YY Mensae Last updated July 13, 2025 Star in the constellation of Mensa
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]
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 ↑ "Light Curve" . Hipparcos ESA . ESA. Retrieved 17 February 2022 . 1 2 3 4 5 6 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 . 1 2 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 . 1 2 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 . 1 2 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 . 1 2 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 . ↑ 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 . 1 2 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 . 1 2 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 . 1 2 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 . 1 2 3 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 . 1 2 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 . 1 2 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 . ↑ "YY Mensae" . SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved September 28, 2022 . ↑ 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 12 July 2025). ISSN 0035-8711 . {{cite journal }}
: CS1 maint: DOI inactive as of July 2025 (link ) ↑ 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 . ↑ 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 . ↑ 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 .
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