| タイトル | Five Years of Mid-Infrared Evolution of the Remnant of SN 1987A: The Encounter Between the Blast Wave and the Dusty Equatorial Ring |
| 本文（外部サイト） | http://hdl.handle.net/2060/20100025479 |
| 著者（英） | Gehrz, Robert D.; Challis, Peter; Bouchet, Patrice; Park, Sangwook; Dwek, Eli; Danziger, I. John; Woodward, Charles E.; Polomski, Elisha F.; Arendt, Richard G.; De Buizer, James M.; Burrows, David N.; Slavin, Jonathan D. |
| 著者所属（英） | NASA Goddard Space Flight Center |
| 発行日 | 2010-01-01 |
| 言語 | eng |
| 内容記述 | We have used the Spitzer satellite to monitor the laid-IR evolution of SN 1987A over a 5 year period spanning the epochs between days 6000 and 8000 since the explosion. The supernova (SN) has evolved into a supernova remnant (SNR) and its radiative output, is dominated by the interaction of the SN blast wave with the pre-existing equatorial ring (ER). The mid-IR spectrum is dominated by emission from approximately 180 K silicate dust, collisionally-heated by the hot X-ray emitting gas with a temperature and density of 5 x 10(exp 6) K and approximately 3 x 10(exp 4) per cubic centimeter, respectively. The mass of the radiating dust is approximately 1.2 x 10(exp -6) solar mass on day 7554, and scales linearly with IR flux. Comparison of the IR data with the soft X-ray flux derived from Chandra observations shows that the IR-to-X-ray flux ratio, IRX, is roughly constant with a value of 2.5. Gas-grain collisions therefore dominate the cooling of the shocked gas. The constancy of IRX is most consistent with the scenario that very little grain processing or gas cooling have occurred throughout this epoch. The shape of the dust spectrum remained unchanged during the observations while the total flux increased by a factor of approximately 5 with a time dependence of t(sup '0.87 plus or minus 0.20), t' being the time since the first encounter between the blast wave and the ER. These observations are consistent with the transitioning of the blast wave from free expansion to a Sedov phase as it propagates into the main body of the ER, as also suggested by X-ray observations. The constant spectral shape of they IR, emission provides strong constraints on the density and temperature of the shocked gas in which the interaction takes place. The IR spectra also suggest the presence of a secondary population of very small, hot (T greater than or equal to 350 K), featureless dust. If these grains spatially coexists with the silicates, then they must have shorter lifetimes. The data show slightly different rates of increase of their respective fluxes, lending some support to this hypothesis. However, the origin of this emission component and the exact nature of its relation to the silicate emission is still a major unsolved puzzle. |
| NASA分類 | Astrophysics |
| 権利 | Copyright, Distribution as joint owner in the copyright |
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