Effective temperature and radial velocity of the small-amplitude Cepheid Polaris (alpha UMi) in 2015
I. A. Usenko, V. V. Kovtyukh, A. S. Miroshnichenko, and S. Danford
TL;DR
This study analyzes Polaris in 2015, revealing increased pulsation period and radial velocity amplitude, with temperature near the red edge of the Cepheid instability strip, indicating evolutionary changes.
Contribution
It provides new observational data on Polaris's pulsation period, velocity amplitude, and temperature, highlighting its movement toward the red edge of the Cepheid instability strip.
Findings
Pulsation period increased to 8.6 minutes since 2007
Radial velocity amplitude approximately doubled since 2007
Effective temperature remained close to 2001-2004 values
Abstract
We present the results of an analysis of 21 spectra of alpha UMi (Polaris) obtained in September - December 2015. Frequency analysis shows an increase of the pulsation period up to 8.6 min in comparison to the 2007 observational set. The radial velocity amplitude comes to 4.16 km s^-1, and it approximately twice the one found in 2007. The average Teff = 6017 K, and it is close to the value determined for the 2001-2004 set. Therefore Polaris moves to the red edge of the Cepheid instability strip (CIS)
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