Abstract Details
| Name: Koshvendra Singh Affiliation: Tata Institute of Fundamental Research Conference ID: ASI2024_34 Title : Hotspot Movement over stellar surface during an outburst in a Young Stellar Object: EX Lupi Authors and Co-Authors : Koshvendra Singh, Joe P. Ninan, Marina M. Romanova, David A. H. Buckley, Devendra K. Ojha, Arpan Ghosh, Andrew Monson, Malte Schramm, Saurabh Sharma, Daniel E. Reichart, Joanna Mikolajewska, Juan Carlos Beamin, J. Borissova, Valentin D. Ivanov, Vladimir V. Kouprianov, Franz-Josef Hambsch and Andrew Pearce Abstract Type : Oral Abstract Category : Stars, Interstellar Medium, and Astrochemistry in Milky Way Abstract : In this talk, I will present our first discovery of migration of the magnetic accretion funnel footprint during a period of enhanced accretion onto a young stellar object (YSO), EX Lupi. This phenomenon was predicted by dipolar magnetic field MHD simulations more than a decade ago. EX Lupi is the prototype of a class of young stellar objects (YSOs), EXors, that undergo repetitive outbursts (brightness increase by a few to a hundred) on the time scales of a few months to years. Though EX Lupi has a long history of recorded and well-studied outbursts since the 1940s, the most recent 2022’s outburst could be observed by us as well as other astronomers around the globe at an unprecedented cadence. We observed spectroscopically with HRS on 10-m SALT, SA and photometrically with LCRO, TMMT and CTIO. This data, along with the other publicly available data from ASAS-SN, TESS and AAVSO, enables accurate modelling of the accretion funnel footprint. I shall present how our analysis shows that the hotspot, the footprint of disk-mediated accretion onto the star, moved azimuthally ahead on the stellar surface by ∼ 112◦± 5◦, along the star’s rotation during the March 2022 outburst. The hotspot also moved down to a lower latitude by ∼ 10◦. Our 3-dimensional MHD simulations support the hotspot’s movement over the stellar surface during the state of high accretion rate. The hotspot held on to its new location even after the completion of the outburst, leading us to hypothesise a heated and thickened inner disk during the outburst. Our further analysis showed the pre-outburst azimuthally concentrated hotspot gains a temperature gradient during the outburst and gets azimuthally spread. These results also have broader implications on the other compact accreting sources. |