Anomalous X-ray line ratios in the cTTS TW hydrae

被引：16
作者：
Ness, JU
Schmitt, JHMM
机构：
[1] Univ Oxford, Dept Phys, Rudolf Peierls Ctr Theoret Phys, Oxford OX1 3NP, England
[2] Univ Hamburg, Hamburger Sternwarte, D-21029 Hamburg, Germany
来源：
ASTRONOMY & ASTROPHYSICS | 2005年 / 444卷 / 02期
关键词：
X-rays : stars; stars : individual : TW Hya; stars : pre-main sequence; stars : coronae; stars : activity; accretion;
D O I：
10.1051/0004-6361:200500208
中图分类号：
P1 [天文学];
学科分类号：
0704 ;
摘要：
The cTTS TW Hya has been observed with high-resolution X-ray spectro solution spectrometers. Previously found high densities inferred from He-like meters. f/i triplets strongly suggested the detected X-ray emission to be dominated by an accretion shock. Because of their radiation field dependence He-like f/i ratios do not provide unambiguous density diagnostics. Here we present additional evidence for high densities from ratios of present Fe XVII lines. Key Fe XVII line ratios in TW Hya deviate from theoretical expectations at low densities as well as from the same measurements in a large sample of stellar coronae. However, a quantitative assessment of densities is difficult because of atomic physics uncertainties. In addition, estimates of low optical depth in line ratios sensitive to resonance scattering effects also support a high-density emission scenario in the X-ray emitting regions of cTTS.
引用
收藏
页码：L41 / L44
页数：4
相关论文
共 17 条
[1]   ABUNDANCES OF THE ELEMENTS - METEORITIC AND SOLAR [J].
ANDERS, E ;
GREVESSE, N .
GEOCHIMICA ET COSMOCHIMICA ACTA, 1989, 53 (01) :197-214
[2]   PHOTOELECTRIC ABSORPTION CROSS-SECTIONS WITH VARIABLE ABUNDANCES [J].
BALUCINSKACHURCH, M ;
MCCAMMON, D .
ASTROPHYSICAL JOURNAL, 1992, 400 (02) :699-700
[3]   Resonance scattering of Fe XVII X-ray and extreme-ultraviolet lines [J].
Bhatia, AK ;
Saba, JLR .
ASTROPHYSICAL JOURNAL, 2001, 563 (01) :434-450
[4]   Diagnostic utility of the relative intensity of 3C to 3D in Fe XVII [J].
Brown, GV ;
Beiersdorfer, P ;
Chen, H ;
Chen, MH ;
Reed, KJ .
ASTROPHYSICAL JOURNAL, 2001, 557 (01) :L75-L78
[5]   High-energy processes in young stellar objects [J].
Feigelson, ED ;
Montmerle, T .
ANNUAL REVIEW OF ASTRONOMY AND ASTROPHYSICS, 1999, 37 :363-408
[6]   INTERPRETATION OF SOLAR HELIUM-LIKE ION LINE INTENSITIES [J].
GABRIEL, AH ;
JORDAN, C .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1969, 145 (02) :241-&
[7]   Indirect X-ray line-formation processes in iron L-shell ions [J].
Gu, MF .
ASTROPHYSICAL JOURNAL, 2003, 582 (02) :1241-1250
[8]   Evidence for accretion: High-resolution X-ray spectroscopy of the classical T Tauri star TW Hydrae [J].
Kastner, JH ;
Weintraub, DA .
ASTROPHYSICAL JOURNAL, 2002, 567 (01) :434-440
[9]   First application of the Fe XVII I(17.10Å)/I(17.05Å) line ratio to constrain the plasma density of a cosmic X-ray source [J].
Mauche, CW ;
Liedahl, DA ;
Fournier, KB .
ASTROPHYSICAL JOURNAL, 2001, 560 (02) :992-996
[10]   On the sizes of stellar X-ray coronae [J].
Ness, JU ;
Güdel, M ;
Schmitt, JHMM ;
Audard, M ;
Telleschi, A .
ASTRONOMY & ASTROPHYSICS, 2004, 427 (02) :667-+
12