Ross 154

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Ross 154[1]
Observation data
Epoch J2000
Constellation
(pronunciation)		 Sagittarius
Right ascension 18h 49m 49.3625s
Declination −23° 50′ 10.437″
Apparent magnitude (V) 10.95
Characteristics
Spectral type M3.5V
B-V color index 1.76[2]
Variable type Flare star
Astrometry
Radial velocity (Rv) −4.0 km/s
Proper motion (μ) RA: 637.57 mas/yr
Dec.: −192.47 mas/yr
Parallax (π) 336.48 ± 1.82[3] mas
Distance 9.69 ± 0.05 ly
(2.97 ± 0.02 pc)
Absolute magnitude (MV) 13.07[4]
Details
Mass 0.17[4] M☉
Radius 0.24[5] R☉
Luminosity 0.0038[6] L☉
Temperature 3,105[5] K
Metallicity \begin{smallmatrix}\left[ \frac{Fe}{H} \right] \approx -0.25\end{smallmatrix}[7]
Rotation v sin i = 3.5±1.5 km/s[7]
Age under 109[7] years
Other designations
GCTP 4338, GJ 729, LHS 3414, V1216 Sagittarii, AC-24 2833-183, HIP 92403.

Ross 154 (V1216 Sgr) is a red dwarf star approximately 3.0 pc or 9.68 light years from the Sun. It is the nearest star in the southern constellation Sagittarius, and one of the closest to the Sun. Its nearest neighbor is Barnard's star, located 1.66 pc (5.41 ly) away.

This star was first catalogued by Frank Elmore Ross in 1925, and formed part of his fourth list of new variable stars.[8] It was found to be a UV Ceti-type flare star, with a mean time between major flares of about two days.[9] Typically, the star will increase by 3–4 magnitudes during a flare.[10] However, at 11th magnitude, this star is much too faint to be viewed with the unaided eye and requires at least a 65 mm telescope aperture to be seen under ideal conditions.[11]

Ross 154 has an estimated 17% of the Sun's mass[4] and is only 24% of the Sun's radius.[5] Based on the relatively high projected rotation, this is probably a young star with an estimated age of less than a billion years. The abundance of elements heavier than helium is about half that of the Sun. The strength of the star's magnetic field is an estimated 2.6±0.3 kG. This star is an X-ray source and it has been detected by several X-ray observatories. X-ray flare emission from Ross 154 has been observed by Chandra observatory.[7]

The space velocity components of this star are U = –9, V = 0 and W = -8 km/s. It has not been identified as a member of a specific stellar moving group.[12] It is orbiting through the Milky Way galaxy at a distance from the core that varies from 8.478–9.400 kpc and an orbital eccentricity of 0.052.[13] Based on its low velocity relative to the Sun, this is believed to be a young disk (Population I) star.[14] It is predicted that this star will make its closest approach to the Sun in 150,000 years, when it comes within 1.88 ± 0.08 pc (6.13 ly).[15]

No low-mass companions have been discovered in orbit around this star.[16]

[edit] See also

[edit] References

  1. ^ V* V1216 Sgr -- Flare Star. Centre de Données astronomiques de Strasbourg. Retrieved on 2008-06-12.
  2. ^ 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. 
  3. ^ Perryman, M. A. C.; et al (1997). "The Hipparcos Catalogue". Astronomy & Astrophysics 323: L49–L52. 
  4. ^ a b c Staff (January 1, 2008). The One Hundred Nearest Star Systems. Research Consortium on Nearby Stars. Retrieved on 2008-06-12.
  5. ^ a b c 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. —see p. 693.
  6. ^ Pettersen, B. R. (1980). "Physical parameters of solar neighbourhood flare stars". Astronomy and Astrophysics 82 (1–2): 53–60. 
  7. ^ a b c d Wargelin, B. J.; Kashyap, V. L.; Drake, J. J.; García-Alvarez, D.; Ratzlaff, P. W. (2008). "X-Ray Flaring on the dMe Star, Ross 154". The Astrophysical Journal 676 (1): 610–627. 
  8. ^ Ross, Frank E. (1926). "New variable stars, (fourth list)". Astronomical Journal 37: 91. 
  9. ^ Jarrett, A. H.; Grabner, G. (1976). "On the Period Between Flares of V1216 Sagittarii". Information Bulletin on Variable Stars, (1221): 1. 
  10. ^ Costa, R.; Cristaldi, S.; Rodono, M. (1970). "Cooperative Observations of the Flare Star V1216 Sgr". Information Bulletin on Variable Stars 461: 1–4. 
  11. ^ Mills, H. Robert (1994). Practical Astronomy: A User-friendly. Horwood Publishing, 199. ISBN 1898563020. 
  12. ^ Montes, D.; López-Santiago, J.; Gálvez, M. C.; Fernández-Figueroa, M. J.; De Castro, E.; Cornide, M. (2001). "Late-type members of young stellar kinematic groups - I. Single stars". Monthly Notices of the Royal Astronomical Society 328 (1): 45–63. 
  13. ^ Allen, C.; Herrera, M. A. (1998). "The galactic orbits of nearby UV Ceti stars". Revista Mexicana de Astronomia y Astrofisica 34: 37–46. 
  14. ^ Veeder, G. J. (1974). "Old disk flare stars". Astronomical Journal 79: 702–704. 
  15. ^ García-Sánchez, J.; Weissman, P. R.; Preston, R. A.; Jones, D. L.; Lestrade, J.-F.; Latham, D. W.; Stefanik, R. P.; Paredes, J. M. (2001). "Stellar encounters with the solar system". Astronomy and Astrophysics 379: 634–659. 
  16. ^ Hinz, Joannah L.; McCarthy, Donald W., Jr.; Simons, Doug A.; Henry, Todd J.; Kirkpatrick, J. Davy; McGuire, Patrick C. (2002). "A Near-Infrared Wide-Field Proper Motion Search for Brown Dwarfs". The Astronomical Journal 123 (4): 2027–2032. 

[edit] External links