Spectroscopic Investigation of Companion Stars in Herbig AeBe Binary Systems
Abstract
Herbig AeBe (HAEBE) binary systems are good environments for the study of pre-main sequence stellar evolution in companion stars whose mass may be significantly lower than that of the primary star. Measurements of the spectral type and surface gravity of the companion star in the system allow it to be placed on the H-R diagram, where theoretical evolutionary model tracks can then constrain its mass and age, and comparisons can be made between these low mass stars and those formed without the presence of a high mass star. Because of the extinction associated with objects in star forming regions, the near-infrared offers a less obscured wavelength region than the optical through which to study these objects. Medium (R=1,700 & 6,000) and High (R=18,000) Resolution near-infrared (NIR) spectra were gathered for the analysis of these companion stars. We present two different ways to measure Teff and estimate Log g from the spectra of late type stars, depending on the spectral resolution. At high resolution, detailed model fits to the shapes of the Na lines at 2.2 microns and the (2-0) 12CO bandhead at 2.29 microns provides an accurate way to measure effective temperature and surface gravity, in addition to allowing for values of vsini, veiling, and radial velocity to be estimated. At medium resolution, the equivalent widths of 10 of the strongest absorption lines present in the NIR spectrum were measured to determine Teff at a lower accuracy. Preliminary results show that these techniques are effective for characterizing late-type comparisons. Analysis of two stars is discussed; more data is needed to address statistical questions about the nature of HAEBE companions. This work was supported by the National Science Foundation under grant no. 0353843.
- Publication:
-
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AAS...20910505S