Query : 2013A&A...557A..77B

2013A&A...557A..77B - Astronomy and Astrophysics, volume 557A, 77-77 (2013/9-1)

AA tauri's sudden and long-lasting deepening: enhanced extinction by its circumstellar disk.


Abstract (from CDS):

AA Tau has been monitored for more than 20 years since 1987 and exhibited a nearly constant brightness level of V=12.5mag. We report here that in 2011 it suddenly faded, becoming 2 mag fainter in the V-band, and has remained in this deep state since then. We investigate the origin of the sudden dimming of the AA Tau system. We report on new optical and near-IR photometry and spectroscopy obtained during the fading event. The system appears to be much redder and fainter than it was in the bright state. Moreover, the 8.2d photometric period continuously observed for more than 20 years is not detected during most of the deep state. The analysis of the system's brightness and colors suggests that the visual extinction on the line of sight has increased by about 3-4mag in the deep state. At optical wavelengths, the system appears to be dominated by scattered light, probably originating from the upper surface layers of a highly inclined circumstellar disk. The profiles of the Balmer lines have significantly changed as well, with the disappearance of a central absorption component regularly observed in the bright state. We ascribe this change to the scattering of the system's spectrum by circumstellar dust. Remarkably, the mass accretion rate in the inner disk and onto the central star has not changed as the system faded. We conclude that the deepening of the AA Tau system is due to a sudden increase of circumstellar dust extinction on the line of sight without concomitant change in the accretion rate. We suggest that the enhanced obscuration may be produced by a nonaxisymmetric overdense region in the disk, located at a distance of 7.7AU or more, that was recently brought into the line of sight by its Keplerian motion around the central star.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - stars: individual: AA Tau - stars: pre-main sequence - stars: variables: T Tauri, Herbig Ae/Be

VizieR on-line data: <Available at CDS (J/A+A/557/A77): aatau.dat>

Simbad objects: 6

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Number of rows : 6
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 TYC 1833-574-1 * 04 34 45.1088954016 +24 24 43.152346692   12.57 11.62     G8 7 0
2 2MASS J04344826+2428532 * 04 34 48.2577187272 +24 28 53.169916296           ~ 2 0
3 V* AA Tau Or* 04 34 55.4201902392 +24 28 53.033624580 13.14 13.34 12.20 12.03   K5Ve 714 0
4 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 4263 0
5 NGC 2264 OpC 06 40 52.1 +09 52 37           ~ 1761 0
6 CD-32 5613 WD* 08 41 32.4290850497 -32 56 32.915823461   12.07 11.85 12.3   DA5.5 297 0

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