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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
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: 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:
FileName Lrecl Records Explanations
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
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
Bytes Format Units Label Explanations
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)
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
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)
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
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)
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.
Byte-by-byte Description of file: table8.dat
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table9.dat
Bytes Format Units Label Explanations
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
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.
Byte-by-byte Description of file: refs.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Ref Reference number 4- 22 A19 --- BibCode Bibcode 24- 42 A19 --- Aut Author's name(s) 44- 78 A35 --- Comm Comment
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.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 26-Oct-2011
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