J/ApJ/703/1511 Wide binaries in Taurus and Upper Sco (Kraus+, 2009)
Unusually wide binaries: are they wide or unusual?
Kraus A.L., Hillenbrand L.A.
<Astrophys. J., 703, 1511-1530 (2009)>
=2009ApJ...703.1511K 2009ApJ...703.1511K
ADC_Keywords: Stars, double and multiple ; Spectral types ; Stars, masses ;
Spectroscopy ; Proper motions
Keywords: binaries: general - binaries: visual - stars: formation -
stars: pre-main sequence - stars: statistics
Abstract:
We describe an astrometric and spectroscopic campaign to confirm
the youth and association of a complete sample of candidate wide
companions in Taurus and Upper Sco. Our survey found 15 new binary
systems (three in Taurus and 12 in Upper Sco) with separations of
3"-30" (500-5000AU) among all of the known members with masses of
2.5-0.012M☉. The total sample of 49 wide systems in these two
regions conforms to only some expectations from field multiplicity
surveys. Higher mass stars have a higher frequency of wide binary
companions, and there is a marked paucity of wide binary systems near
the substellar regime. However, the separation distribution appears to
be log-flat, rather than declining as in the field, and the mass ratio
distribution is more biased toward similar-mass companions than the
initial mass function or the field G-dwarf distribution. The maximum
separation also shows no evidence of a limit at ≲5000AU until the
abrupt cessation of any wide binary formation at system masses of
∼0.3M☉. We attribute this result to the post-natal dynamical
sculpting that occurs for most field systems; our binary systems will
escape to the field intact, but most field stars are formed in denser
clusters and undergo significant dynamical evolution. In summary, only
wide binary systems with total masses ≲0.3M☉ appear to be
"unusually wide."
Description:
We obtained intermediate-resolution optical spectra for 14 Taurus
candidates and 8 Upper Sco candidates with the Double Spectrograph on
the Hale 5m telescope at Palomar Observatory in 2006 December and 2007
May. We obtained intermediate-resolution near-infrared spectra for 11
of our Taurus candidates that were too faint and red for optical
spectroscopy. These spectra were obtained using NIRSPEC on the Keck-II
10m telescope on JD 2454398 with the NIRSPEC-7 (K) filter. We obtained
high-precision astrometric measurements for a subset of our candidate
companion sample in the course of several adaptive optics observing
runs at the Keck-II 10m telescope and the Palomar Hale 200 inch
telescope; for faint targets, images were obtained using the K' filter
at Keck or the Ks filter at Palomar, for brighter targets, we used the
Brγ filter.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 82 50 Candidate wide companions in Taurus and Upper Sco
table3.dat 110 33 Previously confirmed field stars
table6.dat 123 204 Astrometric data
table7.dat 57 30 Companion kinematics
table8.dat 68 50 Status determinations
table9.dat 99 48 Binary properties
refs.dat 78 48 References
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See also:
J/A+A/527/A24 : Spectra of low-mass stars in Upper Sco (Lodieu+, 2011)
J/PASJ/60/209 : Faint companions around YSOs in TMC (Itoh+, 2008)
J/ApJ/662/413 : 2MASS survey of wide multiplicity in 3 associations (Kraus+,
2007)
J/AJ/131/3016 : Low-mass objects in Upper Scorpius (Slesnick+, 2006)
J/ApJ/645/676 : Spatial distribution of brown dwarfs in Taurus (Luhman+, 2006)
J/AJ/129/2294 : Radial velocities of T Tauri stars (Massarotti+, 2005)
J/AJ/124/404 : Upper Scorpius OB association Lithium survey. II. (Preibisch,
2002)
J/AJ/120/479 : Low-mass stars in the Upper Sco association (Ardila+, 2000)
J/A+A/356/541 : T Tauri stars in the Sco-Cen OB association (Koehler+, 2000)
J/A+A/325/647 : High-resolution spectra south of Taurus (Neuhaeuser+ 1997)
J/ApJS/101/117 : UBVRIJHKLMNQ photometry in Taurus-Auriga (Kenyon+ 1995)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Cloud Cloud name ("Taurus" or "Upper Sco")
11- 32 A22 --- Name Known member name (G1)
34- 51 A18 --- Comp Candidate companion name (G1)
53- 57 F5.2 arcsec Sep Separation between the two objects
59- 63 F5.1 deg PA Position angle
65- 69 F5.2 mag DelK Observed flux ratio ΔK
71- 79 A9 --- SpType Known MK spectral type (G2)
81- 82 I2 --- Ref Reference (see refs.dat file)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Cloud Cloud name ("Taurus" or "Upper Sco")
11- 31 A21 --- Name Primary name
33- 53 A21 --- Comp Secondary name
55- 60 F6.3 arcsec Sep Separation between the two objects
62- 66 F5.1 deg PA Position angle
68- 72 F5.2 mag DelK Observed flux ratio ΔK
74- 85 A12 --- SpT1 Primary MK spectral type (G2)
87- 95 A9 --- SpT2 Secondary MK spectral type (G2)
97-110 A14 --- Ref Reference(s)
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- DType Data type (New or Archival)
10- 31 A22 --- Name Known member identification
33- 50 A18 --- Comp Candidate companion identification
52- 56 I5 d Epoch Epoch of observation; JD-2400000
58- 62 I5 mas Sep Separation
64- 66 I3 mas e_Sep Uncertainty in Sep
68- 73 F6.2 deg PA Position angle
75- 78 F4.2 deg e_PA Uncertainty in PA
80-123 A44 --- Source Source
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 22 A22 --- Name Known member name
24- 41 A18 --- Comp Candidate companion name
43- 47 F5.1 mas/yr mua Relative proper motion in RA (1)
49- 53 F5.1 mas/yr mud Relative proper motion in DE (1)
55- 57 F3.1 mas/yr e_mu 1σ error on relative proper motion (1)
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Note (1): As we discuss in Section 4.3, many of the proper motions that
rely on high-precision astrometry could be more uncertain due to
uncorrected systematic effects (such as detector distortion) and
astrophysical jitter (such as from unresolved high-order multiplicity).
A factor of ∼2 increase in the proper motion uncertainty would bring
our uncertainties in line with the observed scatter.
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Set ΔK <3 or >3
4- 25 A22 --- Name Known member name
27- 44 A18 --- Comp Candidate companion name
46- 47 A2 --- Sp [YN? ] Membership spectroscopic determination
49- 50 A2 --- As [YN? ] Membership astrometric determination
52 A1 --- F [YN] Membership final determination
54 A1 --- l_SpT [~< ] Limit flag on SpT
55- 61 A7 --- SpT MK spectral type
63- 68 F6.1 0.1nm W(Ha) ? Hα equivalent width
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Set Known or New
7- 27 A21 --- Name Primary name
28 A1 --- f_Name [b] Secondary more massive (1)
30- 50 A21 --- Comp Secondary name
52- 55 F4.2 Msun M1a Primary mass of component 1 (2)
57- 61 F5.3 Msun M1b ? Primary mass of component 2 (2)
62 A1 --- f_M1b [w] Sources without spectral types (3)
64- 67 F4.2 Msun M1c ? Primary mass of component 3 (2)
68 A1 --- f_M1c [w] Sources without spectral types (3)
70- 73 F4.2 Msun M1d ? Primary mass of component 4 (2)
74 A1 --- f_M1d [w] Sources without spectral types (3)
76- 80 F5.3 Msun M2a Secondary mass of component 1 (2)
81 A1 --- f_M2a [w] Sources without spectral types (3)
83- 87 F5.3 Msun M2b ? Secondary mass of component 2 (2)
88 A1 --- f_M2b [w] Sources without spectral types (3)
90- 94 F5.3 --- q Ms/Mp mass ratio (4)
96- 99 I4 AU r Separation in AU
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Note (1): b = Several newly identified companions appear to be more massive
than the known member, suggesting that the known member is the binary
secondary. In cases where the known member had a generic name (i.e.,
USco80), we have appropriated that name for the new member to avoid
name proliferation in the literature. For systems with
coordinate-based names, we have used the 2MASS name of the new member
to avoid confusion over coordinates.
Note (2): Masses for all members with known spectral types were estimated
using the mass-SpT relations described in Section 3.5.
Note (3): Masses were estimated using the estimated mass of the system
primary and the measured flux ratio. The references for these flux
ratios are listed in Tables 1 and 3.
Note (4): For hierarchical multiple systems, we computed the mass ratio by
summing the individual stellar masses in all subcomponents of the wide
"primary" and "secondary." Our model-dependent masses are uncertain to
∼20%, and the mass ratios and projected separations have typical
uncertainties of ∼10%. Finally, some hierarchical multiple systems
have mass ratios q>1, where the combined mass for all components of B
is higher than that of A. We preserve the existing naming scheme for
continuity, but will invert this mass ratio during our analysis
(Section 5) to reflect that B is the most massive component.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference number
4- 22 A19 --- BibCode Bibcode
24- 42 A19 --- Aut Author's name(s)
44- 78 A35 --- Comm Comment
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Global notes:
Note (G1): The astrometry and photometry for each candidate system have
been adopted from our re-reduction of the 2MASS atlas images (Kraus &
Hillenbrand, 2007, Cat. J/ApJ/662/413).
Note (G2): Entries with multiple spectral types denote components which are
themselves known to be multiple; if the spectral type for a component
has not been measured, it is listed as "?". Sources labeled "cont"
only exhibit continuum emission from accretion and disk emission, with
no recognizable spectral features.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 26-Oct-2011