Monitoring the Size and Flux Density of Sgr A* during the Active State in 2019 with East Asian VLBI Network
Author:
Cheng Xiaopeng1ORCID, Cho Ilje2ORCID, Kawashima Tomohisa3ORCID, Kino Motoki45ORCID, Zhao Guang-Yao2ORCID, Algaba Juan-Carlos6ORCID, Kofuji Yutaro7, Lee Sang-Sung18ORCID, Lee Jee-Won1ORCID, Cheong Whee Yeon18ORCID, Jiang Wu9ORCID, Oh Junghwan10ORCID
Affiliation:
1. Korea Astronomy and Space Science Institute, Daedeok-daero 776, Yuseong-gu, Daejeon 34055, Republic of Korea 2. Instituto de Astrofísica de Andalucía—CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain 3. Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8582, Chiba, Japan 4. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka 181-8588, Tokyo, Japan 5. Academic Support Center, Kogakuin University of Technology & Engineering, 2665-1 Nakano, Hachioji 192-0015, Tokyo, Japan 6. Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia 7. Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu 023-0861, Iwate, Japan 8. University of Science and Technology, Gajeong-ro 217, Yuseong-gu, Daejeon 34113, Republic of Korea 9. Shanghai Astronomical Observatory, Chinese Academy of Sciences, Nandan Road 80, Shanghai 200030, China 10. Joint Institute for VLBI ERIC, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
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 in 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 marginal correlation with flux density with ≳2 σ. 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.
Funder
Spanish Ministerio de Economía y Competitividad Consejería de Economía, Conocimiento, Empresas y Universidad of the Junta de Andalucía Consejo Superior de Investigaciones Científicas State Agency for Research of the Spanish MCIU JSPS KAKENHI Program for Promoting Researches on the Supercomputer Fugaku National Astronomical Observatory of Japan Brain Pool Program
Subject
Astronomy and Astrophysics
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