High Angular Resolution Observations of the 6.7GHz Methanol Maser Toward IRAS 18440-0148

We present interferometric observations of the 6.7 GHz methanol maser toward lRAS 18440–0148, conducted with MERLIN radio interferometer. This study aims to identify and determine the absolute position, velocity, and intensity of the 6.7 GHz maser emission in this region. Our results indicate that the central maser position is located at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\alpha=18:46:36.6025,\ \delta=-01:45:22.593$</tex>. The velocity distribution of the detected maser spots spans 100 to 110 km<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>, with a systematic velocity of 97 km<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>. The maser distribution is resolved for the first time, elongated NW-SE with a velocity gradient of approximately 0.0125 km<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>/au. The brightest maser spot, with an intensity of 1.8 Jy, is found at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{V}_{\text{lsr}}\approx 105\ \text{km}^{-1}$</tex>. A comparison with previously reported observations suggests variability in maser intensity over time. This study contributes to a better understanding of the physical conditions and kinematics traced by methanol masers and provides insights into the evolutionary status of the IRAS 18440–0148 region.