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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
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 138 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 Burgasser et al., Paper II 2003AJ....126.2487B, Cat. J/AJ/126/2487
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 08-Jul-2004
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