Ross 154

Coordinates: Sky map 18h 49m 49.3625s, −23° 50′ 10.437″
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Ross 154
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 49m 49.36216s[1]
Declination –23° 50′ 10.4291″[1]
Apparent magnitude (V) 10.44[2]
Characteristics
Spectral type M3.5V[2]
B−V color index 1.76[3]
Variable type Flare star[4]
Astrometry
Radial velocity (Rv)–10.7[5] km/s
Proper motion (μ) RA: +637.02[1] mas/yr
Dec.: –191.64[1] mas/yr
Parallax (π)336.72 ± 2.03 mas[1]
Distance9.69 ± 0.06 ly
(2.97 ± 0.02 pc)
Absolute magnitude (MV)13.07[2]
Details
Mass0.17[2] M☉
Radius0.24[6] R☉
Luminosity0.0038[7] L☉
Surface gravity (log g)5.00 ± 0.05[8] cgs
Temperature3,340 ± 10[8] K
Metallicity [Fe/H]-0.25[9] dex
Rotational velocity (v sin i)3.5 ± 1.5[9] km/s
Ageunder 1[9] Gyr
Other designations
AC-24 2833-183, GCTP 4338, GJ 729, HIP 92403, LHS 3414, V1216 Sagittarii.[10]

Ross 154 (V1216 Sgr) is a star in the southern zodiac constellation of Sagittarius. It has an apparent visual magnitude of 10.44,[2] making it much too faint to be seen with the naked eye. At a minimum, viewing Ross 154 requires a telescope with an aperture of 6.5 cm (3 in) under ideal conditions.[11] The distance to this star can be estimated from parallax measurements, which places it at 9.69 light-years (2.97 parsecs) away from Earth.[1] It is the nearest star in the southern constellation Sagittarius, and one of the closest to the Sun.

This star was first catalogued by American astronomer Frank Elmore Ross in 1925, and formed part of his fourth list of new variable stars.[12] In 1926, he added it to his second list of stars showing a measurable proper motion after comparing its position with photographic plates taken earlier by fellow American astronomer E. E. Barnard.[13] A preliminary parallax value of 0.362 ± 0.006 arcseconds was determined in 1937 by Walter O'Connell using photographic plates from the Yale telescope in Johannesburg, South Africa. This placed the star at the sixth position of the then-known nearby stars.[14]

Ross 154 was found to be a UV Ceti-type flare star, with a mean time between major flares of about two days.[4] The first such flare activity was observed from Australia in 1951 when the star increased in magnitude by 0.4.[15] Typically, the star will increase by 3–4 magnitudes during a flare.[16] The strength of the star's surface magnetic field is an estimated 2.2 ± 0.1 kG.[17] Ross 154 is an X-ray source and it has been detected by several X-ray observatories. The quiescent X-ray luminosity is about 9 × 1027 ergs s−1.[9] X-ray flare emission from this star has been observed by Chandra observatory, with a particularly large flare emitting 2.3 × 1033 erg.[9]

A stellar classification of M3.5V[2] makes this a red dwarf star that is generating energy through the nuclear fusion of hydrogen at its core. It has an estimated 17% of the Sun's mass[2] and 24% of the Sun's radius,[6] but it is radiating only 0.38% of the luminosity of the Sun.[7] In contrast to the Sun where convection only occurs in the outer layers, a red dwarf with a mass this low will be entirely convective.[18] Based on the relatively high projected rotation, this is probably a young star with an estimated age of less than a billion years.[9] The abundance of elements heavier than helium is about half that in the Sun.[9]

No low-mass companions have been discovered in orbit around Ross 154.[19] Nor does it display the level of excess infrared emission that would suggest the presence of circumstellar dust. Such debris disks are rare among M-type star systems older than about 10 million years, having been primarily cleared away by drag from the stellar wind.[20] The space velocity components of this star in the galactic coordinate system are [U, V, W] = [–12.2, –1.0, –7.2] km s–1.[21] It has not been identified as a member of a specific stellar moving group[22] and is orbiting through the Milky Way galaxy at a distance from the core that varies from 27.65–30.66 kly (8.48–9.40 kpc) with an orbital eccentricity of 0.052.[23] Based on its low velocity relative to the Sun, this is believed to be a young disk (Population I) star.[24] This star will make its closest approach to the Sun in about 157,000 years, when it comes within 6.39 ± 0.10 ly (1.959 ± 0.031 pc).[25]

See also

References

  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 {{citation}}: Unknown parameter |month= ignored (help)
  2. ^ a b c d e f g Staff (January 1, 2008), The One Hundred Nearest Star Systems, Research Consortium on Nearby Stars, retrieved 2008-06-12
  3. ^ Corben, P. M.; et al. (1972), "U, B, V photometry of 500 southern stars", Monthly Notes of the Astronomical Society of South Africa, 31: 7–22, Bibcode:1972MNSSA..31....8C
  4. ^ a b Jarrett, A. H. (1976), "On the Period Between Flares of V1216 Sagittarii", Information Bulletin on Variable Stars (1221): 1, Bibcode:1976IBVS.1221....1J {{citation}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  5. ^ Gontcharov, G. A. (2006), Pulkovo Compilation of Radial Velocities for 35493 Hipparcos Stars, retrieved 2010-04-18
  6. ^ a b Johnson, H. M.; Wright, C. D. (1983), "Predicted infrared brightness of stars within 25 parsecs of the sun", Astrophysical Journal Supplement Series, 53: 643–711, Bibcode:1983ApJS...53..643J, doi:10.1086/190905—see p. 693.
  7. ^ a b Pettersen, B. R. (1980), "Physical parameters of solar neighbourhood flare stars", Astronomy and Astrophysics, 82 (1–2): 53–60, Bibcode:1980A&A....82...53P
  8. ^ a b Mentuch, Erin; et al., "Lithium Depletion of Nearby Young Stellar Associations", The Astrophysical Journal, 689 (2): 1127–1140, arXiv:0808.3584, Bibcode:2008ApJ...689.1127M, doi:10.1086/592764
  9. ^ a b c d e f g Wargelin, B. J.; et al. (2008), "X-Ray Flaring on the dMe Star, Ross 154", The Astrophysical Journal, 676 (1): 610–627, arXiv:0712.2791, Bibcode:2008ApJ...676..610W, doi:10.1086/528702
  10. ^ "V* V1216 Sgr -- Flare Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2008-06-12
  11. ^ Mills, H. Robert (1994), Practical Astronomy: A User-friendly Handbook for Skywatchers, Horwood Publishing, p. 199, ISBN 1-898563-02-0
  12. ^ Ross, Frank E. (1926), "New variable stars, (fourth list)", Astronomical Journal, 37: 91, Bibcode:1927AJ.....37...91R, doi:10.1086/104790
  13. ^ Ross, Frank E. (1926), "New proper-motion stars, (second list)", Astronomical Journal, 36 (856): 124–128, Bibcode:1926AJ.....36..124R, doi:10.1086/104699 {{citation}}: Unknown parameter |month= ignored (help)
  14. ^ O'Connell, Walter (1938), "A faint star of large parallax", Astronomical Journal, 46 (1078): 204, Bibcode:1938AJ.....46..204O, doi:10.1086/105447 {{citation}}: Unknown parameter |month= ignored (help)
  15. ^ Mayall, Margaret W. (1953), "Variable Star Notes", Journal of the Royal Astronomical Society of Canada, 47: 23–28, Bibcode:1953JRASC..47...23M {{citation}}: Unknown parameter |month= ignored (help)
  16. ^ Costa, R.; Cristaldi, S.; Rodono, M. (1970), "Cooperative Observations of the Flare Star V1216 Sgr", Information Bulletin on Variable Stars, 461: 1–4, Bibcode:1970IBVS..461....1C
  17. ^ Reiners, A.; Basri, G. (2007), "The First Direct Measurements of Surface Magnetic Fields on Very Low Mass Stars", The Astrophysical Journal, 656 (2): 1121–1135, arXiv:astro-ph/0610365, Bibcode:2007ApJ...656.1121R, doi:10.1086/510304 {{citation}}: Unknown parameter |month= ignored (help)
  18. ^ Reiners, A.; Basri, G. (2009), "On the magnetic topology of partially and fully convective stars", Astronomy and Astrophysics, 496 (3): 787–790, arXiv:0901.1659, Bibcode:2009A&A...496..787R, doi:10.1051/0004-6361:200811450 {{citation}}: Unknown parameter |month= ignored (help)
  19. ^ Hinz, Joannah L.; et al. (2002), "A Near-Infrared Wide-Field Proper Motion Search for Brown Dwarfs", The Astronomical Journal, 123 (4): 2027–2032, arXiv:astro-ph/0201140, Bibcode:2002AJ....123.2027H, doi:10.1086/339555{{citation}}: CS1 maint: multiple names: authors list (link)
  20. ^ Plavchan, Peter; Jura, M.; Lipscy, S. J. (2005), "Where Are the M Dwarf Disks Older Than 10 Million Years?", The Astrophysical Journal, 631 (2): 1161–1169, arXiv:astro-ph/0506132, Bibcode:2005ApJ...631.1161P, doi:10.1086/432568 {{citation}}: Unknown parameter |month= ignored (help)
  21. ^ "Annotations on V* V1216 Sgr object". SIMBAD. Retrieved 2010-04-18.
  22. ^ Montes, D.; et al. (2001), "Late-type members of young stellar kinematic groups - I. Single stars", Monthly Notices of the Royal Astronomical Society, 328 (1): 45–63, arXiv:astro-ph/0106537, Bibcode:2001MNRAS.328...45M, doi:10.1046/j.1365-8711.2001.04781.x
  23. ^ Allen, C.; Herrera, M. A. (1998), "The galactic orbits of nearby UV Ceti stars", Revista Mexicana de Astronomia y Astrofisica, 34: 37–46, Bibcode:1998larm.confE.115A
  24. ^ Veeder, G. J. (1974), "Old disk flare stars", Astronomical Journal, 79: 702–704, Bibcode:1974AJ.....79..702V, doi:10.1086/111600
  25. ^ Bobylev, V. V. (2010), "Searching for stars closely encountering with the solar system", Astronomy Letters, 36 (3): 220–226, arXiv:1003.2160, Bibcode:2010AstL...36..220B, doi:10.1134/S1063773710030060 {{citation}}: Unknown parameter |month= ignored (help)

External links


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