Discovery of Two Nearby Peculiar L Dwarfs from the 2MASS Proper-Motion Survey: Young or Metal-Rich?

By D. Looper, J. D. Kirkpatrick, R. Cutri, Travis S. Barman, A. Burgasser, M. Cushing, T. Roellig, M. R. McGovern, Ian S. McLean, E. Rice and 2 more. 2008

136 citations recorded by the source corpus.

We present the discovery of two nearby L dwarfs from our 2MASS proper-motion search, which uses multiepoch 2MASS observations covering ~4700 deg2 of sky. 2MASS J18212815+1414010 and 2MASS J21481628+4003593 were overlooked by earlier surveys due to their faint optical magnitudes and their proximity to the Galactic plane (10° ⩽ | b | ⩽ 15°). Assuming that both dwarfs are single, we derive spectrophotometric distances of ~10 pc, thus increasing the number of known L dwarfs within 10 pc to 10. In the near-infrared, 2MASS J21481628+4003593 shows a triangular H-band spectrum, strong CO absorption, and a markedly red J − Ks color (2.38 ± 0.06) for its L6 optical spectral type. 2MASS J18212815+1414010 also shows a triangular H-band spectrum and a slightly red J − Ks color (1.78 ± 0.05) for its L4.5 optical spectral type. Both objects show strong silicate absorption at 9-11 μm. Cumulatively, these features imply an unusually dusty photosphere for both of these objects. We examine several scenarios to explain the underlying cause for their enhanced dust content and find that a metal-rich atmosphere or a low surface gravity are consistent with these results. 2MASS J18212815+1414010 may be young (and therefore have a low surface gravity) based on its low tangential velocity of 10 km s−1. On the other hand, 2MASS J21481628+4003593 has a high tangential velocity of 62 km s−1 and is therefore likely old. Hence, high metallicity and low surface gravity may lead to similar effects.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2c5b99355d3b260ddc3511b5c0421f84534c3341

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In Astronomy and Astrophysics

1. Michael C. Liu
2. A. Burgasser
3. T. Dupuy
4. J. D. Kirkpatrick
5. K. Luhman
6. B. Bowler
7. Kelle Cruz
8. M. Marley

In Instrumentation

1. Michael C. Liu
2. A. Burgasser
3. T. Dupuy
4. J. D. Kirkpatrick
5. Kelle Cruz
6. K. Allers
7. K. Luhman
8. M. Marley

Citations in the corpus

• THE HAWAII INFRARED PARALLAX PROGRAM. II. YOUNG ULTRACOOL FIELD DWARFS (2016, background): “2MASS J21481633+4003594 (L6/L6 fld-g): Looper et al. (2008b) discovered this object, noting that its red color, peculiar near-IR spectrum, and field-gravity optical spectrum indicate an unusually dusty photosphere.”
• THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS (2012, methodology): “These objects confirm that the brightening is an intrinsic feature of brown dwarf evolution (e.g. Looper et al. 2008a; Gizis et al. 2003; Liu et al. 2006; Burgasser et al. 2006b; Burgasser 2007), however the full extent and physical explanation remain mysterious.”
• A STUDY OF THE DIVERSE T DWARF POPULATION REVEALED BY WISE (2013, background): “Many of the known red L dwarfs are early-type and have accompanying optical spectra to facilitate classification and analysis (Looper et al. 2008; Kirkpatrick et al. 2006, 2010).”
• WEATHER ON OTHER WORLDS. II. SURVEY RESULTS: SPOTS ARE UBIQUITOUS ON L AND T DWARFS (2014, background): “Looper et al. (2008b) mention unusually high atmospheric dust content as an alternate explanation for these traits, although that may also be the result from low surface gravity.”
• A NEAR-INFRARED SPECTROSCOPIC STUDY OF YOUNG FIELD ULTRACOOL DWARFS (2013, background): “5 dwarf 2M 2148+40 (Looper et al. 2008).”
• HST SPECTRAL MAPPING OF L/T TRANSITION BROWN DWARFS REVEALS CLOUD THICKNESS VARIATIONS (2013, background): “…et al. 2011; Marley et al. 2010 and progress has been made in spectroscopic modeling to separate or constrain the impact of cloud structure from other parameters (e.g. Cruz et al. 2007; Folkes et al. 2007; Looper et al. 2008; Burgasser et al. 2008; Radigan et al. 2008; Cushing et al. 2010).”
• NEAR-INFRARED SPECTROSCOPY OF THE EXTRASOLAR PLANET HR 8799 b (2010, background): “The overall best-fitting object to HR 8799 b is 2MASS J21481628+4003593, which has a J–KS color of 2.38 ± 0.06 mag and a triangular H-band shape (Looper et al. 2008; Allers et al. 2007).”
• Discovery of a warm, dusty giant planet around HIP 65426 (2017, background): “5 dwarfs 2MASS J21481628+4003593, 2MASS J035523.”
• DISCOVERIES FROM A NEAR-INFRARED PROPER MOTION SURVEY USING MULTI-EPOCH TWO MICRON ALL-SKY SURVEY DATA (2010, methodology): “Using the 2MASS J-band magnitude and the Looper et al. (2008) relation noted above, we estimate a distance of ∼35 pc.”
• COLORS AND KINEMATICS OF L DWARFS FROM THE SLOAN DIGITAL SKY SURVEY (2010, background): “Red J −KS outliers often exhibit either distinctive low gravity features, indicating that these objects are young and still collapsing (Kirkpatrick et al. 2008; Cruz et al. 2009) or evidence of dusty photospheres, which can also be attributed to young ages (Looper et al. 2008).”
• The Field Substellar Mass Function Based on the Full-sky 20 pc Census of 525 L, T, and Y Dwarfs (2020, methodology): “Looper et al. (2008a) published a list of L dwarfs believed to fall within 10 pc.”
• BANYAN. VII. A NEW POPULATION OF YOUNG SUBSTELLAR CANDIDATE MEMBERS OF NEARBY MOVING GROUPS FROM THE BASS SURVEY (2015, background): “Young Substellar Moving Group Candidate Members 25 form in the photosphere of BDs. Young BDs have a lower atmospheric pressure, which allows the formation of thick clouds higher in their atmosphere (Kirkpatrick et al. 2006; Looper et al. 2008b).”
• FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, background): “Young objects are distinguished by their very red J−KS color due to dust and clouds in or above the photosphere (Kirkpatrick et al. 2006; Looper et al. 2008b), though not all very red objects have youth indicators (Faherty et al. 2013).”
• THE BROWN DWARF KINEMATICS PROJECT I. PROPER MOTIONS AND TANGENTIAL VELOCITIES FOR A LARGE SAMPLE OF LATE-TYPE M, L, AND T DWARFS (2008, background): “…et al. 2003a, Lépine et al. 2003, Gizis & Harvin 2006, Burgasser et al. 2007b), 3) unusually blue L dwarfs (hereafter UBLs; e.g. Cruz et al. 2003, Cruz et al. 2007; Knapp et al. 2004, Chiu et al. 2006), and 4) unusually red and possibly dusty L dwarfs (e.g. Looper et al. 2008; McLean et al. 2003).”
• SpeX SPECTROSCOPY OF UNRESOLVED VERY LOW MASS BINARIES. I. IDENTIFICATION OF 17 CANDIDATE BINARIES STRADDLING THE L DWARF/T DWARF TRANSITION (2009, methodology): “In an effort to make the selection process more robust, we examined the near-infrared spectra of six resolved L/T binaries (Table 3): 2MASS J0518-2828, SDSS J0423-0414 (Burgasser et al. 2005b), SDSS J1021-0304 (Burgasser et al. 2006c), 2MASS J1404+3159 (Looper et al. 2008a), SDSS J1534+1615 (Liu et ”
• THE FIRST HUNDRED BROWN DWARFS DISCOVERED BY THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE) (2011, background): “It becomes the seventh example of this class, which now includes 2MASS J21481633+4003594 and 2MASS J18212815+1414010 from Looper et al. (2008); 2MASS J13313310+3407583, 2MASS J23174712−4838501, and 2MASS J23512200+3010540 from Kirkpatrick et al. (2010); and WISE 0206+2640 from above.”
• BANYAN. II. VERY LOW MASS AND SUBSTELLAR CANDIDATE MEMBERS TO NEARBY, YOUNG KINEMATIC GROUPS WITH PREVIOUSLY KNOWN SIGNS OF YOUTH (2013, background): “This subsample includes the 11 URLs that have been identified by Looper et al. (2008), Kirkpatrick et al. (2008), Kirkpatrick et al. (2010), Mace et al. (2013) and Thompson et al. (2013).”