LP 944-20

Coordinates: 03^h 39^m 35.22^s, −35° 25′ 44.09″

LP 944-20

Observation data Epoch J2000      Equinox J2000
Constellation	Fornax
Right ascension	03^h 39^m 35.220^s[1]
Declination	–35° 25′ 44.09″[1]
Apparent magnitude (V)	18.69[2]
Characteristics
Spectral type	M9[1]
Apparent magnitude (B)	~20.17[1]
Apparent magnitude (I)	~13.288[1]
Apparent magnitude (J)	10.725±0.021[1]
Apparent magnitude (H)	10.017±0.021[1]
Apparent magnitude (K)	9.548±0.023[1]
Astrometry
Proper motion (μ)	RA: 317±60[1] mas/yr Dec.: 276±52[1] mas/yr
Parallax (π)	155.89 ± 1.03[3][4] mas
Distance	20.9 ± 0.1 ly (6.41 ± 0.04 pc)
Absolute magnitude (MV)	20.02
Details
Mass	0.07[2] M☉
Other designations
LP 944-20, SIPS J0339−3525, LEHPM 3451, 2MASSI J0339352−352544, [B2006] J033935.2−352544, APMPM J0340−3526, 2MASS J03393521−3525440, 2MASSW J0339352−352544, BRI B0337−3535, BRI 0337−3535, 2MUCD 10201
Database references
SIMBAD	data

LP 944-20 is a dim brown dwarf of spectral class M9 located about 21 light-years from the Solar System in the constellation of Fornax. With a visual apparent magnitude of 18,^[2] it has one of the dimmest visual magnitudes listed on the RECONS page.

On 15 December 1999 a flare was detected.^[5]

Distance

The first parallax measurement from 1996 found that LP 944-20 (designated there as BRI 0337−3535) has a relative parallax of $\pi _{r}=200.0\pm 4.2$ mas, and its correction from relative to absolute parallax (i.e. mean parallax of the reference frame stars) is $\pi _{{ref}}=1.4\pm 0.3$ mas. This yields an absolute parallax of $\pi _{r}+\pi _{{ref}}=200.0+1.4=201.4$ mas, with a standard deviation (according to $\sigma _{{X+Y}}^{2}=\sigma _{X}^{2}+\sigma _{Y}^{2}$^[6]) of ${\sqrt {\sigma _{{\pi _{r}}}^{2}+\sigma _{{\pi _{{ref}}}}^{2}}}={\sqrt {4.2^{2}+0.3^{2}}}=4.21$ mas, which corresponds to a distance of 5±0.1 pc, or 16.2±0.3 ly.^[7] (The same values of absolute parallax and its standard deviation are in the RECONS' TOP100 list.^{[2][note 1]}

A newer parallax, published in 2013, is 155.89±1.03 mas (6.41±0.04 pc or 20.92±0.14 ly).^[3]

Lithium and clouds

Observations published in 2007 showed that the atmosphere of LP 944-20 contains much lithium and that it has dusty clouds.^[8]

Notes

1. In RECONS' TOP100 older versions the standard deviation value was 4.20 mas, not 4.21 mas.

References

1. "SIPS J0339-3525 -- Brown Dwarf (M<0.08solMass)". Centre de Données astronomiques de Strasbourg. Retrieved 2009-12-14.
2. Research Consortium on Nearby Stars, Georgia State University (January 1, 2012). "The 100 nearest star systems". RECONS. Retrieved 2012-06-11. External link in |journal= (help)
3. Dieterich, Sergio B.; Todd J. Henry; Wei-Chun Jao; Jennifer G. Winters; Altonio D. Hosey (2013). "The Solar Neighborhood XXXII: The Hydrogen Burning Limit". arXiv:1312.1736v1.
4. Lurie, John C.; Henry, Todd J.; Jao, Wei-Chun; Quinn, Samuel N.; Winters, Jennifer G.; Ianna, Philip A.; Koerner, David W.; Riedel, Adric R.; Subasavage, John P. (2014). "The Solar Neighborhood. XXXIV. a Search for Planets Orbiting Nearby M Dwarfs Using Astrometry". The Astronomical Journal. 148 (5): 91. arXiv:1407.4820. Bibcode:2014AJ....148...91L. doi:10.1088/0004-6256/148/5/91.
5. http://www.solstation.com/stars/lp944-20.jpg
6. Mean and Variance of Random Variables
7. Tinney, C. G. (1996). "CCD astrometry of southern very low-mass stars". Monthly Notices of the Royal Astronomical Society. 281 (2): 644–658. Bibcode:1996MNRAS.281..644T. doi:10.1093/mnras/281.2.644.
8. Pavlenko, Ya. V.; et al. (September 2007). "Lithium in LP944-20". Monthly Notices of the Royal Astronomical Society. 380 (3): 1285–1296. arXiv:0707.0694. Bibcode:2007MNRAS.380.1285P. doi:10.1111/j.1365-2966.2007.12182.x.

External links

• "The 100 nearest star systems", Research Consortium on Nearby Stars