J/AJ/127/2856 Brown dwarfs in the 2MASS Survey (Burgasser+, 2004)
The 2MASS wide-field T dwarf search.
III. Seven new T dwarfs and other cool dwarf discoveries.
Burgasser A.J., Mcelwain M.W., Kirkpatrick J.D., Cruz K.L., Tinney C.G.,
Reid I.N.
<Astron. J., 127, 2856-2870 (2004)>
=2004AJ....127.2856B 2004AJ....127.2856B
ADC_Keywords: Infrared sources ; Stars, dwarfs ; Photometry, infrared
Keywords: stars: fundamental parameters - stars: low-mass, brown dwarfs -
subdwarfs - techniques: spectroscopic
Abstract:
We present the discovery of seven new T dwarfs identified in the
Two Micron All Sky Survey (Cat. II/246). Low-resolution (R∼150)
0.8-2.5µm spectroscopy obtained with the Infrared Telescope
Facility (IRTF) SpeX instrument reveals the characteristic H2O and
CH4 bands in the spectra of these brown dwarfs. Comparison with
spectral standards observed with the same instrument enables us to
derive classifications of T3 to T7 for the objects in this sample.
Moderate-resolution (R∼1200) near-infrared spectroscopy for a subset
of these discoveries reveal K I line strengths consistent with
previously observed trends with spectral type. Follow-up imaging
observations provide proper-motion measurements for these sources,
ranging from less than 0.1" to 1.55"/yr. One object, 2MASS 0034+0523,
has a spectrophotometric distance placing it within 10pc of the Sun.
This source also exhibits a depressed K-band peak reminiscent of the
peculiar T dwarf 2MASS 0937+2931 and may be a metal-poor or old,
high-mass brown dwarf. We also present low-resolution SpeX data for a
set of M- and L-type dwarf, subdwarf, and giant comparison stars used
to classify 59 additional candidates identified as background stars.
These are primarily M5-M8.5 dwarfs, many exhibiting H I Paγ,
but include three candidate ultracool M subdwarfs and one possible
early-type L subdwarf.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 108 67 Log of SpeX Prism Observations: T Dwarf Candidates
table3.dat 138 33 Log of SpeX Prism Observations: Comparison Stars
refs.dat 80 23 References
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
Byte-by-byte Description of file: table2.dat table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- --- [2MASS]
7- 23 A17 --- 2MASS 2MASS name (3)
24 A1 --- m_2MASS [AB] Component
27- 31 F5.2 mag Jmag 2MASS ADR J magnitude
33- 36 F4.2 mag e_Jmag rms uncertainty on Jmag
38- 42 F5.2 mag J-H 2MASS ADR J-H colour index
44- 47 F4.2 mag e_J-H rms uncertainty on J-H
49 A1 --- l_H-Ks Limit flag on H-Ks
50- 54 F5.2 mag H-Ks 2MASS ADR H-Ks colour index
56- 59 F4.2 mag e_H-Ks ? rms uncertainty on H-Ks
61- 70 A10 "YYYY/MM/DD" Date UT observation date
72- 75 I4 s ExpTime Exposure time
77- 80 F4.2 --- AirMass Airmass
81 A1 --- --- [-]
82- 84 F3.1 --- AirMass2 ? Upper limit of airmass when interval
86- 94 A9 --- Calib Calibrator name
96-100 A5 --- SpCal MK spectral type of Calibrator
102-121 A20 --- Class Spectral Classification of star (1)
122 A1 --- n_Class [b] Note on Class for variable giants (2)
124-128 A5 --- Refs References detailed in refs.dat file
130-138 A9 --- VName Variable name (3)
--------------------------------------------------------------------------------
Note (1): Classifications are based on comparison to spectral templates
(Table 3) and for M dwarfs are accurate to within 0.5-1.0 subclasses
(see Chap. 3.1.1). Classification terms followed by a colon are more
uncertain because of poor S/N data or lack of adequate comparison stars.
Note (2):
Spectral types for variable giant stars may vary by several subclasses
over time, and given classifications may not accurately represent the
actual spectrum observed.
Note (3):
The 2MASS name has been added at CDS in the last 3 rows of table3;
the original name was shifted to the "VName" column.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Ref Reference code
4- 22 A19 --- BibCode BibCode
24- 44 A21 --- Aut Author's name
47- 76 A30 --- Com Comments
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Burgasser et al., Paper I 2003AJ....125..850B 2003AJ....125..850B
Burgasser et al., Paper II 2003AJ....126.2487B 2003AJ....126.2487B, Cat. J/AJ/126/2487
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 08-Jul-2004