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 (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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 87 8 Target list of 2MASS discoveries table4.dat 61 8 Spectroscopic observations of 2MASS discoveries
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
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 R_APM_ 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
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.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
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)
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.
Acknowledgements: From ApJ electronic version
(End) James Marcout, Patricia Bauer [CDS] 05-May-1998
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