The Second Black Hole Image of M87^*: Theoretical Insights from Multi-Year Observations by the Event Horizon Telescope

Hung-Yi Pu^1,2,3*, Keiichi Asada³, Britt Jeter³, Satoki Matsushita³, Geoff Bower³, Cristina Romero-Cañizales³, Cheng-Yu Kuo^4,3, Chih-Wei L. Huang³, Ming-Tan Chen³, Paul Ho³

¹Department of Physics, National Taiwan Normal University, Taipei, Taiwan
²Center of Gravitation and Astronomy, National Taiwan Normal University, Taipei, Taiwan
³Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
⁴Deparment of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan

* Presenter:Hung-Yi Pu, email:hypu@gapps.ntnu.edu.tw

In 2019, the Event Horizon Telescope Collaboration (EHTC) unveiled the first image of a black hole, based on observations of the supermassive black hole M87^* captured in 2017. Subsequent observations in 2018, during which the Greenland Telescope (GLT) join the EHT observations for the first time, revealed a persistent ring-like structure, consistent with the 2017 image. Despite the similarities between the two images, slight variations in the brightest parts of the ring were observed. How can we interpret these similarities and differences across years? Moreover, how can multi-year observations improve our understanding of the astrophysical properties of M87^*? In this talk, on behalf of EHTC, we will provide an overview of how the EHTC prepared a new image library, developed novel methods for comparing observational data with theoretical models, and gained insights into the nature of M87^* through multi-epoch data.

Keywords: Event Horizon Telescope (EHT), Greenland Telescope (GLT), Very long baseline interferometry (VLBI), black hole image, M87