Rho2 Arietis

For other stars with this Bayer designation, see ρ Arietis.

ρ^2 Arietis

Location of ρ^2 Arietis (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Aries
Right ascension	02^h 55^m 48.49800^s[1]
Declination	+18° 19′ 53.9029″[1]
Apparent magnitude (V)	5.93[2] (5.45–6.01)[3]
Characteristics
Spectral type	M6 III[4]
U−B color index	+1.12[2]
B−V color index	+1.51[2]
R−I color index	2.17[5]
Variable type	SRb[3]
Astrometry
Radial velocity (Rv)	+46.0[6] km/s
Proper motion (μ)	RA: −7.78[1] mas/yr Dec.: −14.98[1] mas/yr
Parallax (π)	9.28 ± 0.30 mas[1]
Distance	350 ± 10 ly (108 ± 3 pc)
Absolute magnitude (MV)	+0.60[7]
Details
Mass	1.21[8] M☉
Radius	107.9±6.2[8] R☉
Luminosity	1,390[8] L☉
Surface gravity (log g)	0.5[9] cgs
Temperature	3,400[9] K
Metallicity [Fe/H]	–0.25[8] dex
Rotation	<909[8] days
Rotational velocity (v sin i)	6.0±0.5[9] km/s
Other designations
ρ^2 Ari, 45 Arietis, RZ Arietis, BD+17 457, HD 18191, HIP 13654, HR 867, SAO 93189.[10]
Database references
SIMBAD	data

Rho^2 Arietis is an M-type red giant star in the northern constellation of Aries. Its brightness varies from magnitude 5.45 to 6.01,[11] making it faintly visible to the naked eye under good observing conditions. With an annual parallax shift of 9.28 mas,[1] it is approximately 350 light-years (110 parsecs) distant from the Earth.

A visual band light curve for Rho^2 Arietis, plotted from data presented in Tabur et al. (2009)[12]

Rho^2 Arietis is classified as a semiregular variable star with periods of 49.9 and 54.8 days.[12] It has the variable star designation, RZ Arietis.[3] It is probably an asymptotic giant branch star, having exhausted its core helium.[13][8] It is predicted to have started its life with 1.5 solar masses. At its current evolutionary stage, Rho^2 Arietis has expanded to 108 times the Sun's radius and is radiating 1,400 times the Sun's luminosity.[8]

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.[8]

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. Bibcode:2024A&A...681A..36K. 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. Bibcode:2020AN....341..486G. 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.