In some \delta 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 \log t = 9.1 .
Employing archival time series data from different sources , two frequencies f _ { 0 } = 10.034 c/d and f _ { 1 } = 12.681 c/d and their harmonics and linear combinations were identified .
The period ratio of f _ { 0 } / f _ { 1 } = 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 .