NEAR-ULTRAVIOLET EXCESS IN SLOWLY ACCRETING T TAURI STARS: LIMITS IMPOSED BY CHROMOSPHERIC EMISSION

被引：74

作者：

Ingleby, Laura ^{[1
]}

Calvet, Nuria ^{[1
]}

Bergin, Edwin ^{[1
]}

Herczeg, Gregory ^{[2
]}

Brown, Alexander ^{[3
]}

Alexander, Richard ^{[4
]}

Edwards, Suzan ^{[5
]}

Espaillat, Catherine ^{[6
]}

France, Kevin ^{[3
]}

Gregory, Scott G. ^{[7
]}

Hillenbrand, Lynne ^{[7
]}

Roueff, Evelyne ^{[8
,9
]}

Valenti, Jeff ^{[10
]}

Walter, Frederick ^{[11
]}

Johns-Krull, Christopher ^{[12
]}

Brown, Joanna ^{[6
]}

Linsky, Jeffrey ^{[13
,14
]}

McClure, Melissa ^{[1
]}

Ardila, David ^{[15
]}

Abgrall, Herve ^{[8
,9
]}

Bethell, Thomas ^{[1
]}

Hussain, Gaitee ^{[16
]}

Yang, Hao ^{[13
,14
]}

机构：

[1] Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA

[2] Max Planck Inst Extraterr Phys, D-85741 Garching, Germany

[3] Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA

[4] Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England

[5] Smith Coll, Dept Astron, Northampton, MA 01063 USA

[6] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA

[7] CALTECH, Dept Astrophys, Pasadena, CA 91125 USA

[8] Observ Paris, CNRS, UMR 8102, Sect Meudon, F-92195 Meudon, France

[9] LUTH, F-92195 Meudon, France

[10] Space Telescope Sci Inst, Baltimore, MD 21218 USA

[11] SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA

[12] Rice Univ, Dept Phys & Astron, Houston, TX 77005 USA

[13] Univ Colorado, JILA, Boulder, CO 80309 USA

[14] NIST, Boulder, CO 80309 USA

[15] CALTECH, NASA Herschel Sci Ctr, Pasadena, CA 91125 USA

[16] ESO, D-85748 Garching, Germany

来源：

ASTROPHYSICAL JOURNAL | 2011年 / 743卷 / 02期

基金：

美国国家科学基金会;

关键词：

accretion; accretion disks; circumstellar matter; stars: pre-main sequence; PRE-MAIN-SEQUENCE; ETA-CHAMAELEONTIS CLUSTER; X-RAY-RADIATION; LOW MASS STARS; FAR-ULTRAVIOLET; CIRCUMSTELLAR DISKS; MAGNETOSPHERIC ACCRETION; INFRARED SPECTROGRAPH; BROWN DWARFS; H-2; EMISSION;

D O I：

10.1088/0004-637X/743/2/105

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Young stars surrounded by disks with very low mass accretion rates are likely in the final stages of inner disk evolution and therefore particularly interesting to study. We present ultraviolet (UV) observations of the similar to 5-9 Myr old stars RECX-1 and RECX-11, obtained with the Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph on the Hubble Space Telescope, as well as optical and near-infrared spectroscopic observations. The two stars have similar levels of near-UV emission, although spectroscopic evidence indicates that RECX-11 is accreting and RECX-1 is not. The line profiles of Ha and He I lambda 10830 in RECX-11 show both broad and narrow redshifted absorption components that vary with time, revealing the complexity of the accretion flows. We show that accretion indicators commonly used to measure mass accretion rates, e. g., U-band excess luminosity or the Ca ii triplet line luminosity, are unreliable for low accretors, at least in the middle K spectral range. Using RECX-1 as a template for the intrinsic level of photospheric and chromospheric emission, we determine an upper limit of 3 x 10(-10) M-circle dot yr(-1) for RECX-11. At this low accretion rate, recent photoevaporation models predict that an inner hole should have developed in the disk. However, the spectral energy distribution of RECX-11 shows fluxes comparable to the median of Taurus in the near-infrared, indicating that substantial dust remains. Fluorescent H2 emission lines formed in the innermost disk are observed in RECX-11, showing that gas is present in the inner disk, along with the dust.

引用

页数：11

共 95 条

[1] Photoevaporation of circumstellar disks due to external far-ultraviolet radiation in stellar aggregates [J].