J/ApJ/731/8 Multiple star formation in Taurus-Auriga (Kraus+, 2011)
Mapping the shores of the brown dwarf desert.
II. Multiple star formation in Taurus-Auriga.
Kraus A.L., Ireland M.J., Martinache F., Hillenbrand L.A.
<Astrophys. J., 731, 8 (2011)>
=2011ApJ...731....8K 2011ApJ...731....8K
ADC_Keywords: Stars, late-type ; Stars, double and multiple ; Stars, masses ;
Spectral types ; Photometry
Keywords: binaries: general - brown dwarfs - stars: low-mass -
stars: pre-main sequence
Abstract:
We have conducted a high-resolution imaging study of the Taurus-Auriga
star-forming region in order to characterize the primordial outcome of
multiple star formation and the extent of the brown dwarf desert. Our
survey identified 16 new binary companions to primary stars with
masses of 0.25-2.5M☉, raising the total number of binary pairs
(including components of high-order multiples) with separations of
3-5000AU to 90. We find that ∼2/3-3/4 of all Taurus members are
multiple systems of two or more stars, while the other ∼1/4-1/3 appear
to have formed as single stars; the distribution of high-order
multiplicity suggests that fragmentation into a wide binary has no
impact on the subsequent probability that either component will
fragment again. The separation distribution for solar-type stars
(0.7-2.5M☉) is nearly log-flat over separations of 3-5000AU, but
lower-mass stars (0.25-0.7M☉) show a paucity of binary
companions with separations of ≳200AU. Across this full mass range,
companion masses are well described with a linear-flat function; all
system mass ratios (q=MB/MA) are equally probable, apparently
including substellar companions. Our results are broadly consistent
with the two expected modes of binary formation (free-fall
fragmentation on large scales and disk fragmentation on small scales),
but the distributions provide some clues as to the epochs at which the
companions are likely to form.
Description:
We compiled a then-current (though still incomplete) stellar census in
two previous works (Kraus & Hillenbrand 2007, Cat. J/ApJ/662/413 and
2008ApJ...686L.111K 2008ApJ...686L.111K), and have used that census as the basis for our
aperture-masking sample.
We observed our survey targets over the course of two observing runs
at Keck (in 2007 November and 2008 December) and one observing run at
Palomar (in 2007 November). All of our targets were observed with the
facility AO imagers, Keck/NIRC2 and Palomar/PHARO, which have aperture
masks installed in cold filter wheels at or near the pupil stop. Most
observations were conducted using the K' or Ks filters, but we
observed the brightest targets in both H and L'.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 116 152 Stars in Taurus-Auriga with SpType ≤M4
table2.dat 122 26 Observed groups
table4.dat 64 123 Companion detection limits
table5.dat 77 89 Derived properties for class II/III binaries in
Taurus
table6.dat 140 211 Compiled detection limits for companions
refs.dat 70 54 References
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See also:
I/297 : NOMAD Catalog (Zacharias+ 2005)
J/ApJ/703/1511 : Wide binaries in Taurus and Upper Sco (Kraus+, 2009)
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/132/2665 : QUEST2 BRI photometry of Taurus-Auriga PMS (Slesnick+, 2006)
J/ApJ/645/676 : Spatial distribution of BDs in Taurus (Luhman+, 2006)
J/A+A/446/485 : New very low-mass members in Taurus (Guieu+, 2006)
J/AJ/129/2294 : RVs of weak-lines T Tauri stars (Massarotti+, 2005)
J/ApJ/593/1093 : IC 348 membership (Luhman+, 2003)
J/A+A/369/249 : T Tauri binary systems orbital motion (Woitas+, 2001)
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- 47 A47 --- Class Classification (Observed Members, Other Stars
Observed, or Not Reobserved)
49- 63 A15 --- Name Object name
64 A1 --- f_Name [b] spectroscopic binary (1)
67 I1 h RAh [3/5] 2MASS Hour of Right Ascension (J2000)
69- 70 I2 min RAm [3/56] 2MASS Minute of Right Ascension (J2000)
72- 76 F5.2 s RAs 2MASS Second of Right Ascension (J2000)
78 A1 --- DE- [+] 2MASS Sign of Declination (J2000)
79- 80 I2 deg DEd [16/32] 2MASS Degree of Declination (J2000)
82- 83 I2 arcmin DEm [0/59] 2MASS Arcminute of Declination (J2000)
85- 88 F4.1 arcsec DEs 2MASS Arcsecond of Declination (J2000)
90- 94 A5 --- SpT MK spectral type
96- 99 F4.1 mag Rmag [7/19.3]? NOMAD R band magnitude; Zacharias+
2004, Cat. I/297 (2)
101-105 F5.2 mag Ksmag [4.23/12.5] 2MASS Ks band magnitude (2)
107-113 A7 --- Group Group (3)
115-116 I2 --- Ref ? Reference (see refs.dat file)
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Note (1):
b = Short-period spectroscopic binary, as characterized by
Mathieu et al. (1997AJ....113.1841M 1997AJ....113.1841M) for DQ Tau AB, Prato et al.
(2002ApJ...579L..99P 2002ApJ...579L..99P) for UZ Tau Aab, White & Hillenbrand
(2005ApJ...621L..65W 2005ApJ...621L..65W) for StHa 34 Aab, and Massarotti et al.
(2005, Cat. J/AJ/129/2294) for V826 Tau AB. For our analysis, the
component masses of spectroscopic binaries will be combined and
treated as a single higher mass.
Note (2): Magnitudes are uncertain by ∼0.25mag and ∼0.03mag for R and K,
respectively.
Note (3): Our survey targets were observed in groups, such that single targets
could be used as calibrators for newly-discovered binaries. We also
list the composition of these groups in Table 2.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Date Observation season (Fall 2007 or Fall 2008)
11- 12 A2 --- Group Group identifier
14- 17 A4 --- Tel Telescope (Keck or Palomar (Pal))
19- 20 A2 --- Filt Filter (Lp, Kp, Ks or Hc)
22- 28 F7.1 d MJD [54427.3/54823.5] MJD epoch of the observation
30-122 A93 --- Stars Target star identifiers
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Primary name
17- 23 A7 --- Tel Telescope used (Keck or Palomar)
25- 26 A2 --- Filt Filter used (Lp, Kp, Ks or Hc)
28- 34 F7.1 d Epoch [54427.3/54823.5] MJD epoch of the observation
36- 39 F4.2 mag d10-20 Differential magnitude at ρ=10-20mas (1)
41- 44 F4.2 mag d20-40 Differential magnitude at ρ=20-40mas (1)
46- 49 F4.2 mag d40-80 Differential magnitude at ρ=40-80mas (1)
51- 54 F4.2 mag d80-160 Differential magnitude at ρ=80-160mas (1)
56- 59 F4.2 mag d160-240 Differential magnitude at ρ=160-240mas (1)
61- 64 F4.2 mag d240-320 Differential magnitude at ρ=240-320mas (1)
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Note (1): Each column reports the detection limit (in terms of flux ratio
Δm) for a bin with the given range of projected separations.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Name1 Primary name
19- 35 A17 --- Name2 Secondary name
37- 40 F4.2 Msun M1 Primary mass (1)
42 A1 --- f_M2 [r] r : SMass calculated from PMass and q (1)
43- 46 F4.2 Msun M2 Secondary mass (1)
48- 51 F4.2 --- q Mass ratio M2/M1 (2)
53- 58 F6.1 AU Sep Projected physical separation (3)
60- 74 A15 --- Type q type (2)
76- 77 I2 --- Ref Reference (see refs.dat file)
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Note (1): The primary mass was determined from its corresponding spectral type,
as described in Section 3.3. A majority of the secondary masses were
determined from the primary mass and the calculated mass ratio
(r flag), but many were directly calculated from measured spectral
type of the secondary component. The uncertainties are likely to be
∼20% and are set by systematic uncertainties from the models and the
highly uncertain ages of Taurus members.
Note (2): As we describe in Section 3.3, the mass ratio of each system was
estimated from the mass-spectral-type relation described in the text
(SpT-M), a dynamical mass measurement (DynM), or from the flux ratio
(ΔI, ΔH, or ΔK). For some hierarchical multiple
systems, several techniques were required to estimate all component
masses. The uncertainties are likely to be σq∼0.1, but could
be much larger if there are edge-on disks or unresolved components
that have not been identified.
Note (3): As we discuss in Section 3.3, projected physical separations are
determined from the projected angular separations and the mean
distance to Taurus. Projected physical separations are uncertain by
∼15% due to the finite spread of distances to Taurus members (∼20pc).
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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- 18 A18 --- Name Primary name
20- 23 F4.2 Msun Mass Mass
25- 29 F5.3 --- d13.8 Detection limit, ms/mp, for ρ=13.8mas
31- 35 F5.3 --- d17.3 Detection limit, ms/mp, for ρ=17.3mas
37- 41 F5.3 --- d21.8 Detection limit, ms/mp, for ρ=21.8mas
43- 47 F5.3 --- d27.5 Detection limit, ms/mp, for ρ=27.5mas
49- 53 F5.3 --- d34.6 Detection limit, ms/mp, for ρ=34.6mas
55- 59 F5.3 --- d43.5 Detection limit, ms/mp, for ρ=43.5mas
61- 65 F5.3 --- d54.8 Detection limit, ms/mp, for ρ=54.8mas
67- 71 F5.3 --- d69.0 Detection limit, ms/mp, for ρ=69.0mas
73- 77 F5.3 --- d86.8 Detection limit, ms/mp, for ρ=86.8mas
79- 83 F5.3 --- d138 Detection limit, ms/mp, for ρ=138mas
85- 89 F5.3 --- d218 Detection limit, ms/mp, for ρ=218mas
91- 95 F5.3 --- d346 Detection limit, ms/mp, for ρ=346mas
97-101 F5.3 --- d690 Detection limit, ms/mp, for ρ=690mas
103-107 F5.3 --- d1376 Detection limit, ms/mp, for ρ=1376mas
109-113 F5.3 --- d2746 Detection limit, ms/mp, for ρ=2746mas
115-119 F5.3 --- d5478 Detection limit, ms/mp, for ρ=5478mas
121-125 F5.3 --- d10930 Detection limit, ms/mp, for ρ=10930mas
127-131 F5.3 --- d27455 Detection limit, ms/mp, for ρ=27455mas
133-140 A8 --- Ref Reference(s) (see refs.dat file) (1)
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Note (1): All observation limits include our wide binary results from
Kraus & Hillenbrand (2007, Cat. J/ApJ/662/413, 2009,
Cat. J/ApJ/703/1511). See other references in refs.dat file.
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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 code number
4- 22 A19 --- BibCode Bibcode
24- 42 A19 --- Aut Author's name(s)
44- 70 A27 --- Comm Comment
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History:
From electronic version of the journal
References:
Kraus et al. Paper I. 2008ApJ...679..762K 2008ApJ...679..762K
Evans et al. Paper III. 2012ApJ...744..120E 2012ApJ...744..120E
Cheetham et al. Paper IV. 2015ApJ...813...83C 2015ApJ...813...83C Cat. J/ApJ/813/83
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 12-Oct-2012