Abstract

We have carried out time monitoring observations of the 28SiO v = 0, 1, 2, J = 2 − 1, 28SiO v = 0, 1, 2, J = 3 − 2, and 29SiO v = 0, J = 3 − 2 transitions in Orion KL with the 14 m radio telescope at Taeduk Radio Astronomy Observatory. The pair of J = 2 − 1 and J = 3 − 2 transitions was simultaneously observed from 1999 January to 2001 March. Each transition shows different characteristics. Both the v = 1, J = 2 − 1, and J = 3 − 2 masers show a relatively stable double-peaked profile and little variation in intensity. The 28SiO v = 2, J = 3 − 2 maser presents the most active intensity variations including a disappearance on 2000 February 17 and 2001 February 16. The v = 2, J = 3 − 2 maser may trace the closest region to the central young stellar object and results in the strongest variations of intensity and line profile. The v = 2, J = 2 − 1 maser was not detected in the monitoring. The 28SiO v = 0, J = 3 − 2 lines showed a large variation of peak intensity compared with 28SiO v = 0, J = 2 − 1 that might be due to partial masing. The different observational results of 28SiO v = 0, 1, J = 2 − 1, 28SiO v = 0, 1, 2, J = 3 − 2, and 29SiO v = 0, J = 3 − 2 transitions might reflect that individual transitions trace different portions of gas.

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