A visual band light curve for AA Tauri, adapted from Bouvier et al. (2013). [1] The main plot shows the long term variation, and the inset plot shows the periodic variation after the dramatic dimming in 2011. | |
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
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
mas/
yr
[2] Dec.: −20.680 mas/ yr [2] |
Parallax (π) | 7.4255 ± 0.0868 mas [2] |
Distance | 439 ± 5
ly (135 ± 2 pc) |
Details | |
Mass | 0.76 [6] M☉ |
Radius | 1.81 [6] R☉ |
Luminosity | 0.8 [6] L☉ |
Temperature | 4,060 [6] K |
Rotational velocity (v sin i) | 12.8±1.1 [5] km/s |
Age | 2.4 [6] Myr |
Other designations | |
Database references | |
SIMBAD | data |
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]
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". [8] The periodic variations are ascribed to eclipses of the star by a warped dust disk around it. [9]
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. [1]
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. [8] 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 find no evidence for a planet, instead finding multiple rings with accretion streams between them. [9]