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arXiv · 2303.04421

Monitoring the Size and Flux Density of Sgr A* during the Active State in 2019 with East Asian VLBI Network

Xiaopeng Cheng·Ilje Cho·Tomohisa Kawashima·Motoki Kino·Guang-Yao Zhao·Juan-Carlos Algaba·Yutaro Kofuji·Sang-Sung Lee·Jee-Won Lee·Whee Yeon Cheong·Wu Jiang·Junghwan Oh
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Abstract

In this work, we studied the Galactic Center supermassive black hole (SMBH), Sagittarius A* (Sgr A*), with the KVN and VERA Array (KaVA)/East Asian VLBI Network (EAVN) monitoring observations. Especially on 13 May 2019, Sgr A* experienced an unprecedented bright near infra-red (NIR) flare; so, we find a possible counterpart at 43 GHz (7 mm). As a result, a large temporal variation of the flux density at the level 15.4%, with the highest flux density of 2.04 Jy, is found on 11 May 2019. Interestingly, the intrinsic sizes are also variable, and the area and major-axis size show a marginal correlation with flux density with >2{\sigma}. Thus, we interpret that the emission region at 43 GHz follows the larger-when-brighter relation in 2019. The possible origins are discussed with an emergence of a weak jet/outflow component and the position angle change of the rotation axis of the accretion disk in time.

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Xiaopeng Cheng, Ilje Cho, Tomohisa Kawashima, Motoki Kino, Guang-Yao Zhao, Juan-Carlos Algaba, Yutaro Kofuji, Sang-Sung Lee, Jee-Won Lee, Whee Yeon Cheong, Wu Jiang, Junghwan Oh. 2023-03-08. Monitoring the Size and Flux Density of Sgr A* during the Active State in 2019 with East Asian VLBI Network. https://doi.org/10.3390/galaxies11020046

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