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Star-Disk Interaction In Herbig Ae/Be Stars, Christa Speights
Star-Disk Interaction In Herbig Ae/Be Stars, Christa Speights
All Theses
The question of the mechanism of certain types of stars is important. Classical T Tauri (CTTS) stars accrete magnetospherically, and Herbig Ae/Be stars (higher-mass analogs to CTTS) are thought to also accrete magnetospherically, but the source of a kG magnetic field is unknown, since these stars have radiative interiors. For magnetospheric accretion, an equation has been derived (Hartmann, 2001) which relates the truncation radius, stellar radius, stellar mass, mass accretion rate and magnetic field strength.
Currently the magnetic field of Herbig stars is known to be somewhere between 0.1 kG and 10 kG. One goal of this research is to …
A Spectro-Astrometric Measurement Of Brackett Gamma Emission In Herbig Ae/Be Stars, Thomas S. Rice, Sean D. Brittain
A Spectro-Astrometric Measurement Of Brackett Gamma Emission In Herbig Ae/Be Stars, Thomas S. Rice, Sean D. Brittain
Publications
In T Tauri stars, the Brackett gamma line strength is a reliable indicator of accretion luminosity. Among intermediate mass young stars, Herbig Ae stars also show this correlation, but in Herbig Be stars the Brgamma line flux significantly overpredicts accretion luminosity. This Brgamma excess in Herbig Be stars is thought to arise from a spatially extended outflow. Using commissioning data from the LUCIFER spectrograph on the 8.4-meter Large Binocular Telescope (LBT), we present a spectro-astrometric study of two Herbig Ae/Be stars, the HAe star MWC480 and the HBe star HD 259431. In both stars, an extended Brgamma source can be …
Co Emission In The Inner Disk Around Young Intermediate-Mass Stars, Matt L. Stevans, Sean D. Brittain
Co Emission In The Inner Disk Around Young Intermediate-Mass Stars, Matt L. Stevans, Sean D. Brittain
Publications
We present observations that indicate viscous heating contributes significantly to the surface heating of the inner disk region (0.1-5 AU) around young intermediate-mass stars, Herbig AeBe stars, when the inner disk is optically thick. Brgamma flux is known to scale with accretion rate around young stars. We find a trend between Brgamma and CO emissivity, a tracer 1, 500 K gas in the gaseous atmospheres of less evolved inner disk regions in a sample of 25 Herbig AeBe stars, the higher mass analog of T Tauri stars. Evolved Herbig circumstellar disks do not follow this trend as closely. A thermal …
Measuring The Stellar Accretion Rates Of Herbig Ae/Be Stars, Brian Donehew, Sean D. Brittain
Measuring The Stellar Accretion Rates Of Herbig Ae/Be Stars, Brian Donehew, Sean D. Brittain
Publications
The accretion rate of young stars is a fundamental characteristic of these systems.While accretion onto T Tauri stars has been studied extensively, little work has been done on measuring the accretion rate of their intermediate-mass analogs, the Herbig Ae/Be stars. Measuring the stellar accretion rate of Herbig Ae/Bes is not straightforward both because of the dearth of metal absorption lines available for veiling measurements and the intrinsic brightness of Herbig Ae/Be stars at ultraviolet wavelengths where the brightness of the accretion shock peaks. Alternative approaches to measuring the accretion rate of young stars by measuring the luminosity of proxies such …