Other
Scientific paper
Dec 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aas...19712901e&link_type=abstract
American Astronomical Society, 197th AAS Meeting, #129.01; Bulletin of the American Astronomical Society, Vol. 33, p.712
Other
Scientific paper
Amplitude: Polaris has presented us with the rare phenomenon of a Cepheid with a pulsation amplitude which has decreased over the last 50 years. In this study we investigate whether the amplitude decrease during the last 15 years has had any effect on upper atmosphere heating. We obtained IUE high and low resolution spectra but found no change in either the Mg II chromospheric emission or the flux at 1800 Å/ between 1978 and 1993 when the pulsation amplitude dropped by 50 % (from 2.8 to 1.6 km sec-1). The energy distribution from 1700 Å/ through V, B, R(KC), and I(KC) is like that of a nonvariable supergiant of the same color rather than a full amplitude Cepheid in that it has nonradiative flux at 1800 Å/ which the full amplitude Cepheid δ Cep lacks. Period Change: Polaris also has a rapidly changing period (3.2 sec/year), in common with other overtone pulsators. We argue that this is a natural consequence of the different envelope locations which dominate in growth rates in fundamental and overtone pulsation. In fundamental mode pulsators, the deeper envelope is more important in determining growth rates than for overtone pulsators. For fundamental mode pulsators, evolutionary changes in the radius produce approximately linear changes in period. In overtone pulsators, pulsation reacts to small evolutionary changes in a more unstable way because the modes are more sensitive to high envelope features such as opacity bumps, and the growth rates for the many closely spaced overtone modes change easily. Companions: The upper limit to the X-ray flux from an Einstein observation implies that the companion in the astrometric orbit is probably earlier than F4 V. The combination of upper and lower limits on the companion from IUE and Einstein respectively catch the companion mass between 1.7 and 1.4 M&sun; . The X-ray limit is consistent with the more distant companion α UMi B being a physical companion in a hierarchal triple system. However the X-ray limits imply that the even more distant companions α UMi C and D are probably too old to be physically associated with Polaris.
Remage Evans Nancy
Sasselov Dimitar D.
Short Christopher Ian
No associations
LandOfFree
Polaris: Amplitude, Period Change, and Companions 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 Polaris: Amplitude, Period Change, and Companions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polaris: Amplitude, Period Change, and Companions will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1729101