The Secret Lives of Cepheids: Tracking Pulsation-Induced UV and X-ray Variations in Classical Cepheids with HST, Chandra and XMM
Abstract
Classical Cepheids have been well-studied in terms of their cosmologically important Leavitt Law. However, they are also proving to be increasingly complex and astrophysically intriguing in terms of atmospheric energetics. The Secret Lives of Cepheids program has expanded our X-ray-UV (XUV) inventory with recently collected data to further probe Cepheid atmospheres and help understand their heating mechanisms. HST-COS FUV spectra revealed a wealth of 10,000-300,000K plasma emission lines, phase-locked with each Cepheid's pulsation periods, showing that a pulsation-driven heating mechanism is at work, even in the nearest and brightest Cepheid, Polaris. Observations of the ultra-low amplitude Polaris offer insights into the effects that even minimal pulsations have on a cool supergiant atmosphere, especially when compared to full amplitude Cepheids and also non-pulsating supergiants in the instability strip. Further X-UV data have also been gathered for delta Cep and beta Dor to better understand the full dynamics of their atmospheres. The latest results for these three Cepheids will be presented.
- Publication:
-
American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23510609E