The Matter Beyond the Ring: The Recent Evolution of SN 1987A Observed by the Hubble Space Telescope

Abstract

The nearby SN 1987A offers a spatially resolved view of the evolution of a young supernova (SN) remnant. Here we precent recent Hubble Space Telescope imaging observations of SN 1987A, which we use to study the evolution of the ejecta, the circumstellar equatorial ring (ER) and the increasing emission from material outside the ER. We find that the inner ejecta have been brightening at a gradually slower rate and that the western side has been brighter than the eastern side since ∼ 7000 days. This is expected given that the X-rays from the ER are most likely powering the ejecta emission. At the same time the optical emission from the ER continues to fade linearly with time. The ER is expanding at 680 ± 50 km s −1 , which reflects the typical velocity of transmitted shocks in the dense hotspots. A dozen spots and a rim of diffuse Hα emission have appeared outside the ER since 9500 days. The new spots are more than an order of magnitude fainter than the spots in the ER and also fade faster. We show that the spots and diffuse emission outside the ER may be explained by fast ejecta interacting with high-latitude material that extends from the ER toward the outer rings. Further observations of this emission will make it possible to determine the detailed geometry of the high-latitude material and provide insight into the formation of the rings and the mass-loss history of the progenitor.

Final Spitzer IRAC Observations of the Rise and Fall of SN 1987A

“…The decomposition also clearly shows that at 3.6 µm the west side of the ER is brightening relative to the rest of the ER. The behavior is consistent with that observed in the better spatially-resolved and better temporally-sampled X-ray and optical results obtained by Frank et al (2016) and Larsson et al (2019). Our first time interval, Days 7156 -8856, spans the time when both the optical and X-ray emission were transitioning from a brighter eastern side to a brighter western side.…”

“…Figure 2depicts the application of this model to the Spitzer data, Chandra X-ray data(Frank et al 2016), and Hubble optical data(Larsson et al 2019). The X-ray data are supplemented with 4 additional epochs of observations (from GO cycles 17 and 18) which were similarly acquired and reduced as described byFrank et al (2016).…”

Supernovae and transients with circumstellar interaction

“…Since then, an ongoing effort with HST (summarized in [ 181 ]) has revealed the circumstellar environment in exquisite detail. In particular, continuing observations over three decades since SN 1987A have shown how the inner equatorial ring has been illuminated by X-rays from late-time interaction with the ejecta ( figure 6 ), and helped constrain the mass loss history of the progenitor [ 182 ].

Figure 6.

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The morphology of the ejecta of SN 1987A at 31 years from 1150 to 10000 Å

“…Other data we use for comparison with ours throughout this paper are summarized in Table 2. The VLT/UVES spectra from 2017-10-19 are described in Larsson et al (2019b).…”

“…The ER may now be in the process of being destroyed by the interaction, but Orlando et al (2019) have predicted it to survive the interaction, at least until 40 years post-explosion where their simulation ends. The outer ejecta, advancing beyond the ER, are now interacting with the diffuse gas between the ER and the ORs (Larsson et al 2019b), creating new, fainter hotspots there. A reverse shock (RS) can also be observed, propagating inward in the frame of the ejecta, with a shape suggested to be bipolar with a narrower 'waist' inside the ER (Chevalier & Dwarkadas 1995;France et al 2015).…”