Photometric and Spectroscopic Review of the Beat Cepheid AS Cassiopeiae

Volume 52 number 1 (2024)

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Enrique T. Boeneker

Jilgueros 11, Las Aguilas, Mexico City, Ciudad de Mexico 01710, Mexico; heiner.boeneker@hotmail.com

Robin Leadbeater

Three Hills Observatory, The Birches, Wigton, Cumbria CA7 1JF, United Kingdom; robin@threehillsobservatory.co.uk

Abstract

Photometric and spectroscopic data of the galactic beat Cepheid star (DCEPB) AS Cas (ASASSN-V J002537.77+641347.9) were obtained from three AAVSOnet observatories of the American Association of Variable Star Observers (AAVSO) located in New Hampshire (BSM-NH2), New Mexico (BSM-NM2), and Hawaii (BSM-Hamren). The spectroscopic data and their analysis were performed at the Three Hills Observatory in Wigton, UK. A total of 9027 observations for light curve analysis were made with B, V, R, I Johnson-Cousins filters from July 22, 2020 to November 8, 2023. The photometric data were analyzed with the Date Compensated Discrete Fourier Transform (DCDFT) and CLEANest methods, yielding a fundamental period (P0) of 3.02465 days ± 0.00034 and a first-overtone period (P1) of 2.15547 days ± 0.00033. The epoch used for the curve analysis was JD 2459654.736. This set of new observations is the largest compared to those previously made. Our results confirm the double- mode nature of AS Cas and, therefore, its classification as a DCEPB star. A series of low-resolution spectra were recorded over a range of phases, allowing the change in spectral class to be tracked (G0I–F6I corresponding to a Teff range of 5590–6420 K). An interstellar reddening E (B–V) of 0.9 mag has been estimated from the shape of the spectrum continuum.