TYC 3637-1152-1 – A high amplitude δ Scuti star with peculiar pulsational properties

Abstract

In some δ Scuti stars, only one or two radial modes are excited (usually the fundamental mode and/or first overtone mode) and the observed peak-to-peak amplitudes exceed 0.3 mag (V). These stars are known as High Amplitude Delta Scuti (HADS) variables.We here present a detailed photometric and spectroscopic analysis of the HADS star TYC 3637-1152-1. We have derived a metallicity close to solar, a spectral type of F4 V and an age of logt=9.1. Employing archival time series data from different sources, two frequencies f0 = 10.034 c/d and f1 = 12.681 c/d and their harmonics and linear combinations were identified. The period ratio of f0/f1=0.791 puts this star into a peculiar position in the Petersen diagram, from which we conclude that TYC 3637-1152-1 is a unique object with peculiar pulsational properties that indicate a transitional state between HADS stars pulsating in the fundamental and first overtone modes and stars pulsating in higher overtones.