| Name: | Gautam Das |
| Affiliation: | Indian Institute of Science Education and Research Kolkata |
| Conference ID : | ASI2024_935 |
| Title : | Modelling of high resolution FUOrs spectrum to infer fundamental parameters of YSO accretion. |
| Authors : | Gautam Das, Archis Mukhopadhyay, Joe Phillip Ninan |
| Authors Affiliation: | 1 Gautam Das, Archis Mukhopadhyay Affiliation (Indian Institute of Science Education and Research Kolkata, Nadia - 741 246, India)
2 Joe Phillip Ninan Affiliation (Tata Institute of Fundamental Research Mumbai, Colaba - 400 005, India) |
| Mode of Presentation: | Poster |
| Abstract Category : | Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Abstract : | FU Ori-type outbursts are marked by a rapid increase in luminosity where flux due to the disk outshines that of the star. Previous works have shown that during this event, the accretion of matter from the disk onto the star increases by orders of magnitude than at the quiescent stage. Due to the rapid gas influx, the disk gets heated viscously. Some matter follows the stellar magnetic fields and falls onto the stellar surface at freefall velocities, creating shock regions of strong magnetic fields. In this work, we present a generative model for underlying accretion disk dynamics. Our tool can generate theoretical spectra of Young Stellar Objects (YSOs) from the basic PMS parameters.
We divided the star-disk system into four components, namely, viscous disk, magnetospheric accretion, dusty disk and stellar photosphere. The most dynamically exciting part is the viscous disk, modelled as the standard alpha disk. Due to fast rotations of the disk, radiation from sections of the disk gets Doppler shifted, which is seen as broadened dips. We developed a very computationally efficient process of continuous-convolution using a rotationally broadening kernel. This is several times faster than similar discrete-convolution processes proposed. In magnetospheric accretion shock regions, as gas (mainly Hydrogen) is heated up, we see Balmar jumps in spectroscopic observations. We have been able to recreate this using a hydrogen-slab model. The magnetospheric component has a significant contribution in low accreting cases. At higher accretions, no jumps are observed, suggesting that the magnetosphere is potentially crushed onto the stellar surface. Modelling the stellar photosphere using BT-Settl model, the radiation from the photosphere and viscous disk irradiates the dusty disk, producing a dusty disk spectrum. The overall spectrum obtained by combining all these flux components along with associated disk integration weight factors has been agreeing with similar models proposed.
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