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GHRS Spectroscopy of individual stars in R136aThe 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: T(sub eff) = 42,500 K, R = 16.4 solar radius, L(sub bol) = 8 x 10(exp 5) 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(exp -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.
Document ID
19950040556
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Heap, Sara R.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Ebbets, Dennis
(Ball Aerospace Corp. Boulder, CO, United States)
Malumuth, Eliot M.
(Computer Science Corporation Lanham, MD, United States)
Maran, Stephen P.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Koter, Alex DE
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Hubeny, Ivan
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 16, 2013
Publication Date
November 1, 1994
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 435
Issue: 1
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A72155
Funding Number(s)
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other

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