LP 944-20

LP 944-20

LP 944-20 Credit: legacy surveys
Observation data Epoch J2000      Equinox J2000
Constellation	Fornax
Right ascension	03^h 39^m 35.252^s[1]
Declination	–35° 25′ 43.64″[1]
Apparent magnitude (V)	18.69
Characteristics
Spectral type	M9β[2]
Apparent magnitude (g)	19.7263±0.0083[3]
Apparent magnitude (r)	17.1191±0.0010[3]
Apparent magnitude (i)	16.8189±0.0014[3]
Apparent magnitude (z)	15.6215±0.0011[3]
Apparent magnitude (Y)	14.5973±0.0014[3]
Apparent magnitude (J)	10.725±0.021[4]
Apparent magnitude (H)	10.017±0.021[4]
Apparent magnitude (K)	9.548±0.023[4]
Astrometry
Radial velocity (Rv)	7.43±0.72[2] km/s
Proper motion (μ)	RA: 309.001(50) mas/yr[1] Dec.: 269.058(64) mas/yr[1]
Parallax (π)	155.5982 ± 0.0522 mas[1]
Distance	20.961 ± 0.007 ly (6.427 ± 0.002 pc)
Absolute magnitude (MV)	20.02
Details[5]
Mass	29.62±16.67[2] MJup
Temperature	2,650 ± 30 K (2,376.8 ± 30.0 °C; 4,310.3 ± 54.0 °F) K
Rotation	3.8291±0.0084 h[6]
Rotational velocity (v sin i)	28±4 km/s
Age	320 ±80 million years
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, Gaia DR2 4860376345833699840
Database references
SIMBAD	data
LP 944-20 Location of LP 944-20 in the constellation Fornax

LP 944-20 is a dim brown dwarf of spectral class M9 located 21 light-years from the Solar System in the constellation of Fornax. With a visual apparent magnitude of 18.69, it has one of the dimmest visual magnitudes listed on the RECONS page. It is one of the brightest brown dwarfs, if not the brightest at J_MKO=10.68±0.03 mag.^[7]

Discovery

LP 944-20 was discovered in the Luyten-Palomar Survey. It appears as a star with R=17.5 mag with a proper motion of 334 mas/yr in a catalog from 1979.^[8] It was however first published in 1975 by Luyten & Kowal.^[9][10] It was re-discovered in the APM survey, a quasar survey, in which the red color was noticed. The first spectrum was published in 1997 by Kirkpatrick, Henry & Irwin. A spectral type of M9 or later was assigned in this work and a distance of around 5 parsec was established thanks to the parallax being measured.^[10] In 1998 Tinney discovered that this M-dwarf shows the 6708 Å Lithium absorption line and H-alpha emission line, which helped to constrain the age to around 500 million years and established it as a brown dwarf with a mass of around 60 M_J.^[11]

Physical characteristics

Short after LP 944-20 was established as a brown dwarf, the fast rotation was detected in 1998.^[12] Later a work in 1999 claimed to have detected variability in LP 944-20.^[13] A search for dust around LP 944-20 has shown that it has no disk.^[14]

Due to short rotational period, this young brown dwarf is displaying strong and frequent X-ray flares, and possessing a strong magnetic field reaching 135 G at the photosphere level.^[5] On 15 December 1999, an X-ray flare was detected.^[15][16] On 27 July 2000, radio emission (in flare and quiescence) was detected from this brown dwarf by a team of students at the Very Large Array.^[17]

Observations published in 2007 showed that the atmosphere of LP 944-20 contains much lithium and that it has dusty clouds.^[18] A search for planets was carried out in 2006 using the radial velocity method. No planets were found, but variability with an amplitude of 3.5 km/s was detected. This variability is likely due to weather effects and the rotation of the brown dwarf.^[19]

In 2015 high resolution Doppler images were taken of LP 944-20 and GJ 791.2A. The time series spectra show line profile distortions, which were interpreted as starspots. These starspots were reconstructed and found to be concentrated at high latitudes. The modelling produces a better fit of ΔT=200 K (−73 °C; −100 °F) between starspots (T_spot=2,100 K (1,830 °C; 3,320 °F)) and photosphere (T_phot=2,300 K (2,030 °C; 3,680 °F)).^[20]

In a large program in 2016 the spectral type was established to be M9β in the optical and L0β in the infrared. The beta stands for a surface gravity intermediate between normal and low. The mass was calculated to be 29.62±16.67 M_J.^[2]

Observations with TESS found that LP 944-20 is variable with a period of around 3.8 hours and an amplitude of 1760±100 ppm.^[6] This is in agreement with previous estimates of a period of less than 4.5 hours.^[5]

References

1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
2. Faherty, Jacqueline K.; Riedel, Adric R.; Cruz, Kelle L.; Gagne, Jonathan; Filippazzo, Joseph C.; Lambrides, Erini; Fica, Haley; Weinberger, Alycia; Thorstensen, John R.; Tinney, C. G.; Baldassare, Vivienne; Lemonier, Emily; Rice, Emily L. (2016-07-01). "Population Properties of Brown Dwarf Analogs to Exoplanets". The Astrophysical Journal Supplement Series. 225 (1): 10. arXiv:1605.07927. Bibcode:2016ApJS..225...10F. doi:10.3847/0067-0049/225/1/10. ISSN 0067-0049.
3. Abbott, T. M. C.; Adamów, M.; Aguena, M.; Allam, S.; Amon, A.; Annis, J.; Avila, S.; Bacon, D.; Banerji, M.; Bechtol, K.; Becker, M. R.; Bernstein, G. M.; Bertin, E.; Bhargava, S.; Bridle, S. L. (2021-08-01). "The Dark Energy Survey Data Release 2". The Astrophysical Journal Supplement Series. 255 (2): 20. arXiv:2101.05765. Bibcode:2021ApJS..255...20A. doi:10.3847/1538-4365/ac00b3. ISSN 0067-0049.
4. "SIPS J0339-3525 -- Brown Dwarf (M<0.08solMass)". Centre de Données astronomiques de Strasbourg. Retrieved 2009-12-14.
5. Guenther, E. W.; Zapatero-Osorio, María Rosa; Mehner, A.; Martín, Eduardo L. (2009), "Short-term spectroscopic monitoring of two cool dwarfs with strong magnetic fields", Astronomy & Astrophysics, 498 (1): 281–287, arXiv:0903.2340, Bibcode:2009A&A...498..281G, doi:10.1051/0004-6361/200810216, S2CID 18611224
6. Fetherolf, Tara; Pepper, Joshua; Simpson, Emilie; Kane, Stephen R.; Močnik, Teo; English, John Edward; Antoci, Victoria; Huber, Daniel; Jenkins, Jon M.; Stassun, Keivan; Twicken, Joseph D.; Vanderspek, Roland; Winn, Joshua N. (2023-09-01). "Variability Catalog of Stars Observed during the TESS Prime Mission". The Astrophysical Journal Supplement Series. 268 (1): 4. arXiv:2208.11721. Bibcode:2023ApJS..268....4F. doi:10.3847/1538-4365/acdee5. ISSN 0067-0049.
7. Sanghi, Aniket; Liu, Michael C.; Best, William M. J.; Dupuy, Trent J.; Siverd, Robert J.; Zhang, Zhoujian; Hurt, Spencer A.; Magnier, Eugene A.; Aller, Kimberly M.; Deacon, Niall R. (2023). "Table of Ultracool Fundamental Properties". Zenodo. doi:10.5281/zenodo.10086810.
8. "NLTT Catalogue (Luyten, 1979) VizieR". vizier.cds.unistra.fr. 1979. Retrieved 2024-03-09.
9. Luyten, W. J.; Kowal, C. T. (1975-01-01). "Proper motion survey with the forty-eight inch Schmidt telescope. XLIII. One hundred and six faint stars with large proper motions". Proper Motion Survey, University of Minnesota. 43: 1. Bibcode:1975PMMin..43....1L.
10. Kirkpatrick, J. Davy; Henry, Todd J.; Irwin, Michael J. (1997-04-01). "Ultra-Cool M Dwarfs Discovered by QSO Surveys.I: The APM Objects". The Astronomical Journal. 113: 1421–1428. Bibcode:1997AJ....113.1421K. doi:10.1086/118357. ISSN 0004-6256.
11. Tinney, C. G. (1998-06-01). "The intermediate-age brown dwarf LP944-20". Monthly Notices of the Royal Astronomical Society. 296 (4): L42 – L44. arXiv:astro-ph/9801171. Bibcode:1998MNRAS.296L..42T. doi:10.1046/j.1365-8711.1998.01642.x. ISSN 0035-8711.
12. Tinney, C. G.; Reid, I. N. (1998-12-01). "High-resolution spectra of very low-mass stars". Monthly Notices of the Royal Astronomical Society. 301 (4): 1031–1048. arXiv:astro-ph/9806004. Bibcode:1998MNRAS.301.1031T. doi:10.1046/j.1365-8711.1998.02079.x. ISSN 0035-8711.
13. Tinney, C. G.; Tolley, A. J. (1999-03-01). "Searching for weather in brown dwarfs". Monthly Notices of the Royal Astronomical Society. 304 (1): 119–126. arXiv:astro-ph/9809165. Bibcode:1999MNRAS.304..119T. doi:10.1046/j.1365-8711.1999.02297.x. ISSN 0035-8711.
14. Apai, Dániel; Pascucci, Ilaria; Henning, Thomas; Sterzik, Michael F.; Klein, Randolf; Semenov, Dimitri; Guenther, Eike; Stecklum, Bringfried (2003-06-01). "Probing Dust around Brown Dwarfs: The Naked LP 944-20 and the Disk of Cha Hα2". Brown Dwarfs, Proceedings of IAU Symposium #211. 211: 137. Bibcode:2003IAUS..211..137A.
15. Rutledge, Robert E.; Basri, Gibor; Martín, Eduardo L.; Bildsten, Lars (1 August 2000). "Chandra Detection of an X-Ray Flare from the Brown Dwarf LP 944-20". The Astrophysical Journal. 538 (2): L141 – L144. arXiv:astro-ph/0005559. Bibcode:2000ApJ...538L.141R. doi:10.1086/312817. S2CID 17800872.
16. "LP 944-20". Solstation.com. Retrieved 2017-03-11.
17. Berger, E.; Ball, S.; Becker, K. M.; Clarke, M.; Frail, D. A.; Fukuda, T. A.; Hoffman, I. M.; Mellon, R.; Momjian, E.; Murphy, N. W.; Teng, S. H.; Woodruff, T.; Zauderer, B. A.; Zavala, R. T. (2001-03-15). "Discovery of radio emission from the brown dwarf LP944-20". Nature. 410 (6826): 338–340. arXiv:astro-ph/0102301. Bibcode:2001Natur.410..338B. doi:10.1038/35066514. PMID 11268202. S2CID 4411256.
18. Pavlenko, Ya. V.; Jones, H. R. A.; Martín, Eduardo L.; Guenther, E.; Kenworthy, M. A.; Zapatero-Osorio, María Rosa (September 2007). "Lithium in LP944-20". Monthly Notices of the Royal Astronomical Society. 380 (3): 1285–96. arXiv:0707.0694. Bibcode:2007MNRAS.380.1285P. doi:10.1111/j.1365-2966.2007.12182.x. S2CID 11186385.
19. Martín, E. L.; Guenther, E.; Zapatero Osorio, M. R.; Bouy, H.; Wainscoat, R. (2006-06-01). "A Multiwavelength Radial Velocity Search for Planets around the Brown Dwarf LP 944-20". The Astrophysical Journal. 644 (1): L75 – L78. arXiv:astro-ph/0605263. Bibcode:2006ApJ...644L..75M. doi:10.1086/505343. ISSN 0004-637X.
20. Barnes, J. R.; Jeffers, S. V.; Jones, H. R. A.; Pavlenko, Ya. V.; Jenkins, J. S.; Haswell, C. A.; Lohr, M. E. (2015-10-01). "Starspot Distributions on Fully Convective M Dwarfs: Implications for Radial Velocity Planet Searches". The Astrophysical Journal. 812 (1): 42. arXiv:1509.05284. Bibcode:2015ApJ...812...42B. doi:10.1088/0004-637X/812/1/42. ISSN 0004-637X. S2CID 14907824.

External links

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