Modelling the Hubble Space Telescope Ultraviolet and Optical Spectrum of Spot 1 on the Circumstellar Ring of SN 1987A

Abstract

We report and interpret HST/STIS long-slit observations of the optical and ultraviolet (1150 - 10270 Angstrom) emission-line spectra of the rapidly brightening Spot 1 on the equatorial ring of SN 1987A between 1997 September and 1999 October (days 3869 -- 4606 after outburst). The emission is caused by radiative shocks created where the supernova blast wave strikes dense gas protruding inward from the equatorial ring. We measure and tabulate line identifications, fluxes and, in some cases, line widths and shifts. We compute flux correction factors to account for substantial interstellar line absorption of several emission lines. Nebular analysis shows that optical emission lines come from a region of cool (T_e ~ 10^4 K) and dense (n_e ~ 10^6 cm^-3) gas in the compressed photoionized layer behind the radiative shock. The observed line widths indicate that only shocks with shock velocities V_s < 250 km/s have become radiative, while line ratios indicate that much of the emission must have come from yet slower (V_s < 135 k/ms) shocks. We are able to fit the UV fluxes with an idealized radiative shock model consisting of two shocks (V_s = 135 and 250 km/s). The observed UV flux increase with time can be explained by the increase in shock surface areas as the blast wave overtakes more of the protrusion. The observed flux ratios of optical to highly-ionized UV lines are greater by a factor of ~ 2 -- 3 than predictions from the radiative shock models and we discuss the possible causes. We also present models for the observed H-alpha line widths and profiles, which suggests that a chaotic flow exists in the photoionized regions of these shocks. We discuss what can be learned with future observations of all the spots present on the equatorial ring.

arXiv comment67 pages, 21 figures. Accepted for publication in the Astrophysical Journal

References in corpus (19)

• Correcting for the Effects of Interstellar Extinction
• Radiation hydrodynamics of SN 1987A: I. Global analysis of the light curve for the first 4 months
• Preliminary Spectral Analysis of the Type II Supernova 1999em
• The Line Emission from the Circumstellar Gas Around SN 1987A
• The X-ray Remnant of SN1987A
• Spatially Resolved STIS Spectroscopy of SN 1987A: Evidence for Shock Interaction with Circumstellar Gas
• The asymmetric radio remnant of SN 1987A
• Evolution of the Radio Remnant of SN 1987A: 1990 -- 2001
• Monitoring the Evolution of the X-ray Remnant of SN 1987A
• The evolution of ultraviolet emission lines from the circumstellar material surrounding SN 1987A
• On the Emergence and Discovery of Hot Spots in Supernova Remnant 1987A
• Young Stellar Populations Around SN1987A
• SN 1987A's Circumstellar Envelope, II: Kinematics of the Three Rings and the Diffuse Nebula
• New HST Observations of High Velocity Lyman Alpha and Balmer Alpha in SNR 1987A
• Hubble Space Telescope Spectroscopic Observations of the Ejecta of SN 1987A at 2000 Days
• HST Spectroscopy of Spot 1 on the Circumstellar Ring of SN 1987A
• Physical Conditions in Circumstellar Gas surrounding SN 1987A 12 Years After Outburst
• Analysis of the Type IIn Supernova 1998S: Effects of Circumstellar Interaction on Observed Spectra
• Flash ionization of the partially ionized wind of the progenitor of SN 1987A

Cited by in corpus (36)

• Cassiopeia A and its Clumpy Presupernova Wind
• The jet-powered optical nebula of Cygnus X-1
• SN 1987A After 18 Years: Mid-Infrared GEMINI and SPITZER Observations of the Remnant
• X-ray illumination of the ejecta of Supernova 1987A
• The 3-D Structure of SN 1987A's inner Ejecta
• Abundances and density structure of the inner circumstellar ring around SN 1987A
• The Destruction of the Circumstellar Ring of SN 1987A
• And in the Darkness Bind Them: Equatorial Rings, B[e] Supergiants, and the Waists of Bipolar Nebulae
• The X-ray Spectrum of Supernova Remnant 1987A
• Infrared and X-Ray Evidence for Circumstellar Grain Destruction by the Blast Wave of Supernova 1987A
• Ejecta, Dust, and Synchrotron Radiation in B0540-69.3: A More Crab-Like Remnant than the Crab
• High-Resolution X-ray Spectroscopy of SNR 1987A: Chandra LETG and HETG Observations in 2007
• X-Ray, UV, and Optical Observations of Supernova 2006bp with Swift: Detection of Early X-Ray Emission
• Time evolution of the line emission from the inner circumstellar ring of SN 1987A and its hot spots
• Late Spectral Evolution of the Ejecta and Reverse Shock in SN1987A
• HST-COS Observations of Hydrogen, Helium, Carbon and Nitrogen Emission from the SN 1987A Reverse Shock
• Chandra LETG Observations of Supernova Remnant 1987A
• Fourier Modeling of the Radio Torus Surrounding Supernova 1987A
• Infrared Continuum and Line Evolution of the Equatorial Ring around SN 1987A
• Chandra Observations of Shock Kinematics in Supernova Remnant 1987A
• Observing Supernova 1987A with the Refurbished Hubble Space Telescope
• The matter beyond the ring: the recent evolution of SN 1987A observed by the Hubble Space Telescope
• Multi-dimensional simulations of the expanding supernova remnant of SN 1987A
• Evolution of the Chandra CCD Spectra of SNR 1987A: Probing the Reflected-Shock Picture
• Thirty years of SN 1980K: Evidence for light echoes
• The Nature of the Ultraluminous Oxygen-Rich Supernova Remnant in NGC 4449
• Evolution of the Reverse Shock Emission from SNR 1987A
• ALMA-resolved salt emission traces the chemical footprint and inner wind morphology of VY CMa
• Thermal Emission and Radioactive Lines, but No Pulsar, in the Broadband X-Ray Spectrum of Supernova 1987A
• The reverse shock of SNR1987A at 18 years after outburst
• Coronal emission from the shocked circumstellar ring of SN 1987A
• Spectral Evolution of the X-Ray Remnant of SN 1987A: A High-Resolution $Chandra$ HETG Study
• Optical observations of the young supernova remnant SNR 0540-69.3 and its pulsar
• First VLBI Detection of the Radio Remnant of Supernova 1987A: Evidence for Small-scale Features
• Mapping High-velocity H-alpha and Lyman-alpha Emission from Supernova 1987A
• The morphology of the ejecta of SN 1987A at 31 years from 1150 to 10000 Å