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Ross 154

Coordinates: Sky map 18h 49m 49.3625s, −23° 50′ 10.437″
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Ross 154[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 49m 49.36s [2]
Declination –23° 50′ 10.4″ [2]
Apparent magnitude (V) 10.95
Characteristics
Spectral type M3.5V
B−V color index 1.76[3]
Variable type Flare star
Astrometry
Radial velocity (Rv)–10.7[4] km/s
Proper motion (μ) RA: 637.02 ± 2.80 [2] mas/yr
Dec.: –191.64 ± 1.70 [2] mas/yr
Parallax (π)336.72 ± 2.03 mas[2]
Distance9.69 ± 0.06 ly
(2.97 ± 0.02 pc)
Absolute magnitude (MV)13.07[5]
Details
Mass0.17[5] M☉
Radius0.24[6] R☉
Luminosity0.0038[7] L☉
Temperature3,105[6] K
Metallicity[8]
Rotational velocity (v sin i)3.5±1.5 [8] km/s
Ageunder 109[8] 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.[9] It was found to be a UV Ceti-type flare star, with a mean time between major flares of about two days.[10] Typically, the star will increase by 3–4 magnitudes during a flare.[11] 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.[12]

Ross 154 has an estimated 17% of the Sun's mass[5] and is only 24% of the Sun's radius.[6] 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.[8]

The space velocity components of this star are U = –12.2, V = -1.0 and W = -7.2 km/s.[13] It has not been identified as a member of a specific stellar moving group.[14] 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.[15] Based on its low velocity relative to the Sun, this is believed to be a young disk (Population I) star.[16] 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).[17]

No low-mass companions have been discovered in orbit around this star.[18]

See also

References

  1. ^ "V* V1216 Sgr -- Flare Star". Centre de Données astronomiques de Strasbourg. Retrieved 2008-06-12.
  2. ^ a b c d e van Leeuwen, F. (2007). "HIP 92403". Hipparcos, the New Reduction. Retrieved 2009-12-13.
  3. ^ Corben, P. M. (1972). "U, B, V photometry of 500 southern stars". Monthly Notes of the Astronomical Society of South Africa. 31: 7–22. Retrieved 2008-06-12. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35493 Hipparcos Stars". Retrieved 2010-04-18.
  5. ^ a b c Staff (January 1, 2008). "The One Hundred Nearest Star Systems". Research Consortium on Nearby Stars. Retrieved 2008-06-12.
  6. ^ a b c Johnson, H. M. (1983). "Predicted infrared brightness of stars within 25 parsecs of the sun". Astrophysical Journal Supplement Series. 53: 643–711. doi:10.1086/190905. Retrieved 2008-06-12. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)—see p. 693.
  7. ^ Pettersen, B. R. (1980). "Physical parameters of solar neighbourhood flare stars". Astronomy and Astrophysics. 82 (1–2): 53–60. Retrieved 2008-06-13.
  8. ^ a b c d Wargelin, B. J. (2008). "X-Ray Flaring on the dMe Star, Ross 154". The Astrophysical Journal. 676 (1): 610–627. doi:10.1086/528702. Retrieved 2010-03-21. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  9. ^ Ross, Frank E. (1926). "New variable stars, (fourth list)". Astronomical Journal. 37: 91. doi:10.1086/104790. Retrieved 2008-06-13.
  10. ^ Jarrett, A. H. (1976). "On the Period Between Flares of V1216 Sagittarii". Information Bulletin on Variable Stars, (1221): 1. Retrieved 2008-06-13. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: extra punctuation (link)
  11. ^ Costa, R. (1970). "Cooperative Observations of the Flare Star V1216 Sgr". Information Bulletin on Variable Stars. 461: 1–4. Retrieved 2008-06-13. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  12. ^ Mills, H. Robert (1994). Practical Astronomy: A User-friendly. Horwood Publishing. p. 199. ISBN 1898563020.
  13. ^ "Annotations on V* V1216 Sgr object". SIMBAD. Retrieved 2010-18-04. {{cite web}}: Check date values in: |accessdate= (help)
  14. ^ Montes, D. (2001). "Late-type members of young stellar kinematic groups - I. Single stars". Monthly Notices of the Royal Astronomical Society. 328 (1): 45–63. doi:10.1046/j.1365-8711.2001.04781.x. Retrieved 2008-06-13. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: unflagged free DOI (link)
  15. ^ Allen, C. (1998). "The galactic orbits of nearby UV Ceti stars". Revista Mexicana de Astronomia y Astrofisica. 34: 37–46. Retrieved 2008-06-13. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  16. ^ Veeder, G. J. (1974). "Old disk flare stars". Astronomical Journal. 79: 702–704. doi:10.1086/111600. Retrieved 2008-06-13.
  17. ^ García-Sánchez, J. (2001). "Stellar encounters with the solar system". Astronomy and Astrophysics. 379: 634–659. doi:10.1051/0004-6361:20011330. Retrieved 2008-06-12. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  18. ^ Hinz, Joannah L. (2002). "A Near-Infrared Wide-Field Proper Motion Search for Brown Dwarfs". The Astronomical Journal. 123 (4): 2027–2032. doi:10.1086/339555. Retrieved 2008-06-12. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)


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