Analysis of the HST UV Spectrum of the hot-Am Star HR3383
Abstract
The analysis of high-resolution ultraviolet spectra of the hot-Am star HR 3383 (A1Vm), obtained with the Hubble Space Telescope (HST), is presented. Two datasets were analyzed: the spectral region 160 nm to 190 nm, which was obtained with the Goddard High Resolution Spectrograph (GHRS), and the region 212 nm to 288 nm, which was obtained with the Space Telescope Imaging Spectrograph (STIS). Use of the ultraviolet spectral region is critical to determining the chemical composition of B and A type stars due to the presence of many strong lines of heavy elements. When observed at high resolution, the spectrum of HR 3383 represents a transition object between late-B type HgMn stars (characterized by strong lines of the heaviest elements but little evidence of lanthanide spectra) and Am type stars (showing little evidence of the heaviest elements but a more obvious presence of the lanthanides). The identification of lines from certain heavy elements, for example Lu and Bi, was conducted using measurements of hyperfine structure from our laboratory data. Nearly all lanthanide elements are identified through lines of their third spectrum. Element abundances were determined by fitting the HST spectra with synthetic spectra and resulted in enhancements over the respective solar system value for a number of heavy elements, including Pt, Au, Hg and Bi, by between one and two orders of magnitude. The spectrum of HR 3383 is compared with the HST GHRS spectrum of Sirius (A1 Vm). The higher projected equatorial rotational velocity of Sirius (vsini = 16 km/sec) over that of HR 3383 (vsini = 6 km/sec) results in problematic line blending for abundance analyses. The element abundance distribution for HR 3383 is compared with those of HgMn and Am type stars.
- Publication:
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American Astronomical Society Meeting Abstracts #213
- Pub Date:
- January 2009
- Bibcode:
- 2009AAS...21340805W