* Astronomy

Title: A Spitzer Space Telescope study of SN 2002hh: an infrared echo from a Type IIP supernova
Authors: W. P. S. Meikle (1), S. Mattila (2), C. L. Gerardy (1), R. Kotak (3), M. Pozzo (1), S. D. van Dyk (4), D. Farrah (5), R. A. Fesen (6), A. V. Filippenko (7), C. Fransson (8), P. Lundqvist (8), J. Sollerman (9), J. C. Wheeler (10) ((1) Imperial College London, (2) Queen's University Belfast, (3) European Southern Observatory, (4) IPAC, California Institute of Technology, (5) Cornell University, (6) Dartmouth College, (7) University of California, Berkeley, (8) Stockholm University (9) University of Copenhagen, (10) The University of Texas at Austin)

Researchers present late-time (590-994 d) mid-IR photometry of the normal, but highly-reddened Type IIP supernova SN 2002hh. Bright, cool, slowly-fading emission is detected from the direction of the supernova. Most of this flux appears not to be driven by the supernova event but instead probably originates in a cool, obscured star-formation region or molecular cloud along the line-of-sight. The researchers also show, however, that the declining component of the flux is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR emission could also be coming from newly-condensed dust and/or an ejecta/CSM impact but their contributions are likely to be small. For the case of a CSM-IR echo, they infer a dust mass of as little as 0.036 solar masses with a corresponding CSM mass of 3.6(0.01/r(dg))solar masses where r(dg) is the dust-to-gas mass ratio. Such a CSM would have resulted from episodic mass loss whose rate declined significantly about 28,000 years ago. Alternatively, an IR echo from a surrounding, dense, dusty molecular cloud might also have been responsible for the fading component. Either way, this is the first time that an IR echo has been clearly identified in a Type IIP supernova.
The researchers find no evidence for or against the proposal that Type IIP supernovae produce large amounts of dust via grain condensation in the ejecta. However, within the CSM-IR echo scenario, the mass of dust derived implies that the progenitors of the most common of core-collapse supernovae may make an important contribution to the universal dust content.

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