YY Mensae

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YY Mensae
YYMenLightCurve.png
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

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]

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References

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  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 31 January 2024). ISSN   0035-8711.{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link)
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  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.