Astron. Astrophys. Suppl. Ser. 141, 185-192

Investigation of the H₂O maser emission in G43.8-0.1

E.E. Lekht^1,2

Send offprint request: E.E. Lekht

1 - Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis Enrique Erro No. 1, Apdo Postal 51 y 216, 72840 Tonantzintla, Puebla, Mexico
2 - Sternberg Astronomical Institute, 13 Universitetskij prospekt, Moscow 119899, Russia

Received December 8, 1998; accepted August 6, 1999

Abstract:

Observations and analysis of the H₂O maser emission source, associated with the star-forming region G43.8-0.1, are presented. The observations were carried out on the RT-22 radio telescope of the Pushchino Radio Astronomy Observatory (Russia) in 1994-1998. A new flare of emission of a group of features at radial velocities from 37.5 to 39.5 km s^-1, which took place in 1996-1998, was observed. For the 38.2 km s^-1 feature, a dependence between flux density and linewidth ( $\ln F\propto\Delta V^{-2}$) was derived; it indicates that the maser is unsaturated or partly saturated.

The evolution of emission of the 42.2 km s^-1 maser condensation is traced at a timespan of 16 years. The flux density was plotted versus linewidth for this feature (in the $\ln F,\,\Delta V^{-2}$ coordinates). This dependence contains two branches, largely shifted with respect to each other. The transition from one branch to the other took 2.5 years, while the linewidth was fluctuating. Possible causes of existence of the two branches in the maser emission evolution are discussed.

An analysis of the entire data set for 1976-1998 has shown that the time interval between the minima of integral flux in G43.8-0.1 was 18 $\pm$ 1  yr. This figure can be taken as the period of the H₂O maser activity in G43.8-0.1.

Key words: masers -- stars: formation -- radio lines: stars