YY Mensae

YY Mensae, also known as HD 32918, is a variable star located in the southern circumpolar constellation Mensa. It has an apparent magnitude that fluctuates between 8.6 and 8.9,^[3] which is within the visibility of binoculars. Based on parallax measurements from Gaia DR3, it is estimated to be 715 light years distant.^[2] It appears to be approaching the Solar System with a heliocentric radial velocity of −8.5 km/s.^[6]

YY Mensae

A light curve for YY Mensae, plotted from Hipparcos data[1]
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Mensa
Right ascension	04h 58m 17.93697s[2]
Declination	−75° 16′ 37.9879″[2]
Apparent magnitude (V)	8.60 - 8.89[3]
Characteristics
Spectral type	K1 III/IVe[4]
U−B color index	+0.70[5]
B−V color index	+1.04[5]
Variable type	FK Com[3]
Astrometry
Radial velocity (Rv)	−8.5±2.5[6] km/s
Proper motion (μ)	RA: −4.149 mas/yr[2] Dec.: −3.077 mas/yr[2]
Parallax (π)	4.5587 ± 0.0161 mas[2]
Distance	715 ± 3 ly (219.4 ± 0.8 pc)
Absolute magnitude (MV)	+0.81[7]
Details
Mass	0.983[8] M☉
Radius	12.3[9] R☉
Luminosity	68.5[10] L☉
Surface gravity (log g)	1.63[11] cgs
Temperature	4,691±128[12] K
Metallicity [Fe/H]	−0.59[11] dex
Rotational velocity (v sin i)	45±2[13] km/s
Other designations
YY Men, CD−75°189, CPD−75°292, HD 32918, HIP 23106[14]
Database references
SIMBAD	data

This star was known to have an unusual spectrum since the 1970's, but its variability wasn't observed until the 1980's. Collier (1982) found it to be a FK Comae Berenices variable, a class of rapidly rotating giant stars.^[15] After a few additional years of observations, HD 32918 was given the variable star designation YY Mensae.^[16] A paper in 1987 observed a long and powerful flare coming from the star.^[17] X-ray emissions from YY Mensa have been detected in its corona, which may be a result of its fast rotation.^[18]

YY Mensae has a stellar classification of K1 III/IVe,^[4] indicating an evolved red giant with the blended luminosity class of a giant star and a subgiant. It is chromospherically active and emission lines are also present in its spectra. It has 98% the mass of the Sun^[8] but has expanded to 12.3 times its girth.^[9] It radiates 68.5 times the luminosity of the Sun^[10] from its photosphere at an effective temperature of 4,691 K,^[12] giving it an orange hue. Typical for stars its type, YY Mensae spins rapidly, having a projected rotational velocity of 45 km/s.^[13] The star is metal deficient, having an iron abundance only 26% that of the Sun.^[11]

References

1. "Light Curve". Hipparcos ESA. ESA. Retrieved 17 February 2022.
2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
3. Samus’, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (January 2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. eISSN 1562-6881. ISSN 1063-7729. S2CID 125853869.
4. Bidelman, W. P.; MacConnel, D. J. (October 1973). "The brighter stars of astrophysical interest in the southern sky". The Astronomical Journal. 78: 687. Bibcode:1973AJ.....78..687B. doi:10.1086/111475. ISSN 0004-6256.
5. Cutispoto, G.; Messina, S.; Rodonò, M. (March 2001). "Long-term monitoring of active stars". Astronomy & Astrophysics. 367 (3): 910–930. Bibcode:2001A&A...367..910C. doi:10.1051/0004-6361:20000549. eISSN 1432-0746. ISSN 0004-6361.
6. Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
7. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
8. Anders, F.; et al. (February 2022). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G = 18.5". Astronomy & Astrophysics. 658: A91. arXiv:2111.01860. Bibcode:2022A&A...658A..91A. doi:10.1051/0004-6361/202142369. eISSN 1432-0746. ISSN 0004-6361.
9. Strassmeier, Klaus G. (2 May 2009). "Starspots". The Astronomy and Astrophysics Review. 17 (3): 251–308. Bibcode:2009A&ARv..17..251S. doi:10.1007/s00159-009-0020-6. eISSN 1432-0754. ISSN 0935-4956.
10. McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (21 November 2012). "Fundamental parameters and infrared excesses of Hipparcos stars: Parameters and IR excesses from Hipparcos". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711.
11. Sprague, Dani; et al. (8 March 2022). "APOGEE Net: An Expanded Spectral Model of Both Low-mass and High-mass Stars". The Astronomical Journal. 163 (4): 152. arXiv:2201.03661. Bibcode:2022AJ....163..152S. doi:10.3847/1538-3881/ac4de7. eISSN 1538-3881. ISSN 0004-6256.
12. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881.
13. Fekel, Francis C.; Balachandran, Suchitra (February 1993). "Lithium and rapid rotation in chromospherically active single giants". The Astrophysical Journal. 403: 708. Bibcode:1993ApJ...403..708F. doi:10.1086/172242. eISSN 1538-4357. ISSN 0004-637X.
14. "YY Mensae". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 28, 2022.
15. Collier, A. C. (August 1982). "Discovery of two FK Comae stars in the southern hemisphere". Monthly Notices of the Royal Astronomical Society. 200: 489–496. Bibcode:1982MNRAS.200..589C. doi:10.1093/mnras/200.3.589 (inactive 1 November 2024). ISSN 0035-8711.{{cite journal}}: CS1 maint: DOI inactive as of November 2024 (link)
16. Kholopov, P. N.; Samus, N. N.; Kazarovets, E. V.; Perova, N. B. (March 1985). "The 67th Name-List of Variable Stars". Information Bulletin on Variable Stars. 2681: 1. Bibcode:1985IBVS.2681....1K. ISSN 0374-0676.
17. Slee, O. B.; Nelson, G. J.; Stewart, R. T.; Wright, A. E.; Jauncey, D. L.; Heisler, L. H.; Bunton, J. D.; Vaughan, A. E.; Large, M. I.; Peters, W. L.; Ryan, S. G. (1 July 1987). "A very intense, long-lasting radio flare on HD 32918". Monthly Notices of the Royal Astronomical Society. 227 (2): 467–479. Bibcode:1987MNRAS.227..467S. doi:10.1093/mnras/227.2.467. eISSN 1365-2966. ISSN 0035-8711.
18. Audard, Marc; Telleschi, Alessandra; Gudel, Manuel; Skinner, Stephen L.; Pallavicini, Roberto; Mitra-Kraev, Urmila (10 December 2004). "Some Like It Hot: The X-Ray Emission of the Giant Star YY Mensae". The Astrophysical Journal. 617 (1): 531–550. arXiv:astro-ph/0408345. Bibcode:2004ApJ...617..531A. doi:10.1086/424590. eISSN 1538-4357. ISSN 0004-637X.

Further reading

Audard, M.; Güdel, M.; Skinner, S. L.; Pallavicini, R.; Drake, S. A.; Mewe, R. (December 2002). "Chandra and XMM-Newton X-Ray Spectroscopy of the Hot Corona of YY Mensae". American Astronomical Society Meeting Abstracts. 201: 33.07. Bibcode:2002AAS...201.3307A.

Strassmeier, K.G. (August 2002). "Doppler images of starspots". Astronomische Nachrichten. 323 (3–4): 309–316. Bibcode:2002AN....323..309S. doi:10.1002/1521-3994(200208)323:3/4<309::AID-ASNA309>3.0.CO;2-U. eISSN 1521-3994. ISSN 0004-6337.

Gondoin, P. (December 1999). "Evolution of X-ray activity and rotation on G-K giants". Astronomy and Astrophysics. 352: 217–227. Bibcode:1999A&A...352..217G. ISSN 0004-6361.

Grewing, M.; Bianchi, L.; Cassatella, A. (August 1986). "HD 32918 : Ultraviolet spectrum and optical behaviour". Astronomy and Astrophysics. 164: 31–39. Bibcode:1986A&A...164...31G. ISSN 0004-6361.