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Possible Detection of Quasi-Periodic Oscillations from Sgr A* at 43 GHz

Published online by Cambridge University Press:  09 February 2017

Yuhei Iwata ,
Tomoharu Oka  and
Makoto Miyoshi
Yuhei Iwata
Affiliation:
Department of Physics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa, Japan email: iwa-astro4338@z3.keio.jp
Tomoharu Oka
Affiliation:
Department of Physics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa, Japan email: iwa-astro4338@z3.keio.jp
Makoto Miyoshi
Affiliation:
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, Japan
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Abstract

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Quasi-periodic oscillations (QPOs) are believed to be indirect evidence for black holes. Several authors have reported detections of QPOs from Sgr A*, the nucleus of our Galaxy, in infrared and X-ray wavelength during flare-ups. Miyoshi et al. (2011) reported a tentative detection of QPOs in the 43 GHz light curve of Sgr A* obtained with the Very Long Baseline Array (VLBA). To confirm their detection, we reanalysed their VLBA data very conservatively. The 43 GHz flux was calculated for every 15 seconds by assuming a two-dimensional Gaussian-shape spatial structure. The Lomb-Scargle periodogram of the 43 GHz flux just after a millimeter wave flare of Sgr A*, shows three apparent peaks at 10.2, 14.6 and 32.1 min. Two of them are barely consistent with the previously reported QPOs. Using the resonant oscillation model, we estimated the spin parameter of the Sgr A* black hole to be 0.56 assuming the mass of 4.3 × 106M⊙.

Keywords

accretionaccretion disksblack hole physicsGalaxy: center
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , Symposium S322: The Multi-Messenger Astrophysics of the Galactic Centre , July 2016 , pp. 50 - 51
Copyright
Copyright © International Astronomical Union 2017 

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