J/AJ/126/1526 IR photometry of ultracool dwarfs (Bouy+, 2003)
Multiplicity of nearby free-floating ultracool dwarfs:
a Hubble Space Telescope WFPC2 search for companions.
Bouy H., Brandner W., Martin E.L., Delfosse X., Allard F., Basri G.
<Astron. J. 126, 1526 (2003)>
=2003AJ....126.1526B 2003AJ....126.1526B
ADC_Keywords: Stars, double and multiple ; Photometry, infrared
Keywords: binaries: general - stars: low-mass, brown dwarfs
Abstract:
We present Hubble Space Telescope (HST) Wide Field Planetary Camera 2
(WFPC2) observations of a sample of 134 ultracool objects (spectral
types later than M7) coming from the Deep Near Infrared Survey
(DENIS), Two Micron All Sky Survey (2MASS), and Sloan Digital Sky
Survey (SDSS), with distances estimated to range from 7 to 105pc.
Fifteen new ultracool binary candidates are reported here. Eleven
known binaries are confirmed, and orbital motion is detected in some
of them. We estimate that the closest binary systems in this sample
have periods between 5 and 20yr, and thus dynamical masses will be
derived in the near future. For the calculation of binary frequency,
we restrict ourselves to systems with distances less than 20pc. After
correction of the binaries bias, we find a ratio of visual binaries
(at the HST limit of detection) of around 10%, and that 15% of the 26
objects within 20pc are binary systems with separations between 1 and
8AU. The observed frequency of ultracool binaries is similar to that
of binaries with G-type primaries in the separation range from 2.1 to
140AU. There is also a clear deficit of ultracool binaries with
separations greater than 15AU, and a possible tendency for the
binaries to have mass ratios near unity. Most systems have indeed
visual and near-infrared brightness ratios between 1 and 0.3. We
discuss our results in the framework of current scenarios for the
formation and evolution of free-floating brown dwarfs.
Description:
The observations occurred between 2000 February and 2001 August during
HST cycles 8 and 9. They have been carried out in snapshot mode. Each
object was observed with the Planetary Camera of HST/WFPC2 in the
F675W (600s) and F814W (300s) for our own program, in the F606W (100s)
and F814W (300s+350s) filters for program GO 8146 and in the F814W
(100s, 200s, or 400s) and F1042M (500s) filters for program GO 8581.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 113 133 List of Targets
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See also:
B/denis : The DENIS database (DENIS Consortium, 2003)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/AJ/123/3409 : SDSS M, L, and T dwarfs (Hawley+, 2002)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- PID Program identification
8- 30 A23 --- Name Object name
32- 33 A2 --- f_Name Binarity (1)
35- 36 I2 h RAh Hour of Right Ascension (J2000)
38- 39 I2 min RAm Minute of Right Ascension (J2000)
41- 44 F4.1 s RAs Second of Right Ascension (J2000)
46 A1 --- DE- Sign of the Declination (J2000)
47- 48 I2 deg DEd Degree of Declination (J2000)
50- 51 I2 arcmin DEm Arcminute of Declination (J2000)
53- 56 F4.1 arcsec DEs Arcsecond of Declination (J2000)
60 A1 --- l_SpType [~<] Limit or approximate flag on SpType
61- 64 A4 --- SpType Spectral type
66 A1 --- n_SpType [b] Note on SpType (2)
68- 72 F5.2 mag Imag ? The I band magnitude
74- 78 F5.2 mag Jmag ? The J band magnitude
80- 84 F5.2 mag Hmag ? The H band magnitude
86- 90 F5.2 mag Kmag ? The Ks band magnitude
92-101 A10 "YYYY/MM/DD" ObsDate Date of the observation
103-107 F5.1 pc Dist ? Estimated distance as explained in
the text
109 A1 --- n_Dist [o] trigonometric parallax (3)
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Note (1): Note on Name as follows:
* = previously known binaries
** = new multiple system candidate presented in this paper
Note (2): b = Spectral Types estimated using the SpT vs. (I-J) relation
given in Dahn et al. (2002AJ....124.1170D 2002AJ....124.1170D).
Note (3): o = trigonometric parallax (Dahn et al., 2002AJ....124.1170D 2002AJ....124.1170D;
Perryman et al., Hipparcos catalog I/239, 1997A&A...323L..49P 1997A&A...323L..49P).
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History:
* 16-Oct-2003: From electronic version of the journal
* 31-Jan-2006: SDSS154831.7+0029415 corrected into
SDSS154831.7-0029415
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 16-Oct-2003