Infrared Continuum and Line Evolution of the Equatorial Ring Around Sn 1987a

Abstract

Spitzer observations of SN 1987A have now spanned more than a decade. Since day ∼4000, mid-infrared (mid-IR) emission has been dominated by that from shock-heated dust in the equatorial ring (ER). From 6000 to 8000 days after the explosion, Spitzer observations included broadband photometry at 3.6-24 μm, and low and moderate resolution spectroscopy at 5-35 μm. Here we present later Spitzer observations, through day 10,377, which include only the broadband measurements at 3.6 and 4.5 μm. These data show that the 3.6 and 4.5 μm brightness has clearly begun to fade after day ∼8500, and no longer tracks the X-ray emission as well as it did at earlier epochs. This can be explained by the destruction of the dust in the ER on timescales shorter than the cooling time for the shocked gas. We find that the evolution of the late time IR emission is also similar to the now fading optical emission. We provide the complete record of the IR emission lines, as seen by Spitzer prior to day 8000. The past evolution of the gas as seen by the IR emission lines seems largely consistent with the optical emission, although the IR [Fe II] and [Si II] lines show different, peculiar velocity structures.

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

“…A change in the evolution of the ER has also been observed at other wavelengths. The mid-IR emission, which is due to shock-heated dust, peaked around 8500 days and shows a similar evolution as the optical light curves (Arendt et al 2016). The shocks in the hotspots also produce soft X-ray emission, which can be described by a ∼ 0.3 keV collisional ionization equilibrium plasma (Frank et al 2016).…”

“…This evolution has been accompanied by the appearance of faint spots outside the ER in the HST images after 9500 days. Observations at other wavelengths have also revealed transitions in the evolution of the ER, including fading in the IR (Arendt et al 2016), a flattening of soft X-rays (Frank et al 2016) and a reacceleration of the blast wave in radio (Cendes et al 2018). All these observations show that the remnant of SN 1987A has entered a new phase.…”

Dust in Supernovae and Supernova Remnants II: Processing and Survival

“…5;Jakobsen et al 1991. These rings are thought to be composed of the material lost from the progenitor, when Evolution of the infrared and X-ray fluxes of SN 1987A (Arendt et al 2016). Both the infrared and X-ray fluxes have continuously increased until 2012.…”

“…In contrast to the infrared brightness, the X-ray luminosity continued to increase. Arendt et al (2016) suggest that the time scale for the destruction of dust grains is shorter than the cooling time of the shocked gas: the bulk mass of dust has been reduced by shock destruction, decreasing the infrared brightness, while the X-ray flux reflects the temperature (but also the density and volume) of the shocked gas.…”

Dust in Supernovae and Supernova Remnants II: Processing and Survival

“…These rings are thought to be composed of the material lost from the progenitor, when Fig. 6 Evolution of the infrared and X-ray fluxes of SN 1987A (Arendt et al 2016). Both the infrared and X-ray fluxes have continuously increased until 2012.…”