2MASS J12195156+3128497

2MASS J12195156+3128497 (abbreviated to 2MASS J1219+3128) is a rapidly-rotating brown dwarf of spectral class L8, located in the constellation Coma Berenices about 66 light-years from Earth. With a photometrically measured rotation period of 1.14 hours, it is one of the fastest-rotating known brown dwarfs announced by a team of astronomers led by Megan E. Tannock in March 2021. With a rotational velocity of about 80 km/s (50 mi/s), it is approaching the predicted rotational speed limit beyond which it would break apart due to centripetal forces. As a consequence of its rapid rotation, the brown dwarf is slightly flattened at its poles to a similar degree as Saturn, the most oblate planet in the Solar System.[5] Its rapid rotation may enable strong auroral radio emissions via particle interactions in its magnetic field, as observed in other known rapidly-rotating brown dwarfs.[2]

2MASS J12195156+3128497
Observation data
Epoch J2000      Equinox J2000
Constellation Coma Berenices
Right ascension 12h 19m 51.561s[1]
Declination +31° 28′ 49.714″[1]
Characteristics
Spectral type L8[2]
Apparent magnitude (J) 15.913 ± 0.082[1]
Apparent magnitude (H) 14.907 ± 0.074[1]
Apparent magnitude (K) 14.305 ± 0.072[1]
Astrometry
Radial velocity (Rv)−19.0 ± 4.2[2] km/s
Proper motion (μ) RA: –233.0 ± 23.7[3] mas/yr
Dec.: –49.6 ± 14.7[3] mas/yr
Distance66.2 ± 9.8 ly
(20.3 ± 3.0[4] pc)
Details[2]
Mass0.047+0.022
−0.025 M☉
Radius0.100+0.027
−0.013 R☉
Surface gravity (log g)5.1 ± 0.5 cgs
Temperature1330 ± 140 K
Rotation1.14+0.03
−0.01 h
Rotational velocity (v sin i)79.0 ± 3.4 km/s
Age0.9+12.8
−0.8 Gyr
Other designations
WISE J121951.32+312849.5, UGCS J121951.36+312849.4, SDSS J121951.45+312849.4, TIC 139087399[1]
Database references
SIMBADdata

Discovery

2MASS J1219+3128 was first catalogued as a point source in June 2003 by the Two Micron All-Sky Survey (2MASS) organized by the University of Massachusetts Amherst and the Infrared Processing and Analysis Center under the California Institute of Technology.[6] It was discovered to be a brown dwarf of the spectral class L8 by K. Chiu and collaborators, based on near-infrared observations obtained from the Sloan Digital Sky Survey (SDSS) at Apache Point Observatory in New Mexico, United States. Their discovery and classification of 71 L and T dwarfs including 2MASS J1219+3128 (designated alternatively as SDSS J121951.45+312849.4) was published in The Astronomical Journal in June 2006.[7]

Distance

The distance of 2MASS J1219+3128 from Earth has not yet been measured with trigonometric parallax, so instead it is calculated from the spectrophotometric relation of spectral type and near-infrared absolute magnitude.[4] Schmidt et al. (2010) estimate a spectrophotometric distance of 18.1 ± 3.7 parsecs (59 ± 12 ly) from combined SDSS iz-band and 2MASS JHK-band photometry[3] whereas Buenzli et al. (2014) estimate a spectrophotometric distance of 20.3 ± 3.0 parsecs (66.2 ± 9.8 ly) from 2MASS H-band photometry.[4]

Proper motion

2MASS J1219+3128 has a net proper motion of 238.2 mas/yr with position angle 257.98 degrees,[lower-alpha 1][lower-alpha 2] indicating motion in south-west direction on the sky.[3]

See also

The other two discoveries of rapidly-rotating brown dwarfs, presented in Tannock et al. (2021):[2]

Notes
  1. The net proper motion is given by:  mas/yr, where and are the components of proper motion in the RA and Dec, respectively.
  2. The position angle of proper motion is given by

References
  1. "2MASS J12195156+3128497 -- Brown Dwarf (M<0.08solMass)". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 4 March 2021.
  2. Tannock, Megan E.; Metchev, Stanimir; Heinze, Aren; Miles-Páez, Paulo A.; Gagné, Jonathan; Burgasser, Adam; et al. (March 2021). "Weather on Other Worlds. V. The Three Most Rapidly Rotating Ultra-cool Dwarfs". The Astronomical Journal. 161 (5): 224. arXiv:2103.01990. Bibcode:2021AJ....161..224T. doi:10.3847/1538-3881/abeb67. S2CID 232105126.
  3. Schmidt, Sarah J.; West, Andrew A.; Hawley, Suzanne L.; Pineda, J. Sebastian (May 2010). "Colors and Kinematics of L Dwarfs from the Sloan Digital Sky Survey". The Astronomical Journal. 139 (5): 1808–1821. arXiv:1001.3402. Bibcode:2010AJ....139.1808S. doi:10.1088/0004-6256/139/5/1808. S2CID 190648.
  4. Buenzli, Esther; Apai, Dániel; Radigan, Jacqueline; Reid, I. Neill; Flateau, Davin (February 2014). "Brown Dwarf Photospheres are Patchy: A Hubble Space Telescope Near-infrared Spectroscopic Survey Finds Frequent Low-level Variability". The Astronomical Journal. 782 (2): 18. arXiv:1312.5294. Bibcode:2014ApJ...782...77B. doi:10.1088/0004-637X/782/2/77. S2CID 118492708. 77.
  5. Cofield, Calla (7 April 2021). "Trio of Fast-Spinning Brown Dwarfs May Reveal a Rotational Speed Limit". Jet Propulsion Laboratory. NASA. Retrieved 7 April 2021.
  6. Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  7. Chiu, K.; Fan, X.; Leggett, S. K.; Golimowski, D. A.; Zheng, W.; Schneider, D. P.; Brinkmann, J. (June 2006). "Seventy-One New L and T Dwarfs from the Sloan Digital Sky Survey" (PDF). The Astronomical Journal. 131 (5): 2722–2736. arXiv:astro-ph/0601089. Bibcode:2006AJ....131.2722C. doi:10.1086/501431. S2CID 119095669.
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