., Petr-gotzens M.G., Manara C.F.,
Prada Moroni P.G., Tognelli E., Degl'innocenti S.
<Astron. Astrophys., 627, A57 (2019)>
=2019A&A...627A..57J 2019A&A...627A..57J (SIMBAD/NED BibCode)
ADC_Keywords: Nebulae ; Stars, double and multiple
Keywords: parallaxes -
open clusters and associations: individual: Orion Nebula Cluster -
binaries: general - stars: formation - stars: pre-main sequence -
proper motions
Abstract:
Recently published high-quality OmegaCAM photometry of the 3x3deg
around the Orion Nebula Cluster (ONC) in r, and i filters revealed
three well-separated pre-main sequences in the color-magnitude diagram
(CMD). The objects belonging to the individual sequences are
concentrated toward the center of the ONC. The authors concluded that
there are two competitive scenarios: a population of unresolved
binaries and triples with an exotic mass ratio distribution, or three
stellar populations with different ages (~=1Myr age differences).
We use Gaia DR2 in combination with the photometric OmegaCAM catalog
to test and confirm the presence of the putative three stellar
populations. We also study multiple stellar systems in the ONC for the
first time using Gaia DR2.
We selected ONC members based on parallaxes and proper motions and
take advantage from OmegaCAM photometry that performs better than Gaia
DR2 photometry in crowded regions. We identify two clearly separated
sequences with a third suggested by the data. We used Pisa stellar
isochrones to estimate ages of the stellar populations with absolute
magnitudes computed using Gaia parallaxes on a star by star basis.
(1) We confirm that the second and third sequence members are more
centrally concentrated toward the center of the ONC. In addition we
find an indication that the parallax and proper motion distributions
are different among the members of the stellar sequences. The age
difference among stellar populations is estimated to be 1-2Myr. (2) We
use Gaia proper motions and other measures to identify and remove as
many unresolved multiple system candidates as possible. Nevertheless
we are still able to recover two well-separated sequences with
evidence for the third one, supporting the existence of the three
stellar populations. (3) Due to having ONC members with negligible
fore- or background contamination we were able to identify a
substantial number of wide binary objects (separation between 1000 and
3000 au) and with relative proper motions of the binary components
consistent with zero. This challenges previously inferred values that
suggested no wide binary stars exist in the ONC. Our inferred
wide-binary fraction is ~=5%.
We confirm the three populations correspond to three separated
episodes of star formation. Based on this result, we conclude that
star formation is not happening in a single burst in this region. In
addition we identify 5% of wide-binary stars in the ONC that were
thought not to be present.
Description:
We use Gaia DR2 in combination with the photometric OmegaCAM catalog
to test and confirm the presence of the putative three stellar
populations. We also study multiple stellar systems in the ONC for the
first time using Gaia DR2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 92 5 *Identified apparent triple system candidates.
tablea1.dat 68 91 *Apparent binary stars candidates
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Note on table1.dat: The apparent triple system candidates identified based on
the projected distance.
Note on tablea1.dat: The apparent binary star objects up to 3000au separation
based on the Elbow plot, see Fig. 7. The selection was done on the projected
separation and further filtered by the requirement that both components have
an identical proper motion within the 3-σ uncertainty.
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- ID1 Gaia DR2 identification number of first star
21- 39 I19 --- ID2 Gaia DR2 identification number of second star
41- 59 I19 --- ID3 Gaia DR2 identification number of third star
61- 67 F7.5 deg a1 Semi-major axis of first star
69- 75 F7.5 deg a2 Semi-major axis of second star
77- 80 F4.1 mag Gmag1 Gaia DR2 G magnitude of first star
82- 85 F4.1 mag Gmag2 Gaia DR2 G magnitude of second star
87- 90 F4.1 mag Gmag3 Gaia DR2 G magnitude of third star
92 A1 --- Note [*] Note (1)
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Note (1): * : fulfills the additional constraint of all putative companions
having identical proper motions within 3-σ uncertainty range.
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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- 2 I2 --- Seq [1/91] Sequential number
4- 22 I19 --- ID1 Gaia DR2 identification number of first star
24- 42 I19 --- ID2 Gaia DR2 identification number of second star
44- 48 F5.3 [au] log10(a) Semi-major axis
50- 54 F5.3 arcsec Sep Separation
56- 61 F6.3 mag Gmag1 Gaia DR2 G magnitude of first star
63- 68 F6.3 mag Gmag2 Gaia DR2 G magnitude of second star
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 17-Sep-2019