Physical Conditions in Circumstellar Gas surrounding SN 1987A 12 Years After Outburst

Abstract

Two-dimensional spectra of Supernova 1987A were obtained on 1998 November 14-15 (4282 days after outburst) with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). The slit sampled portions of the inner circumstellar ring at the east and west ansae as well as small sections of both the northern and southern outer rings. The temperature and density at these locations are estimated by nebular analysis of [N II], [O III], and [S II] emission line ratios, and with time-dependent photoionization/recombination models. The results from these two methods are mutually consistent. The electron density in the inner ring is ~ 4000 cm-3 for S II, with progressively lower densities for N II and O III. The electron temperatures determined from [N II] and [O III] line ratios are ~11,000 K and \~22,000 K, respectively. These results are consistent with evolutionary trends in the circumstellar gas from similar measurements at earlier epochs. We find that emission lines from the outer rings come from gas of lower density (n_e \la 2000 cm-3) than that which emits the same line in the inner ring. The N/O ratio appears to be the same in all three rings. Our results also suggest that the CNO abundances in the northern outer ring are the same as in the inner ring, contrary to earlier results of Panagia et al. (1996). Physical conditions in the southern outer ring are less certain because of poorer signal-to-noise data. The STIS spectra also reveal a weak Ha emission redshifted by ~100 km s-1 at p.a. 103\arcdeg that coincides with the recently discovered new regions that are brightening (Lawrence et al. 2000). This indicates that the shock interaction in the SE section of the inner ring commenced over a year before it became apparent in HST images.

25 pages, 6 figures, to appear in December 1, 2000 Astrophysical Journal

References in corpus (5)

• Radiation hydrodynamics of SN 1987A: I. Global analysis of the light curve for the first 4 months
• On the Emergence and Discovery of Hot Spots in Supernova Remnant 1987A
• SN 1987A's Circumstellar Envelope, II: Kinematics of the Three Rings and the Diffuse Nebula
• HST Spectroscopy of Spot 1 on the Circumstellar Ring of SN 1987A
• Physical Conditions in Circumstellar Gas surrounding SN 1987A 12 Years After Outburst

Cited by in corpus (14)

• The X-ray Remnant of SN1987A
• Modelling the Hubble Space Telescope Ultraviolet and Optical Spectrum of Spot 1 on the Circumstellar Ring of SN 1987A
• On the Emergence and Discovery of Hot Spots in Supernova Remnant 1987A
• The young pulsar PSR B0540-69.3 and its synchrotron nebula in the optical and X-rays
• Evolution and Geometry of Hot Spots in Supernova Remnant 1987A
• JWST NIRSpec observations of Supernova 1987A -- from the inner ejecta to the reverse shock
• Physical Conditions in Circumstellar Gas surrounding SN 1987A 12 Years After Outburst
• The outer rings of SN1987A
• Radio Supernova 1987A at 843 MHz
• Optical observations of the young supernova remnant SNR 0540-69.3 and its pulsar
• Properties of the three-dimensional structure in the central region of the supernova remnant SNR 0540-69.3
• Bipolar rings from jet-inflated bubbles around evolved binary stars
• Formation of Double Rings Around Evolved Stars
• Kinematics, structure and abundances of supernova remnant 0540-69.3