Astronomy:IK Tauri

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Short description: Mira variable star in the constellation Taurus
IK Tauri
IKTauLightCurve.png
A visual band light curve for IK Tauri, plotted from ASAS-SN data.[1] The main plot shows the brightness as a function of time, and the inset shows the same data plotted as a function of pulsation phase.
Observation data
Equinox J2000.0]] (ICRS)
Constellation Taurus
Right ascension  03h 53m 28.87s[2]
Declination +11° 24′ 21.7″[2]
Apparent magnitude (V) 10.8 - 16.5[3]
Characteristics
Evolutionary stage Asymptotic giant branch
Spectral type M6e - M10e[3]
Apparent magnitude (K) −1.24[4]
U−B color index −0.04[4]
B−V color index +3.64[4]
Variable type Mira[3]
Astrometry
Radial velocity (Rv)~46[5] km/s
Proper motion (μ) RA: 32.806±0.799[6] mas/yr
Dec.: −22.820±0.663[6] mas/yr
Parallax (π)3.5114 ± 0.3496[6] mas
Distance930 ± 90 ly
(280 ± 30 pc)
Details
Mass1 - 1.5[7] M☉
Radius608 ± 66[7] R☉
Luminosity8,724±1,921[7] L☉
Surface gravity (log g)–0.95[7] cgs
Temperature2,234±86[7] K
Other designations
IK Tau, NML Tauri, 2MASS J03532886+1124216, IRAS 03507+1115, AAVSO 0347+11
Database references
SIMBADdata

IK Tauri or NML Tauri is a Mira variable star located about 280 parsecs (910 ly) from the Sun in the zodiac constellation of Taurus.[7]

Discovery

In 1965, Neugebauer, Martz, and Leighton, astronomers with the California Institute of Technology, reported the discovery of two extremely cool stars. At the time, the temperatures of these extremely red objects were estimated to be around 1,000 K.[8]

In the absence of other designations, these were named after the initials of their discoverers as NML Cygni and NML Tauri.[9][10] It was identified as a Mira variable in 1967.[11] The name NML Tauri fell into disuse after the star received its variable star designation of IK Tauri.[12]

Variability

IK Tauri varies approximately every 470 days between extreme visual magnitudes of 10.8 and 16.5.[3] It was classified as a Mira variable soon after discovery on the basis of its spectrum showing strong hydrogen emission and its very large visual amplitude.[11] During each cycle, the spectrum of the star also varies, consistently reaching M10 near minimum and only M6-M8 at maximum.[3]

Properties

IK Tauri pulsates strongly every 470 days, being coolest and largest at minimum brightness. The bolometric luminosity varies less dramatically and is estimated to be 8,724 L☉. The temperature is calculated to be only 2,234 K, and the radius is calculated to be 608 R☉.

IK Tauri has strong maser emission from its extended atmosphere and circumstellar material.[13] The circumstellar material is rich in dust, with alumina close to the star and silicates further out. The two types of dust form separate shells, one within twice the star's radius and one more than three times its radius. The densest region of dust is at 6-8 times IK Tauri's radius.[14]

Although IK Tauri is far below naked eye visibility, even at maximum brightness, this is due to the low temperature and strong extinction at visual wavelengths. In the infrared, it is brighter than prominent stars such as Rigel (K-band magnitude +0.18[4]) and comparable to Sirius (K-band magnitude −1.35[4]).[14]

Evolution

As a Mira variable, IK Tauri is an asymptotic giant branch (AGB) star, originally around 1.5 M☉.[15] It has exhausted its core hydrogen and helium, is not massive enough to ignite its carbon-oxygen core, and is now alternately fusing in concentric hydrogen and helium shells. As the inert core grows and the hydrogen shell nears the surface, mass loss becomes very high, and the star becomes highly obscured visually, an infrared star.[16] It will then quickly lose its entire atmosphere, creating a planetary nebula and leaving behind a white dwarf.


References

  1. ↑ "ASAS-SN Variable Stars Database". ASAS-SN. https://asas-sn.osu.edu/variables/lookup. 
  2. ↑ 2.0 2.1 Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E. et al. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues 2246: II/246. Bibcode: 2003yCat.2246....0C. http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=II/246. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Samus, N. N. 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. Bibcode: 2009yCat....102025S. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 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. ↑ Feast, Michael W.; Whitelock, Patricia A. (2000). "Mira kinematics from Hipparcos data: A Galactic bar to beyond the Solar circle". Monthly Notices of the Royal Astronomical Society 317 (2): 460. doi:10.1046/j.1365-8711.2000.03629.x. Bibcode: 2000MNRAS.317..460F. 
  6. ↑ 6.0 6.1 6.2 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 Adam, C.; Ohnaka, K. (2019). "Exploring the innermost dust formation region of the oxygen-rich AGB star IK Tauri with VLT/SPHERE-ZIMPOL and VLTI/AMBER". Astronomy & Astrophysics 628: A132. doi:10.1051/0004-6361/201834999. Bibcode: 2019A&A...628A.132A. 
  8. ↑ Neugebauer, G.; Martz, D. E.; Leighton, R. B. (1965). "Observations of Extremely Cool Stars". Astrophysical Journal 142: 399. doi:10.1086/148300. Bibcode: 1965ApJ...142..399N. https://authors.library.caltech.edu/74594/1/1965ApJ___142__399N.pdf. 
  9. ↑ Kruszewski, A. (1968). "Infrared Objects: Wavelength Dependence of Polarization". Publications of the Astronomical Society of the Pacific 80 (476): 560. doi:10.1086/128685. Bibcode: 1968PASP...80..560K. 
  10. ↑ Wyckoff, S.; Wehinger, P. (1973). "Revised period and minimum-light spectrum of NML Tauri". Astrophysical Journal 186: 989. doi:10.1086/152562. Bibcode: 1973ApJ...186..989W. 
  11. ↑ 11.0 11.1 Wing, Robert F.; Spinrad, Hyron; Kuhi, L. V. (1967). "Infrared Stars". Astrophysical Journal 147: 117. doi:10.1086/148985. Bibcode: 1967ApJ...147..117W. 
  12. ↑ Wing, R. F.; Lockwood, G. W. (1973). "The period and spectral range of IK Tauri". Astrophysical Journal 184: 873. doi:10.1086/152376. Bibcode: 1973ApJ...184..873W. 
  13. ↑ Cotton, W. D.; Ragland, S.; Danchi, W. C. (2011). "Polarized Emission from SiO Masers in IK Tauri". The Astrophysical Journal 736 (2): 96. doi:10.1088/0004-637X/736/2/96. Bibcode: 2011ApJ...736...96C. 
  14. ↑ 14.0 14.1 Gobrecht, D.; Cherchneff, I.; Sarangi, A.; Plane, J. M. C.; Bromley, S. T. (2016). "Dust formation in the oxygen-rich AGB star IK Tauri". Astronomy & Astrophysics 585: A6. doi:10.1051/0004-6361/201425363. Bibcode: 2016A&A...585A...6G. 
  15. ↑ Decin, L.; De Beck, E.; Brünken, S.; Müller, H. S. P.; Menten, K. M.; Kim, H.; Willacy, K.; De Koter, A. et al. (2010). "Circumstellar molecular composition of the oxygen-rich AGB star IK Tauri. II. In-depth non-LTE chemical abundance analysis". Astronomy and Astrophysics 516: A69. doi:10.1051/0004-6361/201014136. Bibcode: 2010A&A...516A..69D. 
  16. ↑ Wilson, W. J.; Barrett, A. H. (1972). "Characteristics of OH emission from infrared stars". Astronomy and Astrophysics 17: 385. Bibcode: 1972A&A....17..385W. 



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