| Authors : | Mami Deka, Department of Physics, Cotton University, Panbazar, Guwahati 781001, Assam, India
Shashi M. Kanbur, Departmet of Physics, State University of New York Oswego, Oswego, NY 13126, USA
Sukanta Deb, Department of Physics, Cotton University, Panbazar, Guwahati 781001, Assam, India |
| Abstract : | δ Scuti stars are intermediate-mass pulsating variable stars with masse range 1.0–3.0 solar mass having spectral types between A2 and F2 located at the intersection of the Cepheid instability strip with the main sequence. We can use them as astrophysical laboratories to test the theories of stellar evolution and pulsation. The single-mode δ Scuti stars obey a period–luminosity (PL) relation, which make them reliable distance estimators (McNamara 1997 , 2011 ;Ziaali et al. 2019 ; Poro et al. 2021 ; Barac et al. 2022 ) to our Galaxy as well as to nearby galaxies, while the multimode δ Scuti stars provide an important astrophysical tool to understand the properties of deep stellar interiors (Breger & Pamyatnykh 1998 ). In this work, we have investigated the observed Period-Colour-Amplitude-Colour (PCAC) relations at maximum/mean/minimum light of Galactic bulge and LMC δ Scuti stars for the first time and tested the theory of the interaction of hydrogen ionization front (HIF) and stellar photosphere of Simon et al. ( 1993 ) using MESA - RSP code. The PCAC relations as a function of pulsation phase are crucial probes of the structure of the outer envelope and offer an insight into the physics of stellar evolution and pulsation. The behaviour of the δ Scuti PCAC relations found in this study can be explained using the HIF-stellar photosphere interaction theory. Another important result, we found from this study is that the bulge δ Scutis are comparatively hotter than the LMC δ Scutis. |
