HK Aquarii
Appearance
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aquarius |
Right ascension | 23h 08m 19.551s [1] |
Declination | 15° 24′ 35.77″[1] |
Apparent magnitude (V) | 10.72 - 10.94[2] |
Characteristics | |
Evolutionary stage | Red dwarf |
Spectral type | M0Ve[3] |
U−B color index | +1.118[4] |
B−V color index | +1.41[4] |
Variable type | BY Dra[5] |
Astrometry | |
Proper motion (μ) | RA: 106.955[1] mas/yr Dec.: -18.738[1] mas/yr |
Parallax (π) | 40.1410 ± 0.0436 mas[1] |
Distance | 81.25 ± 0.09 ly (24.91 ± 0.03 pc) |
Absolute magnitude (MV) | +9.13[4] |
Details | |
Mass | 0.5[5] M☉ |
Radius | 0.6[5] R☉ |
Other designations | |
Database references | |
SIMBAD | data |
HK Aquarii (Gliese 890) is a variable star—technically a BY Draconis variable—noteworthy for being unusually active for an isolated red dwarf; it rotates rapidly, generating a strong magnetic field that creates large starspots and powerful flares. These are characteristic of very young stars; although it is not close to any youthful open cluster, it is a possible ejected member of the Pleiades.[5]
References
- ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
- ^ Torres, C. A. O.; Quast, G. R.; Da Silva, L.; de la Reza, R.; Melo, C. H. F.; Sterzik, M. (2006). "Search for associations containing young stars (SACY). I. Sample and searching method". Astronomy and Astrophysics. 460 (3): 695. arXiv:1505.07837. Bibcode:2006A&A...460..695T. doi:10.1051/0004-6361:20065602.
- ^ a b c Koen, C.; Kilkenny, D.; Van Wyk, F.; Marang, F. (2010). "UBV(RI)C JHK observations of Hipparcos-selected nearby stars". Monthly Notices of the Royal Astronomical Society. 403 (4): 1949. Bibcode:2010MNRAS.403.1949K. doi:10.1111/j.1365-2966.2009.16182.x.
- ^ a b c d Crosswell, Ken. "A Star that Breaks all the Rules." The New Cosmos. Astronomy Magazine, Kalmbach Books, 1992, pp. 54-59.