Astronomy and Astrophysics – Astronomy
Scientific paper
May 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007sptz.prop40968g&link_type=abstract
Spitzer Proposal ID #40968
Astronomy and Astrophysics
Astronomy
Scientific paper
We are carrying out an intensive study of the physical and evolutionary properties of Classical Cepheids, known as the 'Secret Lives of Cepheids' (SLiC) program. This program covers a wide range of periods and pulsation amplitudes, and makes use of X-ray/UV/optical observations. The major science goals of our proposed Spitzer program are to investigate two recently discovered characteristics of Classical Cepheids, hitherto unknown. These are the presence of circumstellar envelopes (CSEs) around three nearby Cepheids (Polaris, delta Cep and L Car - all SLiC program stars), and the existence of O VI (1032/36A) and C III (977A) emission lines in the far-UV spectra of two program stars - Polaris and beta Dor. These lines form in the chromospheres/transition regions of the Cepheids and, in the case of beta Dor, show variations that correlate to the pulsations of the star. We propose SST/IRS high-resolution spectroscopy of these four nearby, bright Classical Cepheids, three of which have been found, from long-baseline near-IR interferometry, to have CSEs ~0.5-3.0 AU from the central star. From the proposed IRS spectra, we will determine the physical characteristics of the circumstellar material/envelopes, likely arising from mass loss or, given the young ages of Cepheids, debris disks. Also, we will use the IRS spectra to explore the presence of emission lines related to those discovered in the far-UV. Possible low density He I and H I wind lines will also be measured, if present. As in the case of the FUSE far-UV observations, SST/IRS also provides the opportunity to observe and measure these emission lines at wavelengths where the Cepheid photospheric continua are very low. In the near-UV to near-IR regions, emission lines are overwhelmed by the photospheric continua. With the modest amount of time requested (~1.86-hours), the proposed IRS observations will be crucial in understanding these newly discovered characteristics of Astronomy's most important and 'best-known' class of variable stars.
Engle Scott
Evans Nancy
Guinan Edward
Harper Graham
Marenago Massimo
No associations
LandOfFree
The Secret IR Lives of Cepheids: Spitzer IRS Spectroscopy of Circumstellar Envelopes, Winds and Chromospheric Emissions in Nearby Cepheids 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 The Secret IR Lives of Cepheids: Spitzer IRS Spectroscopy of Circumstellar Envelopes, Winds and Chromospheric Emissions in Nearby Cepheids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Secret IR Lives of Cepheids: Spitzer IRS Spectroscopy of Circumstellar Envelopes, Winds and Chromospheric Emissions in Nearby Cepheids will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1750550