119 Tauri

119 Tauri (also known as CE Tauri) is a red supergiant star in the constellation Taurus. It is a semiregular variable and its angular diameter has been measured at about 10 mas.

119 Tauri

The sky position of 119 Tauri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Taurus
Right ascension  05h 32m 12.75251s[1]
Declination +18° 35′ 39.2436″[1]
Apparent magnitude (V) 4.23 - 4.54[2]
Characteristics
Evolutionary stage asymptotic giant branch[3]
Spectral type M2Iab-Ib[2]
U−B color index +2.23[4]
B−V color index +2.08[4]
Variable type SRc[2]
Astrometry
Radial velocity (Rv)+23.75[5] km/s
Proper motion (μ) RA: 1.86[1] mas/yr
Dec.: −4.48[1] mas/yr
Parallax (π)1.82 ± 0.26[1] mas
Distanceapprox. 1,800 ly
(approx. 550 pc)
Absolute magnitude (MV)−5.20[6]
Details
Mass14.37+2.00
−2.77[7] M☉
Radius587 - 593[7] R☉
Luminosity66,000[7] L☉
Surface gravity (log g)+0.05+0.11
−0.17[7] cgs
Temperature3,801 - 3,820[7] K
Metallicity0.0[3]
Age13.9+1.0
−2.5[7] Myr
Other designations
CE Tauri, HR 1845, HD 36389, BD+18°875, HIP 25945, SAO 94628, GC 6841, AAVSO 0526+18, Ruby Star[8]
Database references
SIMBADdata

Description

119 Tauri has a spectral class of M2 and a luminosity class of Iab-Ib, intermediate between an intermediate-luminosity supergiant and a less luminous supergiant. It is approximately 1,800 light years from Earth, and with a colour index of +2.07 it is one of the reddest naked eye stars in the night sky.[4] It is a similar star to Betelgeuse although redder and more distant.[6]

119 Tauri is classified as a semiregular variable star and has been given the variable star designation CE Tauri. The General Catalogue of Variable Stars gives a magnitude range from +4.23 to +4.54 with a period of 165 days.[2] Other published studies find poorly-defined periodicity, but with possible periods around 270 and 1,300 days.[9][10][11] Its infrared magnitude changes much less than the visual magnitude; the visual brightness changes are driven by changes in temperature which shift the proportion of electromagnetic radiation emitted in the visual range.[6]

Occultations

CE Tauri lies 4.6 degrees off the ecliptic.[12] This makes it a candidate for occultations by the Moon and (extremely rarely) by one of the bright planets. The star's angular diameter has been measured by lunar occultation, giving limb-darkened visible light angular diameters of 9.1±0.8 mas,[13] 10.9±1.0 mas,[14] and 9.0±0.2 mas.[15] An occultation has also been observed in H-alpha, giving a diameter of 17±1 mas, which indicates that there is circumstellar hydrogen producing emission across at least that size, nearly twice the visible diameter.[15]

Angular diameter

The angular diameter of 119 Tauri has also been measured directly by VLBI, leading to limb-darkened diameters of 10.68±0.21 mas,[16] 9.83±0.07 mas,[17] 9.3±0.5 mas,[18] 9.97±0.08 mas,[3] 10.24±0.05 mas,[7] 9.68±0.05 mas.[7] Although CE Tauri is classified as a pulsating variable, observations using the same equipment and wavelengths have not detected significant changes in the angular diameter over time.[3] Reconstructed images of the surface show bright spots that are attributed to giant convection cells.[7]

Properties

Angular diameter measurements can be combined with absolute observed fluxes to derive an accurate effective temperature, about 3,800 K for 119 Tauri. Combined with a distance, the linear size of the star can be calculated. CE Tauri is found to have a radius between 587 to 593 R☉. Then the bolometric luminosity is the star is found to be about 66,000 L☉. However, the distance to 119 Tauri is still only known approximately from its Hipparcos parallax. Gaia Data Release 2 gives a distinctly larger parallax, but with even greater uncertainty and flagged as unreliable.[19]

119 Tauri is a pulsating star although the pulsation has not been clearly detected in direct angular measurements. Observations of TiO lines in its spectrum as its brightness changes show effective temperature changes up to 100 K. Calculating its physical properties shows that the bolometric luminosity and radius both change by about 10%, with the radius typically being larger at cooler temperatures.[6]

Comparison of its properties with stellar evolutionary tracks shows CE Tauri to have evolved from an initial mass of 15 M☉ and to have a current mass of 14.37 M☉.[7] An alternative interpretation of observations, under the assumption that CE Tauri is an asymptotic giant branch (AGB) star, give it a current mass of 8 M☉ and a luminosity of 44,000 L☉.[3]

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References
  1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. 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: 02025. Bibcode:2009yCat....102025S.
  3. Cruzalebes, P.; Jorissen, A.; Rabbia, Y.; Sacuto, S.; Chiavassa, A.; Pasquato, E.; Plez, B.; Eriksson, K.; Spang, A.; Chesneau, O. (2013). "Fundamental parameters of 16 late-type stars derived from their angular diameter measured with VLTI/AMBER". Monthly Notices of the Royal Astronomical Society. 434 (1): 437–450. arXiv:1306.3288. Bibcode:2013MNRAS.434..437C. doi:10.1093/mnras/stt1037.
  4. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  5. Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data". Astronomy and Astrophysics. 430 (1): 165–186. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272.
  6. Wasatonic, R. & Guinan, E. F. (1998). "Variations of Luminosity, Radius, and Temperature of the Pulsating Red Supergiant CE Tauri". Information Bulletin on Variable Stars. 4629: 1. Bibcode:1998IBVS.4629....1W.
  7. Montargès, M; Norris, R; Chiavassa, A; Tessore, B; Lèbre, A; Baron, F (2018). "The convective photosphere of the red supergiant CE Tau. I. VLTI/PIONIER H-band interferometric imaging". Astronomy & Astrophysics. 614: A12. arXiv:1802.06086. Bibcode:2018A&A...614A..12M. doi:10.1051/0004-6361/201731471.
  8. Ahad, A. (2009). "Letter to the Editor: 119 Tauri - the second reddest of all naked eye stars". Journal of the British Astronomical Association. 119 (1): 50. Bibcode:2009JBAA..119...50A.
  9. Percy, John R.; Desjardins, Adrien; Yu, Lawrence; Landis, Howard J. (1996). "Small Amplitude Red Variables in the AAVSO Photoelectric Program: Light Curves and Periods". Publications of the Astronomical Society of the Pacific. 108: 139. Bibcode:1996PASP..108..139P. doi:10.1086/133703.
  10. Kiss, L. L.; Szabó, Gy. M.; Bedding, T. R. (2006). "Variability in red supergiant stars: Pulsations, long secondary periods and convection noise". Monthly Notices of the Royal Astronomical Society. 372 (4): 1721. arXiv:astro-ph/0608438. Bibcode:2006MNRAS.372.1721K. doi:10.1111/j.1365-2966.2006.10973.x.
  11. Percy, J. R.; Favaro, E.; Glasheen, J.; Ho, B.; Sato, H. (2008). "Period Changes in Pulsating Red Supergiant Stars: A Science and Education Project". Journal of the American Association of Variable Star Observers. 36 (2): 145. Bibcode:2008JAVSO..36..145P.
  12. "NED Coordinate & Extinction Calculator Results". Retrieved 2019-01-01.
  13. Beavers, W. I; Cadmus, R. R; Eitter, J. J (1982). "Lunar occultation stellar angular diameter measurements. III". The Astronomical Journal. 87: 818. Bibcode:1982AJ.....87..818B. doi:10.1086/113161.
  14. White, N. M (1980). "The occultation of 119 Tauri and the effective temperatures of three M supergiants". The Astrophysical Journal. 242: 646. Bibcode:1980ApJ...242..646W. doi:10.1086/158501.
  15. White, N. M; Kreidl, T. J; Goldberg, L (1982). "An Occultation Angular Diameter in H-Alpha Light". The Astrophysical Journal. 254: 670. Bibcode:1982ApJ...254..670W. doi:10.1086/159778.
  16. Quirrenbach, A; Mozurkewich, D; Armstrong, J. T; Buscher, D. F; Hummel, C. A (1993). "Angular diameter measurements of cool giant stars in strong TiO bands and in the continuum". The Astrophysical Journal. 406: 215. Bibcode:1993ApJ...406..215Q. doi:10.1086/172432.
  17. Dyck, H. M; Benson, J. A; Van Belle, G. T; Ridgway, S. T (1996). "Radii and Effective Temperatures for K and M Giants and Supergiants". The Astronomical Journal. 111: 1705. Bibcode:1996AJ....111.1705D. doi:10.1086/117910.
  18. Dyck, H. M; Van Belle, G. T; Thompson, R. R (1998). "Radii and Effective Temperatures for K and M Giants and Supergiants. II". The Astronomical Journal. 116 (2): 981. Bibcode:1998AJ....116..981D. CiteSeerX 10.1.1.24.1889. doi:10.1086/300453.
  19. 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.
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