Physics
Scientific paper
Jul 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008hst..prop11726g&link_type=abstract
HST Proposal ID #11726. Cycle 17
Physics
Scientific paper
The major aims of this proposal are twofold: to confirm and understand the recently observed apparent evolutionary changes of the bright {3.97-day} Cepheid Polaris ? and ? to further study the recent discovery of hot plasmas {up to 1MK} well above the photospheric temperature of the Cepheid itself. This study will have a major impact on understanding the evolution, structure, heating and dynamics of Cepheid {and related Hybrid Star} atmospheres. In our study ? the Secret Lives of Cepheids ? Polaris is noteworthy for its well-documented increase in pulsation period {+3.51 sec/year} and decrease in light amplitude over the last 100-150 years, almost ceasing pulsations in the early 1990s. Moreover, our studies of photoelectric photometry and historic visual observations have shown evidence that Polaris may have increased in brightness by almost 0.2-mag over the past century {and possibly by more than 1-mag since Ptolemy}. In addition, a study of the IUE database indicates a possible increase in photospheric temperature {which the FUV region is very sensitive to} between 1978/79 and 1991/93, pointing to a change of 35+/-12 K. More recently, FUSE and Chandra observations of Polaris indicate the presence of C III 977/1176A and O VI 1032/1038A emissions, as well as possible soft X-ray emission, respectively. The source of these hot plasmas could be related to pulsations {shock heating} and/or magnetic activity. To further investigate the evolutionary changes and upper atmospheric emissions of Polaris, we propose for HST/COS medium resolution spectrometry covering the wavelength range 1150?2100A. This wavelength range covers both the high energy emission lines {<1600A} along with the rise in continuum of the F-supergiant photosphere {>1600A}. HST/COS is the only instrument capable of carrying out the necessary FUV observations to achieve our scientific goals for Polaris ? providing a better understanding of the evolution and heating mechanisms of Cepheids.;
No associations
LandOfFree
Mysteries of the North Star: HST/COS confirmation of real-time evolution and upper atmospheric heating in Polaris does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Mysteries of the North Star: HST/COS confirmation of real-time evolution and upper atmospheric heating in Polaris, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mysteries of the North Star: HST/COS confirmation of real-time evolution and upper atmospheric heating in Polaris will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1320515