Activity and Kinematics of Ultracool Dwarfs, Including an Amazing Flare Observation

By S. Schmidt, Kelle Cruz, B. Bongiorno, J. Liebert, I. Neill Reid. 2007

170 citations recorded by the source corpus.

We present the activity and kinematics of a representative volume-limited (20 pc) sample of 152 late-M and L dwarfs (M7-L8) photometrically selected from the Two Micron All Sky Survey (2MASS). Using new proper-motion measurements and spectrophotometric distance estimates, we calculate tangential velocities. The sample has a mean tangential velocity of ⟨Vtan⟩ = 31.5 km s-1, a velocity dispersion of σtan = 20.7 km s-1, and a maximum tangential velocity of Vtan = 138.8 km s-1. These kinematic results are in excellent agreement with previous studies of ultracool dwarfs in the local solar neighborhood. Hα emission, an indicator of chromospheric activity, was detected in 63 of 81 late-M dwarfs and in 16 of 69 L dwarfs examined. We find a lack of correlation between activity strength, measured by log(FHα/Fbol), and Vtan, although velocity distributions suggest that the active dwarfs in our sample are slightly younger than the inactive dwarfs. Consistent with previous studies of activity in ultracool dwarfs, we find that the fraction of Hα-emitting objects per spectral type peaks at spectral type M7 and declines through mid-L dwarfs. Activity strength is similarly correlated with spectral type for types later than M7. Eleven dwarfs out of 150 show evidence of variability, ranging from small fluctuations to large flare events. We estimate a flare cycle of ∼5% for late-M dwarfs and ∼2% for L dwarfs. Observations of strong, variable activity on the L1 dwarf 2MASS J10224821+5825453 and an amazing flare event on the M7 dwarf 2MASS J1028404-143843 are discussed.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/d643108365c5166067b26e6feba4086a311e09d9

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

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

In Education

1. A. Burgasser
2. J. D. Kirkpatrick
3. Kelle Cruz
4. Michael C. Liu
5. T. Dupuy
6. A. Reiners
7. G. Basri
8. K. Allers

In Instrumentation

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

Citations in the corpus

• CONSTRAINING THE AGE–ACTIVITY RELATION FOR COOL STARS: THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 5 LOW-MASS STAR SPECTROSCOPIC SAMPLE (2007, background): “However, the later types do not show the same decrease in activity fraction seen previously (W04; Schmidt et al. 2007).”
• 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): “In the past decade a number of groups have conducted astrometric surveys of UCDs, including subsets of low mass objects (e.g. Vrba et al. 2004, Dahn et al. 2002, Gizis et al. 2000, Tinney et al. 2003, Schmidt et al. 2007, Jameson et al. 2007, Osorio et al. 2007, and West et al. 2008, 2006).”
• THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, (2012, unknown): “…et al. (2004); (86) Reid et al. (2008b); (87) Reiners & Basri (2006); (88) Riaz et al. (2006); (89) Ruiz et al. (1991); (90) Schilbach et al. (2009); (91) Schmidt et al. (2007); (92) Schneider et al. (2002); (93) Scholz et al. (2003); (94) Scholz et al. (2004a); (95) Scholz et al. (2004b); (96)…”
• Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs (2008, background): “…emission such as Hα, providing strong evidence for magnetic reconnection events (Reid et al. 1999; Burgasser et al. 2000; Gizis et al. 2000; Rutledge et al. 2000; Liebert et al. 2003; Fuhrmeister & Schmitt 2004; Stelzer 2004; Rockenfeller et al. 2006; Stelzer et al. 2006b; Schmidt et al. 2007).”
• THE HAWAII INFRARED PARALLAX PROGRAM. II. YOUNG ULTRACOOL FIELD DWARFS (2016, background): “…et al. (2002); (72) Reid et al. (2003a); (73) Reid et al. (2008); (74) Reiners & Basri (2009); (75) Rice et al. (2010b); (76) Salim et al. (2003); (77) Schmidt et al. (2007); (78) Scholz et al. (2005); (79) Shkolnik et al. (2009); (80) Torres et al. (2003); (81) Wahhaj et al. (2011); (82)…”
• WEATHER ON OTHER WORLDS. II. SURVEY RESULTS: SPOTS ARE UBIQUITOUS ON L AND T DWARFS (2014, background): “Notably, M and early-L dwarfs are known to have elevated magnetospheric activity (Schmidt et al. 2007; Hallinan et al. 2008; Berger et al. 2010; West et al. 2011).”
• Chromospheric Activity, Rotation, and Rotational Braking in M and L Dwarfs (2008, methodology): “5 in Schmidt et al. (2007).”
• COLORS AND KINEMATICS OF L DWARFS FROM THE SLOAN DIGITAL SKY SURVEY (2010, methodology): “Previous work has found that the L dwarf population is kinematically younger than most thin disk stars but was limited either by small numbers (Zapatero Osorio et al. 2007) or by a lack of radial velocities, restricting kinematic analysis to two dimensions (Schmidt et al. 2007; Faherty et al. 2009).”
• YOUNG L DWARFS IDENTIFIED IN THE FIELD: A PRELIMINARY LOW-GRAVITY, OPTICAL SPECTRAL SEQUENCE FROM L0 TO L5 (2008, background): “While there have been several measurements of the activity fraction of L dwarfs in the field (Gizis et al. 2000; Schmidt et al. 2007), the age-activity relation for L dwarfs has not yet been studied.”
• FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, unknown): “…(114) Henry & Kirkpatrick (1990), (115) Liu et al. (2013), (116) Hawkins & Bessell (1988), (117) Looper et al. (2008b), (118) Kirkpatrick et al. (2001b), (119) Dahn et al. (2002), (120) Seifahrt et al. (2010), (121) Schmidt et al. (2007), (122) Scholz et al. (2004), (123) Chauvin et al. (2005).”
• MEETING THE COOL NEIGHBORS. X. ULTRACOOL DWARFS FROM THE 2MASS ALL-SKY DATA RELEASE (2008, background): “Schmidt et al (2007) present a thorough analysis of chromospheric activity in these low-mass dwarfs, and also discuss the proper motions and correlations between activity and kinematics.”
• BANYAN. VII. A NEW POPULATION OF YOUNG SUBSTELLAR CANDIDATE MEMBERS OF NEARBY MOVING GROUPS FROM THE BASS SURVEY (2015, background): “2MASS J03140344+1603056 was identified by Schmidt et al. (2007) as an L0 dwarf with Hα emission.”