GHRS Spectroscopy of individual stars in R136a

Details GHRS Spectroscopy of individual stars in R136a GHRS Spectroscopy of individual stars in R136a

Nov 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...435l..39h&link_type=abstract

Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 435, no. 1, p. L39-L42

Physics

Optics

27

Magellanic Clouds, Main Sequence Stars, Massive Stars, O Stars, Star Clusters, Stellar Evolution, Stellar Spectrophotometry, Stellar Winds, Ultraviolet Spectra, Emission Spectra, Hubble Space Telescope, Line Spectra, Size Determination, Stellar Luminosity, Stellar Mass, Stellar Models, Stellar Temperature

Scientific paper

The installation of the Corrective Optics Space Telescope Axial Replacement (COSTAR) Instrument on the Hubble Space Telescope (HST) makes it possible to observe stars in very crowded regions with high spatial and spectral purity. To demonstrate this capability, we have used the Goddard High Resolution Spectrograph (GHRS) to obtain spectra of two stars in the dense center of the 30 Doradus ionizing cluster: R136a5, and its nearest neighbor, R136a2, only 0.17 sec away. R136a5 is shown to ben an O3f/WN star, while R136a2 is a WN4-w star. From both Wide Field/Planetary Camera (WFPC) photometry and GHRS, spectroscopy we estimate the following properties of R136a5: Teff = 42,500 K, R = 16.4 solar radius, Lbol = 8 x 105 solar luminosity, and M approx. equals 50 solar mass -- all indicating that, despite its spectral type, R136a5, as indicated by the strength of He II lambda 1640 emission. The observed mass-loss rate, dot-M = 1.8 x 10-5 solar mass/yr, is an order of magnitude higher than is assumed by current stellar evolutionary models. We argue that this high rate of mass loss will alter drastically the evolutionary path of R136a5. If so, evolutionary models for massive stars require substantial revision.

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