Twenty-five Years of Visual and Near-Infrared Photometric Observations of the SRc Variable Star TV Geminorum
Volume 52 number 2 (2024)
- Richard Wasatonic
- 170 Hillside Drive, Coopersburg, PA 18036; rwasatonic@aol.com
Abstract
Visual band (λ555-nm) and near-IR (λ719-nm, λ754-nm, λ1024-nm) photoelectric observations of the M0-M1.5Iab+B4III SRc supergiant TV Geminorum are presented. The observations were conducted over a period of 25 years from 1997 to 2022. The aim of conducting the observations was to verify or refute basic variable star properties such as periodicities and amplitudes and physical parameters such as temperatures, luminosities, and radii by comparing the results against existing literature data. The V-band observations were made to continually monitor magnitude variations to ascertain periodicities and variable amplitudes. The 25-year de-reddened V-band average magnitude was 3.89 ± 4.47 × 10^–2, with an average amplitude of 3.51 × 10^–1 ± 3.37 × 10^–2 mag. Using the V-band observations and subsequent Fourier analysis, a short-term period of 459 ± 7 days was found along with a long secondary period (LSP) of 2525 ± 250 days. The near-IR observations were made to calculate estimates of changing effective temperatures, luminosities, and—with caution—radii. From the near-IR observations effective temperatures varied from a minimum of 3.54 × 10^3 K to a maximum of 3.82 × 10^3 K; the 25-year average temperature was 3.71 ×10^3 ± 1.10 × 10^1 K. Using an adopted distance of 2.15 kpc and after correcting for interstellar reddening, luminosities varied from 2.06 × 105 Lsun at minimum to 2.87 × 10^5 Lsun at maximum, with the 25-year average of 2.49 × 10^5 ± 2.86 × 10^3 Lsun. Temperature/luminosity non-correlations (maxima and minima values occurring at different times) occurred as a rule. Hence, only “snapshot” estimates of radii were calculated when temperature and luminosity were both at their respective maxima and/or minima. These exceptions yielded a TV Gem average radius of 1.21 × 10^3 Rsun. All of the photometric results were found to be compatible with current literature data.