Detection of OH maser emission in the 71-year periodic comet 12P/Pons-Brooks using the 40-m Thai National Radio Telescope (TNRT)
Authors
Nobuyuki Sakai
Saran Poshyachinda
Koichiro Sugiyama
Wiphu Rujopakarn
Boonrucksar Soonthornthum
Apichat Leckngam
Busaba Kramer
Phrudth Jaroenjittichai
Bannawit Pimpanuwat
Dan Singwong
Kitipoom Kanjana
Nikom Prasert
Songklod Punyawarin
Spiro Sarris
Teep Chairin
Kamorn Bandudej
Chalunthon Nuchur
Haseng Sani
Nattawit Chanwedchasart
Pathit Chatuphot
Prachayapan Jiraya
Saharat Sathipjan
Adirake Eakwan
Chayanin Larkaew
Settasak Naewchan
Pichate Pha-Kham
Siritida Duangbuppha
Thodsawat Chaichana
Attapon Bunwong
Panupan Doomcome
Anya Poonnawatt
Warakorn Noisapung
Pathorn Sathapornvajana
Naphat Yawilerng
Thita Dilokthanakul
Kritsada Angkaew
Nattawut Chaiwongwan
Jittimat Khanchaiyapoom
Hideyuki Kobayashi
Yu-An Chen
Nawamin Intrarat
Gundolf Wieching
Ewan Barr
Jason Wu
Niclas Esser
Tobias Winchen
Pablo Vicente
Abstract
Although the optical cometary database is extensive, the radio database is limited. The 18-cm OH maser observations of comets allow us to determine (i) the production rate of OH ($Q_{\rm{OH}}$) and (ii) the water expansion velocity, for each comet. To reveal the physical properties of the periodic comet 12P/Pons-Brooks, we conducted the OH maser observations of the comet using the 40-m TNRT (Thai National Radio Telescope) on March 22nd, 27th and 29th, 2024 before the perihelion passage on April 21st, 2024. We successfully detected 1665 and 1667 MHz OH maser emissions from the comet. The average OH production rates of 12P/Pons-Brooks were determined as 4.28$\pm$0.30 $\times$ 10$^{29}$ sec$^{-1}$, 5.21$\pm$0.42 $\times$ 10$^{29}$ sec$^{-1}$, and 3.36$\pm$0.43 $\times$ 10$^{29}$ sec$^{-1}$ for March 22nd, 27th and 29th, respectively. Combining our results with previous estimates, we find that the OH production rate of 12P/Pons-Brooks shows some fluctuations on timescales of a few days, but gradually increases on longer timescales as the comet approaches the last perihelion. The water expansion velocities of the comet were determined to be 1.55$\pm$0.14 km s$^{-1}$, 1.55$\pm$0.35 km s$^{-1}$, and 2.02$^{+0.47}_{-0.45}$ km s$^{-1}$ for the observations on March 22nd, 27th and 29th, respectively. The reason why the errors are different is because the signal to noise ratio is different for each OH maser emission. All expansion velocities are consistent with the individual results of the heuristic law (Tseng et al. 2007) within errors.
