D. Baade, European Southern Observatory (ESO); and L. Wang, D. A. Howell, and J. C. Wheeler, University of Texas, report: "SN 1987A was observed on Mar. 2 and 3 with the ESO 3.6-m telescope (+ EFOSC2). A low-resolution spectrum (range 429.9-817.6 nm; resolving power about 1000; p.a. of the slit 220 deg; width of the slit 1") shows dramatic changes of the line profiles compared to those obtained a year earlier. The most remarkable features are: 1) The H-alpha profile is now much broader; the blue wing of the H-alpha line has grown much stronger than a year ago and has now merged with the neighboring [O I] line at 630.0 and 636.4 nm, and is stronger than the same [O I] line; the red wing of H-alpha is also much stronger and broader, being traceable at least to 14 000 km/s. 2) Many new narrow emission lines were detected, which have a spatial extension comparable to that of the inner bright ring. The blobs with the highest S/N ratios appear near H-beta in wavelength and are not seen at H-alpha. They are unresolved at our spectral resolution. At least six distinct narrow features were detected on top of the broad H-beta emission line of the supernova ejecta. Comparison with earlier data suggests that the interaction between the SN 1987A ejecta and its circumstellar material is increasing in strength rapidly. Observations in all accessible wavelength ranges are strongly encouraged."
International Astronomical Union Circular
- Pub Date:
- March 1998