ACCRETION ONTO LOW-MASS STARS AND BROWN DWARFS
- Method: Measure the accretion luminosity from the hydrogen Paschen and Balmer continua emission in
low-resolution spectroscopy with Keck
- Lowest accretion rate measured (2e-12 Msun/yr) onto the TWA brown dwarf 2MASS J1207-3932
- Accretion rates are 3-5 times larger than those measured from models of the H-alpha line profile
- Heated photosphere may be cooler, less dense to smaller accretion rates
WARM GAS IN IRRADIATED DISKS
- Method: High-resolution spectroscopy to confirm disk origin and determine formation radius from line widths with
HST and Gemini North
-
[Ne II] 12.8 micron emission forms in the disk around TW Hya
- FUV H2 emission may form at the disk surface or in the base of outflows
- H2 line opacities indicate a temperature of 2500 K
ACCRETION-POWERED OUTFLOWS FROM YOUNG STARS
- Method: Measuring wind-absorption features in high-resolution far-ultraviolet spectra with HST and FUSE
- No hot coronal wind is detectable: some other outflow must carry away the angular momentum from accretion
- Far-ultraviolet wind absorption is consistent with 10,000 K gas with some photoionization
OTHER ONGOING PROGRAMS
- Photoevaporation of protoplanetary disks
- Irradiation of transition disks
- Evolution of UV and X-ray emissions with mass and with accretion rate
- Production of FUV and X-ray emission from the accretion shock
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UV Excess Measures of Accretion onto Low-mass Stars and Brown Dwarfs. Herczeg, G.J., & Hillenbrand,
L.A.
Submitted to ApJ
High-resolution Spectroscopy of [Ne II] Emission from TW Hya. Herczeg, G.J., Najita, J.R., Hillenbrand,
L.A.,
& Pascucci, I. 2007, ApJ, in press
Observational Constraints on Disk Photoevaporation by the Central Star. Herczeg, G.J., 2007, Proc. of
IAU
Symp. 243, Star-Disk Interactions in Young Stars, eds. J. Bouvier & I. Appenzeller. Not Refereed.
How Hot is the Wind from TW Hydrae? Johns-Krull, C.M., & Herczeg, G.J. 2007, ApJ, 655, 345
The Origins of Fluorescent H2 Emission From T Tauri Stars. Herczeg, G.J., Linsky, J.L., Walter, F.M.,
Gahm, G.F., & Johns-Krull, C.M. 2006, ApJS, 165, 256
Complete
List of Refereed Papers (ADS)
TEACHING EXPERIENCE
Univ. of Colorado at Boulder: ASTR 1110: General Astronomy - Solar System
EDUCATION
2005-present: Postdoctoral Scholar at Caltech. Advisor: Lynne
Hillenbrand
Ph.D., Astrophysics: August 2005, Univ. of Colorado. Advisor: Jeff Linsky
B.S., Physics and Honors Mathematics, 1999, University of Notre Dame
OTHER ACTIVITIES
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