C.D.S. - SIMBAD4 rel 1.7 - 2019.12.07CET09:48:00

2006A&A...455..731I - Astronomy and Astrophysics, volume 455, 731-740 (2006/8-4)

On the ionisation fraction in protoplanetary disks. III. The effect of X-ray flares on gas-phase chemistry.


Abstract (from CDS):

Recent observations of the X-ray emission from T Tauri stars in the Orion nebula have shown that they undergo frequent outbursts in their X-ray luminosity. These X-ray flares are characterised by increases in luminosity by two orders of magnitude, a typical duration of less than one day, and a significant hardening of the X-ray spectrum. It is unknown what effect these X-ray flares will have on the ionisation fraction and dead-zone structure in protoplanetary disks. We present the results of calculations designed to address this question. We have performed calculations of the ionisation fraction in a standard α-disk model using two different chemical reaction networks. We include in our models ionisation due to X-rays from the central star, and calculate the time-dependent ionisation fraction and dead-zone structure for the inner 10AU of a protoplanetary disk model. We find that the disk response to X-ray flares depends on whether the plasma temperature increases during flares and/or whether heavy metals (such as magnesium) are present in the gas phase. Under favourable conditions the outer disk dead-zone can disappear altogether, and the dead-zone located between 0.5<R<2AU can disappear and reappear in phase with the X-ray luminosity. X-ray flares can have a significant effect on the dead-zone structure in protoplanetary disks. Caution is required in interpreting this result as the duration of X-ray bursts is considerably shorter than the growth time of MHD turbulence due to the magnetorotational instability.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - magnetohydrodynamics (MHD) - stars: planetary systems: protoplanetary disks - stars: pre-main sequence

Simbad objects: 3

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Number of rows : 3

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 NAME Tau-Aur Region SFR 04 30 +25.0           ~ 1183 1
2 NAME Trapezium Cluster As* 05 35 16.5 -05 23 14           ~ 1436 1
3 M 42 HII 05 35 17.3 -05 23 28           ~ 3664 0

    Equat.    Gal    SGal    Ecl

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