SEMINÁRIO DO DEPARTAMENTO DE ASTRONOMIA
Solar and stellar white light flares: observational and modeling challenges
a talk by Paulo Simões (Universidade Presbiteriana Mackenzie/Brazil) - In-Person
Abstract:
The study of stellar flares has increased with new observations from CoRoT, Kepler, and TESS satellites, revealing the visible broadband emission from these events. Stellar flares have been modelled as a 10^4 K blackbody (BB) emission to obtain estimates of their total energy. Solar white light flares (WLFs) are much fainter than their stellar counterparts and can only be detected via spatially resolved observations. Since the 1st observation of a WLF in 1859 by Carrington and Hodgson, the origin of the visible continuum remains a challenge in flare physics. Identifying this radiation mechanism is crucial to understand the energy transfer during these events. But spectral data for WLFs are relatively rare, and insufficient to remove the ambiguity of their origin: photospheric BB radiation or Paschen continuum from hydrogen recombination in the chromosphere. We discuss the challenges in observations and modelling of solar and stellar WLFs, in terms of the physical processes and energy deposition in the flaring atmosphere and past observations. We also present our recent results where we compared the energy estimates of stellar flares using the BB and H recombination models. Analyzing 42 events from Kepler-411 and Kepler-396, we find that estimates for the total flare energy from the H recombination spectrum are about an order of magnitude lower than the values obtained from the BB radiation. Given the known energy transfer processes in flares, we argue that the former is a physically more plausible model than the latter to explain the origin of WLFs. Lastly, we introduce a new Solar UV-NIR Spectrometer (SUNS) for solar observations at Mackenzie. It will provide new resolved spectra of WLFs in the visible range, that will allow us to put the current models to the test and step towards a solution to the 165-year-old mystery of the origin of WLFs.
Short-Bio:
Paulo Simões is a solar physicist with 20+ years of experience in solar flare studies using multi-wavelength data, from radio waves to gamma rays, and simulations. He is a professor at Mackenzie Presbyterian University (MPU, Brazil) and researcher at the Center for Radio Astronomy & Astrophysics Mackenzie (CRAAM). Obtained his MSc in Astrophysics in 2005 and PhD in Space Geophysics in 2009 at the National Institute for Space Research (INPE).
Google Meet: https://meet.google.com/pcw-gmem-jyi
Link da transmissão: https://www.youtube.com/c/AstronomiaIAGUSP/live