The Evolution of Ultraviolet Emission Lines From Circumstellar Material Surrounding SN 1987A

Abstract

The presence of narrow high-temperature emission lines from nitrogen-rich gas close to SN 1987A has been a principal observational constraint on the evolutionary status of the supernova's progenitor. A new analysis of the complete five-year set of low and high resolution IUE ultraviolet spectra of SN 1987A (1987SN 1987A ( .2-19923) provide fluxes for the N V λ1240, N IV] λ1486, He II λ1640, O III] λ1665, N III] λ1751, and C III] λ1908 lines with significantly reduced random and systematic errors and reveals significant short-term fluctuations in the light curves. The N V , N IV] , and N III] lines turn on sequentially over 15 to 20 days and show a progression from high to low ionization potential, implying an ionization gradient in the emitting region. The line emission turns on suddenly at 83 ± 4 days after the explosion, as defined by N IV] . The N III] line reaches peak luminosity at 399 ± 15 days. A ring radius of (6.24 ± 0.20) × 10 17 cm and inclination of 41. • 0 ± 3. • 9 is derived from these times, assuming a circular ring. The probable role of resonant scattering in the N V light curve introduces -2systematic errors that leads us to exclude this line from the timing analysis. A new nebular analysis yields improved CNO abundance ratios of N/C= 6.1 ± 1.1 and N/O= 1.7 ± 0.5, confirming the nitrogen enrichment found in our previous paper. From the late-time behavior of the light curves we find that the emission originates from progressively lower density gas and that the emitting region has a multi-component density structure. We estimate the emitting mass near maximum (∼ 400 days) to be ∼ 4.7 × 10 −2 M ⊙ , assuming a filling factor of unity and an electron density of 2.6 × 10 4 cm −3 . These results are discussed in the context of current models for the emission and hydrodynamics of the ring.

Probing Elemental Abundances in SNR 1987A usingXMM‐Newton

“…Fransson et al (1989) found N/O ¼ 1:6 AE 0:8, about 12 times higher 3 than the AG89 solar value, which they interpret as evidence of substantial CNO processing. Lundqvist & Fransson (1996) found N/O ¼ 1:1 AE 0:4, while Sonneborn et al (1997) found N/O ¼ 1:7 AE 0:5. All three of these values were derived from optical/ultraviolet data.…”

Infrared Echoes Reveal the Shock Breakout of the Cas A Supernova

“…A flash of EUV-UV shock breakout radiation has been predicted by hydrodynamical simulations of SN explosions (Klein & Chevalier 1978;Falk 1978); however, because it lasts for only a few days, it has only recently been directly observed in a SN. Its existence was first indirectly inferred in SN 1987A from the detection of narrow UV and optical emission lines from the SN Sonneborn et al 1997). The lines arise from an equatorial ring, located about 0.7 lt-yr from the SN and produced by mass loss from the progenitor star that was flashionized by the EUV burst.…”

The age of globular clusters

“…These distance measures include the use of Cepheid variable period-luminosity relations [17,18], or SN 1987A light echoes [19,20].…”

“…This was long before I knew much at all about the detailed issues associated with fitting the main sequence turn-off magnitudes. At the time I was at Yale University, and my colleague in the Astronomy Department there, Pierre Demarque, was using the new Yale isochrones and finding good agreement with ages for the oldest globular clusters in the range [16][17][18][19][20] Gyr. Pierre suggested that this number was accurate to perhaps 20 %, although he felt that this could just as likely result in longer ages rather than shorter ones.…”