Astronomy:AA Tauri

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Short description: Star in the constellation Taurus
AA Tauri
Gaia finds hints of planets in baby star systems ESA516220.png
The disk around AA Tauri imaged by ALMA[1]
Observation data
Equinox J2000.0]] (ICRS)
Constellation Taurus
Right ascension  04h 34m 55.42019s[2]
Declination +24° 28′ 53.0336″[2]
Apparent magnitude (V) 12.2 to 16.1[3]
Characteristics
Spectral type K7Ve[4]
Variable type T Tauri-type?[4]
Astrometry
Radial velocity (Rv)16.98±0.04[5] km/s
Proper motion (μ) RA: +5.323[2] mas/yr
Dec.: −20.680[2] mas/yr
Parallax (π)7.4255 ± 0.0868[2] mas
Distance439 ± 5 ly
(135 ± 2 pc)
Details
Mass0.76[6] M☉
Radius1.81[6] R☉
Luminosity0.8[6] L☉
Temperature4,060[6] K
Rotational velocity (v sin i)12.8±1.1[5] km/s
Age2.4[6] Myr
Other designations
AA Tau, GSC 01833-00851, IRAS F04318+2422, 2MASS J04345542+2428531, XEST 25-026, AN 196.1930, CSI+24-04319, MHA 259-17, 2E 0431.8+2422, UBV 4396, 2E 1098, XEST 25-OM-003[7]
Database references
SIMBADdata

AA Tauri is a young variable star in the equatorial constellation of Taurus, located in the Taurus-Auriga star-forming region. It is too faint to view with the naked eye, having an apparent visual magnitude that varies from 12.2 down to 16.1.[3] The star is located approximately 439 light-years (135 parsecs) away from the Sun based on parallax, and is drifting further away with a radial velocity of +17 km/s.[5]

The stellar classification for this object is K7Ve,[4] matching a K-type main-sequence star that displays emission features. It is an eruptive variable of the T Tauri type[3] with an estimated age of 2.4 million years. The object has 76% of the mass of the Sun, 181% of the Sun's radius,[6] and is spinning with a projected rotational velocity of 13 km/s.[5] AA Tauri is radiating 80% of the luminosity of the Sun at an effective temperature of 4,060 K.[6]

Variability

A visual band light curve for AA Tauri, adapted from Bouvier et al. (2013).[8] The main plot shows the long term variation, and the inset plot shows the periodic variation after the dramatic dimming in 2011.

AA Tauri shows brightness variations of one to two magnitudes over an 8.2-day period. The brightness has been described as "roughly constant, interrupted by quasi-cyclic fading episodes".[9] The periodic variations are ascribed to eclipses of the star by a warped dust disk around it.[10]

In 2011, AA Tauri faded by about two magnitudes and has remained at the fainter level since then. The star also became significantly more reddened. The eight-day variations continue, with a maximum brightness now around magnitude 14 and magnitude 16.5 at its faintest. It is theorised that the root cause of this dimness is a warp in the accretion disk, located at a distance of 7.7 AU or more from the centre, that was brought into the line of sight by its elliptical motion around the central star.[8]

Search for companions

In their 2003 paper, Bouvier et al. invoked the possible presence of a substellar object to explain peculiar and periodic eclipses occurring to the young star every 8.3 days, though they considered it unlikely that such a companion could be responsible for said variability.[9] They inferred a mass of 20 times that of Jupiter for the perturbing object and an orbital separation of 0.08 Astronomical Units. Later studies found no evidence for a planet, instead finding multiple rings with accretion streams between them.[10]

Gaia astrometry shows evidence of a proper motion anomaly, suggesting the presence of a stellar companion.[1]

References

  1. ↑ 1.0 1.1 Vioque, Miguel et al. (December 2025). "Astrometric view of companions in the inner dust cavities of protoplanetary discs". Astronomy & Astrophysics. doi:10.1051/0004-6361/202557086. 
  2. ↑ 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 Samus, N. N. et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1 61 (1): 80–88. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  4. ↑ 4.0 4.1 4.2 Herbig, G. H. (1977). "Radial velocities and spectral types of T Tauri stars". Astrophysical Journal 214: 747–758. doi:10.1086/155304. Bibcode: 1977ApJ...214..747H. 
  5. ↑ 5.0 5.1 5.2 5.3 Nguyen, Duy Cuong et al. (February 2012). "Close Companions to Young Stars. I. A Large Spectroscopic Survey in Chamaeleon I and Taurus-Auriga". The Astrophysical Journal 745 (2): 25. doi:10.1088/0004-637X/745/2/119. 119. Bibcode: 2012ApJ...745..119N. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 Güdel (2007). "The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)". Astronomy and Astrophysics 468 (2): 353–377. doi:10.1051/0004-6361:20065724. Bibcode: 2007A&A...468..353G. 
  7. ↑ "AA Tau". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=AA+Tau. 
  8. ↑ 8.0 8.1 Bouvier, J.; Grankin, K.; Ellerbroek, L. E.; Bouy, H.; Barrado, D. (2013). "AA Tauri's sudden and long-lasting deepening: Enhanced extinction by its circumstellar disk". Astronomy & Astrophysics 557: A77. doi:10.1051/0004-6361/201321389. Bibcode: 2013A&A...557A..77B. 
  9. ↑ 9.0 9.1 Bouvier (2003). "Eclipses by circumstellar material in the T Tauri star AA Tau. II. Evidence for non-stationary magnetospheric accretion". Astronomy and Astrophysics 409: 169–192. doi:10.1051/0004-6361:20030938. Bibcode: 2003A&A...409..169B. 
  10. ↑ 10.0 10.1 Loomis, Ryan A.; Öberg, Karin I.; Andrews, Sean M.; MacGregor, Meredith A. (2017). "A Multi-ringed, Modestly Inclined Protoplanetary Disk around AA Tau". The Astrophysical Journal 840 (1): 23. doi:10.3847/1538-4357/aa6c63. Bibcode: 2017ApJ...840...23L. 



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