TW Hya: Spectral Variability, X-Rays, and Accretion Diagnostics

Details TW Hya: Spectral Variability, X-Rays, and Accretion Diagnostics TW Hya: Spectral Variability, X-Rays, and Accretion Diagnostics

2012-02-28

arxiv.org/abs/1202.6373v1

Astronomy and Astrophysics

Astrophysics

Solar and Stellar Astrophysics

61 pages; 22 figures; to appear in The Astrophysical Journal

Scientific paper

The nearest accreting T Tauri star, TW Hya was observed with spectroscopic and photometric measurements simultaneous with a long se gmented exposure using the CHANDRA satellite. Contemporaneous optical photometry from WASP-S indicates a 4.74 day period was present during this time. Absence of a similar periodicity in the H-alpha flux and the total X-ray flux points to a different source of photometric variations. The H-alpha emission line appears intrinsically broad and symmetric, and both the profile and its variability suggest an origin in the post-shock cooling region. An accretion event, signaled by soft X-rays, is traced spectroscopically for the first time through the optical emission line profiles. After the accretion event, downflowing turbulent material observed in the H-alpha and H-beta lines is followed by He I (5876A) broadening. Optical veiling increases with a delay of about 2 hours after the X-ray accretion event. The response of the stellar coronal emission to an increase in the veiling follows about 2.4 hours later, giving direct evidence that the stellar corona is heated in part by accretion. Subsequently, the stellar wind becomes re-established. We suggest a model that incorporates this sequential series of events: an accretion shock, a cooling downflow in a supersonically turbulent region, followed by photospheric and later, coronal heating. This model naturally explains the presence of broad optical and ultraviolet lines, and affects the mass accretion rates determined from emission line profiles.

Affiliated with

Also associated with

No associations

Rating

TW Hya: Spectral Variability, X-Rays, and Accretion Diagnostics does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with TW Hya: Spectral Variability, X-Rays, and Accretion Diagnostics, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and TW Hya: Spectral Variability, X-Rays, and Accretion Diagnostics will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-522811