Astronomy:Rho2 Arietis

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Short description: Star in the constellation Aries


For other stars with this Bayer designation, see ρ Arietis.
ρ2 Arietis
Location of ρ2 Arietis (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Aries[1]
Right ascension  02h 55m 48.49800s[2]
Declination +18° 19′ 53.9029″[2]
Apparent magnitude (V) 5.93[3] (5.45–6.01)[4]
Characteristics
Evolutionary stage AGB[5][6]
Spectral type M6 III[7]
U−B color index +1.12[3]
B−V color index +1.51[3]
R−I color index +2.17[8]
Variable type SRb[4]
Astrometry
Radial velocity (Rv)+46.0[9] km/s
Proper motion (μ) RA: −7.78[2] mas/yr
Dec.: −14.98[2] mas/yr
Parallax (π)9.28 ± 0.30[2] mas
Distance350 ± 10 ly
(108 ± 3 pc)
Absolute magnitude (MV)+0.60[1]
Details
Mass1.21[6] M☉
Radius107.9±6.2[6] R☉
Luminosity1,390[6] L☉
Surface gravity (log g)0.5[10] cgs
Temperature3,400[10] K
Metallicity [Fe/H]–0.25[6] dex
Rotation<909[6] days
Rotational velocity (v sin i)6.0±0.5[10] km/s
Other designations
ρ2 Ari, 45 Arietis, RZ Arietis, BD+17 457, GC 3517, HD 18191, HIP 13654, HR 867, SAO 93189, PPM 118672[11]
Database references
SIMBADdata

Rho2 Arietis is an M-type red giant star in the northern constellation of Aries. Its name is a Bayer designation that is Latinized from ρ2 Arietis, and abbreviated Rho2 Ari or ρ2 Ari. The brightness of this star varies from magnitude 5.45 to 6.01,[12] making it faintly visible to the naked eye under good observing conditions. With an annual parallax shift of 9.28 mas,[2] it is approximately 350 light-years (110 parsecs) distant from the Earth. It is drifting further away from the Sun with a radial velocity of +46 km/s.[9]

A visual band light curve for Rho2 Arietis, plotted from data presented in Tabur et al. (2009)[13]

Rho2 Arietis is classified as a semiregular variable star with periods of 49.9 and 54.8 days.[13] It has the variable star designation, RZ Arietis.[4]

This is a red giant star with a stellar classification of M6 III;[7] it is probably on the asymptotic giant branch, having exhausted its core helium.[5][6] It is predicted to have started its life with 1.5 times the mass of the Sun, and is now down to 1.2 times the Sun's mass. At its current evolutionary stage Rho2 Arietis has expanded to 108 times the Sun's radius. It is radiating 1,390 times the Sun's luminosity from its photosphere at an effective temperature of 3,400 K.[6]

This star possesses a strong magnetic field, one of the strongest for M-type giants. It also possesses a high lithium abundance, higher than expected from evolutionary models. The strong magnetic field, rapid rotation and unusual lithium abundance suggest this star may have engulfed a planet when it was on the red-giant branch.[6]

References

  1. ↑ 1.0 1.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A.  XHIP record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  3. ↑ 3.0 3.1 3.2 Lee, T. A. (October 1970), "Photometry of high-luminosity M-type stars", Astrophysical Journal 162: 217, doi:10.1086/150648, Bibcode: 1970ApJ...162..217L. 
  4. ↑ 4.0 4.1 4.2 Samus, N. N. et al., "RZ Ari entry", Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.) (CDS), http://webviz.u-strasbg.fr/viz-bin/VizieR-S?V*%20RZ%20Ari%20V*, retrieved 2025-05-08.  ID II/250.
  5. ↑ 5.0 5.1 Eggen, Olin J. (1992), "Asymptotic Giant Branch Stars Near the Sun", The Astronomical Journal 104: 275, doi:10.1086/116239, Bibcode: 1992AJ....104..275E. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Konstantinova-Antova, R. et al. (January 2024), "A long-term study of the magnetic field and activity in the M giant RZ Ari - Magnetism and planet engulfment in a fairly evolved star?" (in en), Astronomy & Astrophysics 681: A36, doi:10.1051/0004-6361/202346949, ISSN 0004-6361, Bibcode: 2024A&A...681A..36K, https://www.aanda.org/articles/aa/full_html/2024/01/aa46949-23/aa46949-23.html, retrieved 2025-05-08. 
  7. ↑ 7.0 7.1 Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics 11: 29, doi:10.1146/annurev.aa.11.090173.000333, Bibcode: 1973ARA&A..11...29M. 
  8. ↑ Hoffleit, D.; Warren, Jr., W. H. (1991), "HR 867 entry", Bright Star Catalogue (CDS), http://webviz.u-strasbg.fr/viz-bin/VizieR-S?HR%20867, retrieved 2025-05-08.  ID V/50.
  9. ↑ 9.0 9.1 Famaey, B. et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics 430 (1): 165–186, doi:10.1051/0004-6361:20041272, Bibcode: 2005A&A...430..165F. 
  10. ↑ 10.0 10.1 10.2 Georgiev, Stefan et al. (June 2020), "Determining rotational and macroturbulent velocities of cool magnetic giant stars", Astronomische Nachrichten 341 (5): 486–492, doi:10.1002/asna.202013725, ISSN 0004-6337, Bibcode: 2020AN....341..486G. 
  11. ↑ "RZ Ari -- Semi-regular pulsating Star", SIMBAD Astronomical Database (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+18191, retrieved 2012-08-08. 
  12. ↑ RZ Ari, AAVSO, https://www.aavso.org/vsx/index.php?view=detail.top&oid=3700, retrieved 2024-11-27. 
  13. ↑ 13.0 13.1 Tabur, V. et al. (December 2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society 400 (4): 1945–1961, doi:10.1111/j.1365-2966.2009.15588.x, Bibcode: 2009MNRAS.400.1945T. 

Coordinates: Sky map 02h 55m 48.4978s, +18° 19′ 53.903″



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