The Spectrum of Supernova 1987A

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other, more subtle, changes as broadspectral features appear and fade as theionization conditions in the atmospherechange. Because they are so broad,

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are also becoming stronger as the vol-ume of the emitting gas increases andthe temperature of the absorbing col-umn decreases (Fig. 1b). There are

Figure 1: Spectra of 1987A, obtained by J. Oanziger and R. Fosbury al Ihe ESO 3.6-mtelescope with the Boiler and Chivens spectrograph. The upper spectrum (a) was obtained onFebruary 27.05, four days after the explosion and already shows the strong P Cyg profilesmentioned in. the text. The lower spectrum (b), although qualitatively similar, displays importanlchanges in the amplitude and also in the velocities of the main features.

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these features are notoriously difficult toattribute to different chemical elementsbut it appears likely that the strongest ofthem can be identified with singlyionized calcium and iron. When the opti-cal and infrared data are combined, thetemperature of the "black-body" con-tinuum is readily measured; it was5900 K on the night of 1-2 March (seethe plot of the infrared - optical photo-metry). The fact that this temperature

was higher in the initial phase was goodnews for the IUE for wh ich the superno-va now provides a greatly weakenedsource.

Another aspect of the spectroscopywhich is causing great excitement is thepossibility such a bright object in theLMC provides for the study of the inter-stellar/intergalactic medium between usand the supernova. Sight lines outsideour own Galaxy have been studied be-

fore, using as background sourcesbright stars in the Magellanic Cloudsand much more distant Quasars andSeyfert galaxies. These, however, arevery faint objects and the opportunitypresented by a naked eye supernovahas already resulted in a Bonanza ofresults from the very high resolutionspectrograph (CAT/CES) at ESO (seecontribution by Andreani, Ferlet andVidal-Madjar). R. Fosbury (ST-ECF)

High-resolution Spectroscopy of 1987A