J/ApJ/476/311 2MASS M-dwarf discoveries (Kirkpatrick+ 1997)
The coolest isolated M dwarf and other 2MASS discoveries.
Kirkpatrick J.D., Beichman C.A., Skrutskie M.F.
<Astrophys. J. 476, 311K (1997)>
=1997ApJ...476..311K 1997ApJ...476..311K (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; Stars, dwarfs ; Stars, late-type ; Photometry
Keywords: infrared: stars - stars: late-type - stars: low-mass, brown dwarfs -
surveys
Abstract:
We have obtained follow-up spectroscopy of eight late dwarf candidates
discovered in a 105deg2 area observed with the 2MASS (2 Micron
All-Sky Survey) Prototype Camera during test runs between 1992 and
1994. These objects were chosen because of their red infrared colors
(e.g., J-Ks≥1.10) and/or red OIR colors (e.g., R-Ks≥6.00). All eight
are late M dwarfs, six of which have spectral types later than van
Biesbroeck 8 (type M7 V). Despite the fact that we have only followed
up a fraction of the reddest sources discovered, the number of known M
dwarfs of type M7 and cooler has been increased by 30%. Extrapolation
of these results alone shows that over 2000 dwarfs of similar spectral
type and with Ks≤14.0 will be imaged by 2MASS over the entire sky.
One of these new discoveries is astonishingly cool and has a tentative
type of ≥M10V. This dwarf, one of the least luminous objects yet
discovered, could itself be a high-mass brown dwarf, thus providing
another empirical data point in a regime where few such objects are
now recognized. Only the substellar suspect GD 165 B and the bona fide
brown dwarf GL 229 B, both discovered as companions to known stars,
are cooler. Thus, this 2MASS discovery becomes the coolest isolated
object so far identified.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 87 8 Target list of 2MASS discoveries
table4.dat 61 8 Spectroscopic observations of 2MASS discoveries
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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- 21 A21 --- Name 2MASP name (1)
23 A1 --- l_mu Limit flag on mu
24- 28 F5.3 arcsec/yr mu ? Total Proper motion (2)
29- 30 A2 --- u_mu [: ] Uncertainty flag on mu
32- 34 I3 deg theta ? Position angle of Proper motion (2)
35- 36 A2 --- u_theta [: ] Uncertainty flag on theta
38 A1 --- l_RAPM Limit flag on RAPM
39- 43 F5.2 mag RAPM RAPM magnitude (3)
45- 49 F5.2 mag Jmag ? J magnitude
51- 54 F4.2 mag e_Jmag ? rms uncertainty on Jmag
56- 60 F5.2 mag Hmag ? H magnitude
62- 65 F4.2 mag e_Hmag ? rms uncertainty on Hmag
67- 71 F5.2 mag Ksmag Ks magnitude
73- 76 F4.2 mag e_Ksmag rms uncertainty on Ksmag
78 A1 --- l_RAPM-Ks Limit flag on RAPM-Ks
79- 82 F4.2 mag RAPM-Ks RAPM-Ks colour index
84- 87 F4.2 mag J-Ks ? J-Ks colour index
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Note (1): 2MASP Jhhmmss[.]s 1 ddmmss; Coordinate designations are in
equinox J2000.0, epoch 1993.5.
Note (2): Proper motions were determined by comparing the APM-measured position
(epoch ∼1950) to the 1993.5-epoch 2MASS position except for 2MASP
J0345432+254023, whose measurement is described in Sect. 4.1.
The values of µ and θ in all cases are referred to the
J2000.0 equinox.
Note (3): RAPM: E-plate magnitude. See Irwin et al. (1994, Spectrum 2, 14)
for more details.
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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- 21 A21 --- Name 2MASP name
23- 28 A6 --- SpType Spectral type
29 A1 --- n_SpType [b] Note on SpType (1)
31- 38 A8 "DD/MM/YY" Obs Observation date (UT)
40- 43 I4 s IntTime Integration time
45- 55 A11 --- Inst Instrument
57- 58 A2 --- l_Dist [~> ] Limit flag on Dist
59- 60 I2 pc Dist Estimated distance
61 A1 --- n_Dist [a] Not eon Dist (2)
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Note (1): b: Spectral type is tentative pending the discovery of similar
low-luminosity objects and the development of quantitative
classification criteria for objects of this late type.
Note (2): a: This distance estimate assumes that the object has an age
comparable to an average field M dwarf (∼1Gyr). If a member of
the Pleiades cluster (age∼75Myr), it will be more luminous than a
field M6.5 dwarf by ∼0.8mag at Ks and thus have a distance of
∼125pc, consistent with that of the cluster.
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Acknowledgements: From ApJ electronic version
(End) James Marcout, Patricia Bauer [CDS] 05-May-1998