| Name: | Koshvendra Singh |
| Affiliation: | Tata Institute of Fundamental Research |
| Conference ID: | ASI2025_290 |
| Title: | Modelling the Accretion Hotspot of Low-Mass Young Stars: Insights into Thermal and Spatial Structure |
| Authors: | Koshvendra Singh, Joe P. Ninan, Devendra K. Ojha |
| Authors Affiliation: | Koshvendra Singh, Joe P. Ninan, Devendra K. Ojha (Tata Institute of Fundamental Research) |
| Mode of Presentation: | Poster |
| Abstract Category: | Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Abstract: | Low-mass young stars undergo magnetospheric accretion where disk matter follows stellar magnetic field lines and freely falls on the star creating a shock-heated region with ∼104K temperature, called hotspot. The hotspot can be regarded as a 2-dimensional (2D) slice at the stellar surface of a 3D accretion dynamics across the disk and star. It carries imprints of the variable accretion dynamics (Espaillat et al. 2021, Singh et al. 2024 ). The hotspot is very responsible for the thermal-chemical-mineralogical evolution of the irradiated disk. However, the thermal and spatial structure of the hotspot is not well understood. In this talk, I will present our recent work on modeling the thermal-spatial structure of the hotspot. We modeled the thermal profile along the two spherical coordinates by ‘Gaussian-like’ symmetric functions, motivated by the results of sophisticated 3D MHD simulations of magnetospheric accretions from Kulkarni and Romanova 2013. These profiles are further motivated by the analytical equation of the spatial distribution of accreting matter based on the star-disk geometry. The model observables are time-lag among lightcurves, indicating the temperature distribution in hotspots, peak-to-peak lightcurve amplitude, reflecting temperature ranges in it, as well as mass-accretion rate. We fit our model onto the observations of the dynamically and morphologically evolving hotspot of a young star named EX Lupi, during its outburst in March 2022. The thermal structure of the hotspot provides the extent of the stellar surface covered by density contours, providing insights into which parts of the disk are more efficiently cou- pled to the accretion. As the hotspot evolves over accretion variation as shown by Singh et al 2024, this model will provide insights into why specific regions of the disk are more prone to accretion than others leading to a better understanding of the accretion-outflow relation and its effect on the star-disk system. |
