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Date: 21 Sep 93 13:40:00 EST From: "STARS::HRSSHORE" <HRSSHORE%STARS.decnet@hrs.gsfc.nasa.gov> Subject: N Sgr 1993 IUE observations:20/9/93 Steve Shore (IU South Bend) and Sumner Starrfield (ASU) report observations of N Sgr 1993 with IUE. Low resolution spectra were obtained on Sep. 20.5 UT -- exposure times were 2 min (LWP) and 25 min (SWP). The spectrum is still dominated by the iron curtain, but there has been a substantial increase in the flux shortward of 1700 A since the first Vilspa observation on Sep. 17.4 (approx). The continuum is more extinguished by absorption shortward of 1600 A than for Cyg 1992 at the same stage and the pseudo-emission (curtain breaks) features are not as strong. The column density appears higher and the temperature somewhat lower for Sgr 1993 than for Cyg 1992 at the same stage. We also obtained a high resolution (R=10000) spectrum with the LWP camera (2400 - 3200 A). The Mg II 2800 is strong and asymmetric, with a red wing extending to 3500 km/s (the emission extends to -1000 km/s on the steeper blue side). Al II 2640 is also in emission. The spectrum is very similar to the Cyg 1992 observation taken about 5 days after UV minimum, with the marked absence of P Cyg absorption in the Sgr 1993 spectrum being the most obvious exception. On the basis of the exposure times for the Vilspa data, and predictions based on the Cyg 1992 UV light curve, it appears that the observation of 17 Sep. was at UV minimum, just at the end of the fireball stage. The spectrum obtained yesterday indicates that the nova should continue to brighten for the next week in the UV. Observations with IUE will take place on Sep. 23.5 and Sep. 24.5UT. Any spectrophotometry at the same times would be much appreciated. Contact Steve Shore via the network or at (219)237-4401 for more information. Spectrum JD F(integrated) LWP 26428 9251.007 5.63e-10 2400-3200 A SWP 48694 9251.037 3.58e-11 1200-2000 A
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