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 | |
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]
{{
cite journal}}
: CS1 maint: DOI inactive as of January 2024 (
link)
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.
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 | |
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]
{{
cite journal}}
: CS1 maint: DOI inactive as of January 2024 (
link)
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.