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ρ Arietis

Location of ρ Arietis (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Aries
Right ascension	02 55 48.49800
Declination	+18° 19′ 53.9029″
Apparent magnitude (V)	5.93 (5.45–6.01)
Characteristics
Spectral type	M6 III
U−B color index	+1.12
B−V color index	+1.51
R−I color index	2.17
Variable type	SRb
Astrometry
Radial velocity (Rv)	+46.0 km/s
Proper motion (μ)	RA: −7.78 mas/yr Dec.: −14.98 mas/yr
Parallax (π)	9.28 ± 0.30 mas
Distance	350 ± 10 ly (108 ± 3 pc)
Absolute magnitude (MV)	+0.60
Details
Mass	1.21 M☉
Radius	107.9±6.2 R☉
Luminosity	1,390 L☉
Surface gravity (log g)	0.5 cgs
Temperature	3,400 K
Metallicity	–0.25 dex
Rotation	<909 days
Rotational velocity (v sin i)	6.0±0.5 km/s
Other designations
ρ Ari, 45 Arietis, RZ Arietis, BD+17 457, HD 18191, HIP 13654, HR 867, SAO 93189.
Database references
SIMBAD	data

Rho Arietis is an M-type red giant star in the northern constellation of Aries. Its brightness varies from magnitude 5.45 to 6.01, making it faintly visible to the naked eye under good observing conditions. With an annual parallax shift of 9.28 mas, it is approximately 350 light-years (110 parsecs) distant from the Earth.

Rho Arietis is classified as a semiregular variable star with periods of 49.9 and 54.8 days. It has the variable star designation, RZ Arietis. It is probably an asymptotic giant branch star, having exhausted its core helium. It is predicted to have started its life with 1.5 solar masses. At its current evolutionary stage, Rho Arietis has expanded to 108 times the Sun's radius and is radiating 1,400 times the Sun's luminosity.

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 might be explained by a planet engulfment, when the star was on the red-giant branch.

References

1. ^ van Leeuwen, F. (November 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, S2CID 18759600.
2. ^ Lee, T. A. (October 1970), "Photometry of high-luminosity M-type stars", Astrophysical Journal, 162: 217, Bibcode:1970ApJ...162..217L, doi:10.1086/150648.
3. ^ V* RZ Ari, entry, Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.), N. N. Samus, O. V. Durlevich, et al., CDS ID II/250.
4. Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics, 11: 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333.
5. HR 867, entry, Bright Star Catalogue, 5th Revised Ed., D. Hoffleit and W. H. Warren, Jr., 1991, CDS ID V/50.
6. 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, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304.
7. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
8. ^ Konstantinova-Antova, R.; Georgiev, S.; Lèbre, A.; Palacios, A.; Morin, J.; Bogdanovski, R.; Abbott, C.; Baron, F.; Aurière, M.; Drake, N. A.; Tsvetkova, S.; Josselin, E.; Paladini, C.; Mathias, P.; Zamanov, R. (2024-01-01). "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?". Astronomy & Astrophysics. 681: A36. arXiv:2312.12549. doi:10.1051/0004-6361/202346949. ISSN 0004-6361.
9. ^ Georgiev, Stefan; Lèbre, Agnès; Josselin, Eric; Konstantinova-Antova, Renada; Morin, Julien (June 2020). "Determining rotational and macroturbulent velocities of cool magnetic giant stars". Astronomische Nachrichten. 341 (5): 486–492. arXiv:2202.00971. doi:10.1002/asna.202013725. ISSN 0004-6337.
10. "RZ Ari -- Semi-regular pulsating Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-08-08.
11. "RZ Ari". The International Variable Star Index. AAVSO. Retrieved 27 November 2024.
12. ^ 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, arXiv:0908.3228, Bibcode:2009MNRAS.400.1945T, doi:10.1111/j.1365-2966.2009.15588.x, S2CID 15358380.
13. Eggen, Olin J. (1992). "Asymptotic Giant Branch Stars Near the Sun". The Astronomical Journal. 104: 275. Bibcode:1992AJ....104..275E. doi:10.1086/116239.

v t e Constellation of Aries
Aries in Chinese astronomy List of stars in Aries
Stars	Bayer α (Hamal) β (Sheratan) γ (Mesarthim) δ (Botein) ε ζ η θ ι κ λ μ ν ξ ο π ρ ρ ρ σ τ τ Flamsteed 1 4 7 10 11 14 15 16 19 20 21 23 26 27 29 30 31 33 35 36 38 39 (Lilii Borea) 40 41 (Bharani) 47 49 50 51 52 53 54 55 56 59 60 62 64 65 66 54 Cet 85 Cet Variable TZ UX VZ (16 Tri) HR 577 728 803 952 999 HD 12661 20367 Other BD+20°307 HIP 14810 HAT-P-25 Teegarden's Star WASP-11/HAT-P-10 WD 0145+234
Exoplanets α Arietis b HD 12661 b c HIP 14810 b c d Teegarden's Star b c WASP-11b/HAT-P-10b
Galaxies	NGC 677 680 691 694 695 716 765 770 772 781 803 817 820 821 871 877 900 901 903 904 918 935 938 972 990 992 1024 1134 1156 Other 1ES 0229+200 3C 79 4C +28.07 AO 0235+164 IC 167 IC 1801 PSO J0309+27 Segue 2 UGC 2140
Galaxy clusters MS 0302+17
Astronomical events GRB 060218
Category

• Flamsteed objects
• Bayer objects
• Hipparcos objects
• Henry Draper Catalogue objects
• M-type giants
• Aries (constellation)
• Semiregular variable stars
• Bright Star Catalogue objects
• Durchmusterung objects
• Objects with variable star designations