Five Years of Mid-Infrared Evolution of the Remnant of SN 1987A: The Encounter Between the Blast Wave and the Dusty Equatorial Ring

摘要: We have used the Spitzer satellite to monitor mid-IR evolution of SN 1987A over a five year period spanning epochs between days ~6000 and 8000 since explosion. The supernova (SN) has evolved into remnant its radiative output is dominated by interaction blast wave with pre-existing equatorial ring (ER). spectrum emission from ~180 K silicate dust, collisionally heated hot X-ray emitting gas temperature density ~5 × 106 K ~3 104 cm–3, respectively. mass radiating dust ~1.2 10–6 M ☉ on day 7554 scales linearly IR flux. Comparison data soft flux derived Chandra observations shows that IR-to-X-ray ratio, IRX, roughly constant value 2.5. Gas-grain collisions therefore dominate cooling shocked gas. constancy IRX most consistent scenario very little grain processing or occurred throughout this epoch. shape remained unchanged during while total increased factor time dependence t'0.87± 0.20, t' being first encounter ER. These are transitioning free expansion Sedov phase as it propagates main body ER, also suggested observations. spectral provides strong constraints in which takes place. Silicate grains, radii ~0.2 μm T ~ 180 K, best fit temporal ~8-30 data. spectra show presence secondary population small, (T 350 K), featureless dust. If these grains spatially coexist silicates, then they must shorter lifetimes. slightly different rates increase their respective fluxes, lending some support hypothesis. However, origin component exact nature relation still major unsolved puzzle.