Greg Herczeg

Under Construction: 11/11/07

gregoryh at astro.caltech.edu
(626) 395-4421
Caltech, MC 105-24
1200 E. California Blvd.
Pasadena, CA 91125


CURRICULUM VITAE: pdf
RESEARCH INTERESTS: YOUNG STARS SELECTED RECENT PAPERS (PDF)

  • 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



    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


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