Title: Detection of a Far-Infrared Bow-Shock Nebula Around R Hya: the First MIRIAD Results
Authors: T. Ueta (NASA Ames/SOFIA), A. K. Speck (U. of Missouri), R. E. Stencel (U. of Denver), F. Herwig (LANL), R. D. Gehrz (U. of Minnesota), R. Szczerba (CAMK, Poland), H. Izumiura (OAO/NAO, Japan), A. A. Zijlstra (U. of Manchester, UK), W. B. Latter (NHSC/Caltech), M. Matsuura (NAO, Japan), M. Meixner (STScI), M. Steffen (AIP, Germany), M. Elitzur (U. of Kentucky)

Researchers present the first results of the MIRIAD (MIPS (Multiband Imaging Photometer for Spitzer) Infra-Red Imaging of AGB (asymptotic giant branch)Dustshells) project using the Spitzer Space Telescope. The primary aim of the project is to probe the material distribution in the extended circumstellar envelopes (CSE) of evolved stars and recover the fossil record of their mass loss history. Hence, they must map the whole of the CSEs plus the surrounding sky for background subtraction, while avoiding the central star that is brighter than the detector saturation limit. With their unique mapping strategy, the researchers have achieved better than one MJy/sr sensitivity in three hours of integration and successfully detected a faint (< 5 MJy/sr), extended (~400 arcsec) far-infrared nebula around the AGB star R Hydrae.
Based on the parabolic structure of the nebula, the direction of the space motion of the star with respect to the nebula shape, and the presence of extended H alpha emission co-spatial to the nebula, they suggest that the detected far-IR nebula is due to a bow shock at the interface of the interstellar medium and the AGB wind of this moving star. This is the first detection of the stellar-wind bow-shock interaction for an AGB star and exemplifies the potential of Spitzer as a tool to examine the detailed structure of extended far-IR nebulae around bright central sources.

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Extra information
The variability of R Hydrae was discovered in 1704. Until 1770, the period was nearly constant at 495 days. From 1770 to 1950 the period decreased to 395 days and has remained constant since that date. R Hya can be as bright as + 3.7 and as faint as + 10.3. On average the brightness lies between +4.5 and +9.5.
Although this star has a southern declination, it is also very easy to observe from a big part of the northern hemisphere. At maximum it is a naked eye or a binocular object, at minimum only a small telescope is needed R Hydrae is very easy to find starting from gamma Hydrae.

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