HR 1099

HR 1099 is a triple star system in the equatorial constellation of Taurus, positioned 11′ to the north of the star 10 Tauri.[15] This system has the variable star designation V711 Tauri, while HR 1099 is the star's identifier from the Bright Star Catalogue. It ranges in brightness from a combined apparent visual magnitude of 5.71 down to 5.94,[6] which is bright enough to be dimly visible to the naked eye. The distance to this system is 96.6 light years based on parallax measurements,[1] but it is drifting closer with a radial velocity of about −15 km/s.

HR 1099
Chart showing the position of the stars in the constellation Taurus
Location of HR 1099 (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Taurus
A
Right ascension 03h 36m 47.291s[1]
Declination 00° 35′ 15.94″[1]
Apparent magnitude (V) 5.91[2]
B
Right ascension 03h 36m 46.844s[3]
Declination 00° 35′ 15.93″[3]
Apparent magnitude (V) 8.79[2]
Characteristics
Spectral type K2:Vnk[4] (K1 IV + G5 V + K3 V)[5]
Variable type RS CVn[6]
Astrometry
A
Radial velocity (Rv)−21.24±6.62[1] km/s
Proper motion (μ) RA: −32.894 mas/yr[1]
Dec.: −161.772 mas/yr[1]
Parallax (π)33.7528 ± 0.0866 mas[1]
Distance96.6 ± 0.2 ly
(29.63 ± 0.08 pc)
Absolute magnitude (MV)3.6[2]
B
Radial velocity (Rv)−15.34±0.18[3] km/s
Proper motion (μ) RA: −34.359 mas/yr[3]
Dec.: −138.137 mas/yr[3]
Parallax (π)33.8664 ± 0.0226 mas[3]
Distance96.31 ± 0.06 ly
(29.53 ± 0.02 pc)
Absolute magnitude (MV)6.5[2]
Orbit[7]
Period (P)2.83774 d
Semi-major axis (a)10.3 R☉[8]
Eccentricity (e)0.00 (assumed)
Inclination (i)38[9]°
Periastron epoch (T)2,442,767.4 HJD
Argument of periastron (ω)
(secondary)		0.00 (assumed)°
Semi-amplitude (K1)
(primary)		52.6 km/s
Semi-amplitude (K2)
(secondary)		64.1 km/s
Details
Component Aa
Mass1.0[8] M☉
Radius3.7[8] R☉
Surface gravity (log g)3.30[5] cgs
Temperature4,750[5] K
Metallicity [Fe/H]−0.16[10] dex
Rotational velocity (v sin i)39[9] km/s
Component Ab
Mass0.8[8] M☉
Radius1.1[8] R☉
Surface gravity (log g)4.26[5] cgs
Temperature5,500[5] K
Component B
Mass0.78[11] M☉
Radius0.78[11] R☉
Luminosity0.30[11] L☉
Surface gravity (log g)4.55[11] cgs
Temperature4,829[11] K
Metallicity [Fe/H]+0.10[10] dex
Rotational velocity (v sin i)4.1[12] km/s
Age2.2[3] Gyr
Other designations
STF 422, V711 Tau, BD+00°616, GC 4311, HD 22468, HIP 16846, HR 1099, SAO 111291, PPM 146726, ADS 2644, WDS J03368+0035[13][14]
Database references
SIMBADdata

This system was discovered to be a double star by F. G. W. Struve in 1822, with the components A and B having an angular separation of 5.4″. (The separation was measured at 6.7″ in 2016.)[16] R. E. Wilson in 1953 determined that the brighter member of this pair, component A, has a variable radial velocity. In 1963, O. C. Wilson noted that the same component shows very high emission cores in the calcium H and K absorption lines.[17] Follow-up observations by O. C. Wilson in 1964 showed that the hydrogen–α line of component A is fully in emission and it displays moderate broadening due to rotation. He found a stellar classification of K3 V for component B, matching an ordinary K-type main-sequence star.[18]

A light curve for V711 Tauri, plotted from TESS data[19]

Observations during 1974–1975 demonstrated that component A is a spectroscopic binary star system of the RS Canum Venaticorum variable class. Given its average magnitude of around 5.9, it is one of the brighter known variables of this type.[20] No eclipses were observed, but an orbital period of 2.838 days was determined. Most of the emission was found to be coming from the more massive member of this pair.[21] Radio emission from the binary was detected by F. N. Owen in 1976.[22] It was shown to be a soft X-ray source in 1978 using the HEAO 1 satellite.[23]

This double-lined spectroscopic binary system consists of an evolving K-type subgiant and an ordinary G-type main sequence star. The two stars are orbiting so close to each other that their tidal effects are giving them an elliptical shape. The subgiant is filling about 80% of its Roche lobe.[5] The chromosphere of the subgiant is one of the most active known, with a deep convective zone powering the magnetic dynamo.[24][4] The G-type companion has a shallow convection zone and is less active.[5]

In 1980, significant variations were found in some spectral features related to surface temperature, suggesting the presence of starspots.[25] Doppler imaging confirmed these starspots are associated with the K subgiant. (It was the first cool star to have its surface Doppler imaged.[26]) The evidence suggests that the spots first appear at low latitude then migrated toward the poles.[20] These spots are much larger than they are on the Sun.[5] About 70% of all spots have been observed at latitudes higher than 50°, particularly around the polar region.[9][24] A polar spot has persisted for at least twenty years.[5]

The baseline apparent magnitudes of the two stars, after subtracting the effects of starspots, is 5.80 and 7.20.[5] Long term monitoring indicates the subgiant has two activity cycles, similar to the 11-year solar cycle. A 5.3±0.1 year cycle is associated with symmetrical flip-flopping of the spotted area between hemispheres. The longer 15–16 year cycle is a periodic variation in the total spot area. The global magnetic field of the star may be precessing with respect to the axis of rotation.[26]

See also

References
  1. 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.
  2. Freund, S.; Robrade, J.; Schneider, P. C.; Schmitt, J. H. M. M. (2018), "The stellar content of the XMM-Newton slew survey", Astronomy and Astrophysics, 614: A125, arXiv:1712.07410, Bibcode:2018A&A...614A.125F, doi:10.1051/0004-6361/201732009, S2CID 59396964.
  3. 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.
  4. Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc—The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
  5. Lanza, A. F.; et al. (August 2006), "Long-term starspot evolution, activity cycle, and orbital period variation of V711 Tauri (HR 1099)", Astronomy and Astrophysics, 455 (2): 595–606, Bibcode:2006A&A...455..595L, doi:10.1051/0004-6361:20064847.
  6. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  7. Strassmeier, K. G.; Bartus, J. (February 2000), "Doppler imaging of stellar surface structure. XII. Rapid spot changes on the RS CVn binary V711 Tauri = HR 1099", Astronomy and Astrophysics, 354: 537–550, Bibcode:2000A&A...354..537S.
  8. Donati, J. -F. (January 1999), "Magnetic cycles of HR 1099 and LQ Hydrae", Monthly Notices of the Royal Astronomical Society, 302 (3): 457–481, Bibcode:1999MNRAS.302..457D, doi:10.1046/j.1365-8711.1999.02096.x.
  9. Donati, J. -F.; et al. (November 2003), "Dynamo processes and activity cycles of the active stars AB Doradus, LQ Hydrae and HR 1099", Monthly Notices of the Royal Astronomical Society, 345 (4): 1145–1186, Bibcode:2003MNRAS.345.1145D, doi:10.1046/j.1365-2966.2003.07031.x.
  10. Soubiran, Caroline; et al. (2016), "The PASTEL catalogue: 2016 version", Astronomy & Astrophysics, 591: A118, arXiv:1605.07384, Bibcode:2016A&A...591A.118S, doi:10.1051/0004-6361/201628497, S2CID 119258214.
  11. Stassun K.G.; et al. (October 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, S2CID 166227927.
  12. Luck, R. Earle (January 2017), "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants", The Astronomical Journal, 153 (1): 19, arXiv:1611.02897, Bibcode:2017AJ....153...21L, doi:10.3847/1538-3881/153/1/21, S2CID 119511744, 21.
  13. "HD 22468A". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2023-01-04.
  14. "HD 22468B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2023-01-04.
  15. Sinnott, Roger W.; Perryman, Michael A. C. (1997), Millennium Star Atlas, vol. 1, Sky Publishing Corporation and the European Space Agency, p. 260, ISBN 0-933346-84-0.
  16. Mason, Brian D.; et al. (2001), "The Washington Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  17. Wilson, O. C. (October 1963), "A Probable Correlation Between Chromospheric Activity and Age in Main-Sequence Stars", Astrophysical Journal, 138: 832, Bibcode:1963ApJ...138..832W, doi:10.1086/147689.
  18. Wilson, O. C. (August 1964), "Chromospheric Activity and Lithium", Publications of the Astronomical Society of the Pacific, 76 (451): 238, Bibcode:1964PASP...76..238W, doi:10.1086/128091, S2CID 111386087.
  19. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 22 January 2023.
  20. Vogt, S. S.; Penrod, G. D. (September 1983), "Doppler imaging of spotted stars : application to the RS Canum Venaticorum star HR 1099", Publications of the Astronomical Society of the Pacific, 95: 565–576, Bibcode:1983PASP...95..565V, doi:10.1086/131208, S2CID 123206530.
  21. Bopp, B. W.; Fekel, F., Jr. (September 1976), "HR 1099: a new bright RS CVn variable", Astronomical Journal, 81: 771–774, Bibcode:1976AJ.....81..771B, doi:10.1086/111951, hdl:2152/34302.{{citation}}: CS1 maint: multiple names: authors list (link)
  22. Owen, F. N. (March 1976), Marsden, B. G. (ed.), "HR 1099", IAU Circular, 2929: 2, Bibcode:1976IAUC.2929....2O.
  23. Walter, F.; Charles, P.; Bowyer, S. (August 1978), "Discovery of quiescent X-ray emission from HR 1099, RS CVn", Nature, 274 (5671): 569–570, Bibcode:1978Natur.274R.569W, doi:10.1038/274569b0, S2CID 4206226.
  24. Petit, P.; et al. (March 2004), "Magnetic topology and surface differential rotation on the K1 subgiant of the RS CVn system HR 1099", Monthly Notices of the Royal Astronomical Society, 348 (4): 1175–1190, arXiv:astro-ph/0312238, Bibcode:2004MNRAS.348.1175P, doi:10.1111/j.1365-2966.2004.07420.x, S2CID 119463091.
  25. Ramsey, L. W.; Nations, H. L. (August 1980), "HR 1099 and the starspot hypothesis for RS CVn binaries", Astrophysical Journal, 239: L121–L124, Bibcode:1980ApJ...239L.121R, doi:10.1086/183306.
  26. Berdyugina, Svetlana V.; Henry, Gregory W. (April 2007), "Butterfly Diagram and Activity Cycles in HR 1099", Astrophysical Journal, 659 (2): L157–L160, arXiv:astro-ph/0703530, Bibcode:2007ApJ...659L.157B, doi:10.1086/517881, S2CID 14242208.

Further reading
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