|HIFISTARS: The physical and chemical properties of circumstellar environments around evolved stars
|We propose to carry out a comprehensive study of circumstellar envelopes (CSEs) around evolved stars, as a HIFI GTKP. The main scientific aims are to gain deeper insight into the structure, thermodynamics, kinematics and chemistry of CSEs and into the mass-loss history of evolved stars, thereby advancing our understanding on the final stages of stellar evolution of the majority of stars and their resultant impact on the interstellar medium and the cosmic cycle. We will use the unique capabilities of HIFI to probe the inner regions of CSEs, by means of spectrally-resolved observations of the principal cooling transitions: thermal transitions of H2O, and high-excitation rotational transitions of CO and HCN. Such observations provide unique information about the shells where the gas temperatures are 100 - 2000 K and the material is being accelerated. We propose to observe a set of 38 objects, chosen to sample the parameter space of r^ance for evolved stars and their circumstellar material. For every star, 3 lines of both 12CO and 13CO will be observed to unravel the mass-loss history. To further unveil the inner structure in the CSEs, observations of different H2O lines are crucial, since H2O is a key molecule to understand the chemistry, the thermodynamics and the dynamics of the inner CSE. We propose to observe a carefully-selected list of H2O transitions covering different excitation degrees, including para- and ortho-H2O lines and a few isotopic lines. The high spectral resolution observations will allow us to determine the velocity field in the warm acceleration regions. With HCN being a major coolant in C-rich CSEs, 2 high-excitation lines will be observed in C-rich AGBs to probe the temperature structure. To further study the oxygen chemistry, we will obtain OH and [OI] lines from PACS GT data. Finally, we will address the puzzling question of the origin of water vapor observed previously in the extreme carbo...n star IRC+10216, and survey 9 additional C-rich stars for evidence of water.
|Herschel-HIFI observations of molecular emission in protoplanetary nebulae and young planetary nebulae . Bujarrabal V. et al. . Astronomy & Astrophysics, Volume 537, id.A8, 25 pp. . 537 . 10.1051/0004-6361/201117646 . 2012A&A...537A...8B ,
|Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
|Publisher And Registrant
|European Space Agency
|European Space Agency, 2012, KPGT_vbujarra_1, SPG v14.2.0. https://doi.org/10.5270/esa-4kubwqq