BO Microscopii

BO Microscopii (BO Mic) is a star in the constellation Microscopium located about 170 light-years (52 parsecs; 11 million astronomical units) from the Sun. It has been dubbed "Speedy Mic" because of its very rapid rotation. The projected rotational velocity at the equator of this star is about 135 km/s (84 mi/s), which, with an estimated inclination of 70° to the line of sight from the Earth, means it completes a rotation every 0.380 ± 0.004 days (9.120 ± 0.096 hours). The photosphere of this star shows a high level of magnetic activity, with multiple star spots and prominences observed at the same time. As many as 25 prominences have been observed simultaneously, extending outward as far as 3.6 times the radius of the star. BO Mic is a flare star that undergoes sudden increases in X-ray and ultraviolet emissions. These events can emit a hundred times more energy than large solar flares.[7] Speedy Mic is one of the most active stars in the vicinity of the Sun.[5]

BO Microscopii

A visual band light curve for BO Microscopii, adapted from Cutispoto et al. (1997)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Microscopium
Right ascension 20h 47m 45.00562s[2]
Declination −36° 35′ 40.7698″[2]
Apparent magnitude (V) 9.39[3]
Characteristics
Spectral type K3Ve[3]
Variable type Flare star
Astrometry
Radial velocity (Rv)−5.64±2.03[2] km/s
Proper motion (μ) RA: 18.735 mas/yr[2]
Dec.: −81.712 mas/yr[2]
Parallax (π)19.5983 ± 0.5745 mas[2]
Distance166 ± 5 ly
(51 ± 1 pc)
Absolute magnitude (MV)5.92[4]
Details
Mass0.82±0.08[5] M☉
Radius1.06±0.04[5] R☉
Temperature4750±50[6] K
Metallicity [Fe/H]−1.49[4] dex
Rotation0.380±0.004 days[1]
Rotational velocity (v sin i)135[7] km/s
Age33±5[6] Myr
Other designations
Speedy Mic, BO Mic, CD−37 13926, CPD−37 8883, HD 197890, HIP 102626, SAO 212437, PPM 300614, TIC 389423271, TYC 7469-997-1, GSC 07469-00997
Database references
SIMBADdata

References
  1. Cutispoto, G.; Kurster, M.; Pagano, I.; Rodono, M. (January 1997). "UBV(RI)c Photometry of the Rapidly Rotating K-Type Star HD197890 = "Speedy Mic"". Information Bulletin on Variable Stars. 4419: 1. Bibcode:1997IBVS.4419....1C. Retrieved 28 January 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. Torres, C. A. O.; et al. (December 2006), "Search for associations containing young stars (SACY). I. Sample and searching method", Astronomy and Astrophysics, 460 (3): 695–708, arXiv:astro-ph/0609258, Bibcode:2006A&A...460..695T, doi:10.1051/0004-6361:20065602, S2CID 16080025
  4. Holmberg, J.; Nordström, B.; Andersen, J. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511
  5. Dunstone, N. J.; et al. (January 2006), "The coronal structure of Speedy Mic - I. A densely packed prominence system beyond corotation", Monthly Notices of the Royal Astronomical Society, 365 (2): 530–538, arXiv:astro-ph/0510739, Bibcode:2006MNRAS.365..530D, doi:10.1111/j.1365-2966.2005.09729.x, S2CID 11048210
  6. Wolter, U.; et al. (May 2005), "Doppler imaging of Speedy Mic using the VLT. Fast spot evolution on a young K-dwarf star", Astronomy and Astrophysics, 435 (1): 261–273, arXiv:astro-ph/0504104, Bibcode:2005A&A...435..261W, doi:10.1051/0004-6361:20042239
  7. Wolter, U.; et al. (January 2008), "Doppler imaging an X-ray flare on the ultrafast rotator BO Mic. A contemporaneous multiwavelength study using XMM-Newton and VLT", Astronomy and Astrophysics, 478 (1): L11–L14, arXiv:0712.0899, Bibcode:2008A&A...478L..11W, doi:10.1051/0004-6361:20078838, S2CID 62827486
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