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Stellar Astrophysics

— the study of stars, from their birth to death.

Periods and classifications of RR Lyrae stars in the globular cluster M15
Stellar Astrophysics - Data Analysis
Hoffman, Murakami, Zheng, et al. 2020, in press. arxiv: 2008.09778

"We present measurements of the periods, amplitudes, and types of 78 RR Lyrae stars in the globular cluster M15 derived from Nickel 1 m telescope observations conducted at Lick Observatory in 2019 and 2020. Of these, two were previously reported but without a determination of the period. In addition, we identify five Cepheid variable stars for which we report three novel period determinations, and a further 35 stars with uncertain classifications and periods. We discuss the development and subsequent application to our data of a new Python package, Period-determination and Identification Pipeline Suite (PIPS), based on a new adaptive free-form fitting technique to detect the periods of variable stars with a clear treatment of uncertainties."

Modulation Over 40+ Years: Independent and Combined Observations of RR Lyrae Stars in M15
Stellar Astrophysics - Data Analysis
236th APS meeting (iPoster session 132.04).
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Modern sky-survey type observations are optimized for covering the large area of the sky. Although this provides a large amount of data for the study of variable stars, the cadence of observation is not high enough for short-period variables, such as RR Lyrae. For such data, traditional methods to determine periods, such as Lomb-Scargle Periodogram, do not provide the true value or a good estimation of the uncertainty. We have developed a new algorithm that addresses this issue. The initial study of this algorithm is included in M15 project and presented at 236th APS meeting.