Detection of OH Maser Emission in the 71 yr Periodic Comet 12P/Pons-Brooks Using the 40 m Thai National Radio Telescope

Monday 1 Dec 2025, 13:30 → 13:50 Europe/Rome

0/0-3 - Sala Rosino (Dipartimento di Fisica e Astronomia - Edificio ex-Rizzato)

Speakers: Alessandra Mura (Università degli Studi di Padova)

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_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 Thai National Radio Telescope on 2024 March 22, 27, and 29, before the perihelion passage on 2024 April 21. 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 ± 0.30 × 10²⁹ s⁻¹, 5.21 ± 0.42 × 10²⁹ s⁻¹, and 3.36 ± 0.43 × 10²⁹ s⁻¹ for March 22, 27, and 29, 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 ± 0.14, 1.55 ± 0.35, and 2.02 −0.45+0.47 km s⁻¹ for the observations on March 22, 27, and 29, 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 within errors.

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