| Name: Snigdha Sarmah |
| Affiliation: Tezpur University |
| Conference ID: ASI2026_695 |
| Title: Pre-explosion Variability and Circumstellar Environments of Type II Supernova Progenitors |
| Abstract Type: Poster |
| Abstract Category: Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Author(s) and Co-Author(s) with Affiliation: Snigdha Sarmah(Tezpur University, Tezpur - 784028, India), Rupak Roy(Institute of Astronomy Space and Earth Science, Kolkata - 700054, India), Rupjyoti Gogoi(Tezpur University, Tezpur - 784028, India), P. Shalima(Manipal Academy of Higher Education, Manipal - 576104, India) |
| Abstract: Red supergiants (RSGs) are widely accepted as the progenitors of hydrogen-rich Type II supernovae, yet their physical state in the final years before core collapse remains poorly constrained. In this work, we investigate the pre-explosion variability and circumstellar environments of eight nearby Type II supernova progenitors using multi-epoch, mid-infrared observations from the Spitzer Space Telescope, supplemented by high-resolution Hubble Space Telescope imaging and ultraviolet data from GALEX. To overcome severe source blending in the low-resolution Spitzer IRAC & GALEX images, we employ template-fitting photometry using HST priors, enabling reliable extraction of progenitor light curves in the 3.6 and 4.5 μm bands. All progenitors exhibit mid-infrared variability, with periods ranging from 179.8 ± 11.2 to 1231.3 ± 140.1 days, derived using Lomb-Scargle periodogram analysis. We place these progenitors on the established red supergiant period-luminosity relation and find that several sources display systematic offsets. In particular, enhanced 4.5 μm emission and redder [3.6] − [4.5] colours relative to Magellanic Cloud RSGs indicate the presence of circumstellar dust formed in the final decades prior to explosion. The mid-infrared colours show a tendency to redden with increasing pulsation period, consistent with episodic mass-loss events in advanced evolutionary stages. We further explore connections between progenitor properties and early supernova observables. For events with well constrained early-time parameters, it is seen that redder progenitors exhibit longer-lasting flash-ionization features, suggesting more extended or denser circumstellar material. |
