Simultaneous observations of an active repeater FRB 20240114A with Lulin One-meter Telescope and FAST
Tetsuya Hashimoto1*, Tomotsugu Goto2, Chow-Choong Ngeow3, Chen-hui Niu4, Yuhao Zhu5, Tsung-Ching Yang1, Bjorn Jasper R. Raquel6, Howard Chuang1, William Chang1, Simon C.-C. Ho7, Shotaro Yamasaki1, Tzu-Yin Hsu2, Mohanraj Madheshwaran1, Yuu Niino8, Ece Kilerci9, Yu-An Chen2
1Department of Physics, National Chung Hsing University, Taichung, Taiwan
2Institute of Astronomy, National Tsing Hua University, Hsinchu, Taiwan
3Institute of Astronomy, National Central University, Taoyuan, Taiwan
4College of physics science and technology, Central China Normal University, Wuhan, China
5National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
6National Institute of Physics, University of the Philippines, Manila, Philippines
7Research School of Astronomy and Astrophysics, The Australian National University, Canberra, Australia
8Graduate School of Science, University of Tokyo, Tokyo, Japan
9Faculty of Engineering and Natural Sciences, Sabancı University, Istanbul, Turkey
* Presenter:Tetsuya Hashimoto, email:tetsuya@phys.nchu.edu.tw
The radiation mechanism of fast radio bursts (FRBs) remains unknown. Because currently-survived theoretical models can basically explain the common features of FRBs in radio, including their short timescales and extremely high brightness temperatures, solely using radio data is not effective in distinguishing FRB models. Simultaneously detected optical counterparts of FRBs are the final piece of the puzzle to uncover their mysterious radiation mechanism because major theoretical FRB models, i.e., magnetosphere and external shocks, predict significantly different optical-to-radio fluence ratios. However, the hypothetical optical counterpart is yet to be detected because FRBs disappear in ~1 ms, making the simultaneous counterpart search challenging. To overcome this problem, we take advantage of monitoring observations by the Five-hundred-meter Aperture Spherical Telescope (FAST). FAST is the most sensitive single-dish radio telescope, regularly monitoring known repeating FRB sources. Once its monitoring is scheduled, we trigger simultaneous Target-of-Opportunity (ToO) observations with the Lulin One-meter Telescope (LOT; optical) in Taiwan, using a CMOS camera with a time resolution of ~17 ms. This is one of the shortest timescales conducted by CMOS cameras for FRBs so far, enhancing the sensitivity to the optical counterpart. In 2024, we triggered two ToO observations of LOT to conduct simultaneous observations of FRB 20240114A during part of the FAST's monitoring campaign. FRB 20240114A was first discovered by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and is known as an active repeater. More than 17 (61) FRBs were detected with FAST on 7 (14) July during the LOT ToO observations. Based on the non-detection of optical counterparts to these bursts, we will present the upper limit on the optical-to-radio fluence ratios placed by our observations and discuss possible constraints on the radiation mechanisms for this particular FRB source.


Keywords: Transients, Fast radio bursts, Optical and radio observations