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تسجيل مستخدم جديدSN 1987A After 18 Years: Mid-Infrared GEMINI and SPITZER Observations of the Remnant
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We present high resolution 11.7 and 18.3um mid-IR images of SN 1987A obtained on day 6526 with T-ReCS attached to the Gemini telescope. The 11.7um flux has increased significantly since our last observations on day 6067. The images clearly show that all the emission arises from the equatorial ring (ER). Spectra obtained with Spitzer, on day 6184 with MIPS at 24um, on day 6130 with IRAC in the 3.6-8um region, and on day 6190 with IRS in the 12-37um region show that the emission consists of thermal emission from silicate dust that condensed out in the red giant wind of the progenitor star. The dust temperature is ~166K, and the emitting dust mass is ~2.6 x 10-6 Msun. Lines of [Ne II]12.82um and [Ne III]15.56um are clearly present, as well as a weak [Si II]34.8um line. We also detect two lines near 26um which we tentatively ascribe to [Fe II]25.99um and [O IV]25.91um. Comparison of the Gemini 11.7um image with X-ray images from Chandra, UV-optical images from HST, and radio synchrotron images obtained by the ATCA show generally good correlation of the images across all wavelengths. Because of the limited resolution of the mid-IR images we cannot uniquely determine the location or heating mechanism of the dust giving rise to the emission. The dust could be collisionally heated by the X-ray emitting plasma, providing a unique diagnostic of plasma conditions. Alternatively, the dust could be radiatively heated in the dense UV-optical knots that are overrun by the advancing supernova blast wave. In either case the dust-to-gas mass ratio in the circumstellar medium around the supernova is significantly lower than that in the general ISM of the LMC, suggesting either a low condensation efficiency in the wind of the progenitor star, or the efficient destruction of the dust by the SN blast wave.
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We have used the Spitzer satellite to monitor the mid-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 ou
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g, not the ejecta, and is brightest on the west side. Decomposition of the marginally resolved emission also confirms this, and shows that the west side of the ER has been brightening relative to the other portions of the ER. The infrared (IR) morphological changes resemble those seen in both the soft X-ray emission and the optical emission. The integrated ER light curves at 3.6 and 4.5 $mu$m are more similar to the optical light curves than the soft X-ray light curve, though differences would be expected if dust is responsible for this emission and its destruction is rapid. Future observations with the James Webb Space Telescope will continue to monitor the ER evolution, and will reveal the true spectrum and nature of the material responsible for the broadband emission at 3.6 and 4.5 $mu$m. The present observations also serendipitously reveal a nearby variable source, subsequently identified as a Be star, that has gone through a multi-year outburst during the course of these observations.
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