Speaker
Description
The supernova remnant Cassiopeia A plays a unique role in radio astronomy and astrophysics and is currently being explored in various ways. We present recent developments in NenuFAR observations applied to Cas A at low frequencies. Beginning in 2019, the GURT one-baseline interferometer established the continuous radio spectrum of Cas A at 16–74 MHz, using Cyg A as a calibration source. Based on spectral results, data analysis provided an opportunity to estimate the absorption parameters of ionized gas both inside and outside the supernova remnant.
Subsequent studies continued in 2023, based on simultaneous observations conducted with the help of two different radio telescopes, URAN-2 and NenuFAR. The instruments were configured as one-baseline interferometers, and their spectral measurements were combined from two segments, covering the frequency range of 8–66 MHz. This is particularly significant because the spectral maximum of low-frequency radiation is located at approximately 21 MHz.
Considering long-term observations of Cas A's radio emission, including the most recent ones, we have noticed that the spectral peak frequency has changed over time. This effect is driven by the interaction between the supernova remnant and its surrounding interstellar medium.
Next, we utilized the more extensive capabilities of the NenuFAR radio telescope in multi-baseline interferometric mode. Observations were carried out from May to September 2024 during a period of high solar activity, and their records were subject to intensive scintillation. These observations have enabled investigations into both the integral continuous spectrum of Cas A and the power spectrum distribution of scintillation, caused by irregularities in the ionosphere and possibly in the interplanetary medium. The recent results complement previous research very well.
We thank the National Research Foundation of Ukraine for its financial and organizational support under the call “Excellent Science in Ukraine” (2024–2026), Grant No. 2023.03/0007.
