ﻻ يوجد ملخص باللغة العربية
We present results of multi-epoch VLBI observations with VERA (VLBI Exploration of Radio Astrometry) of the 22 GHz H$_{2}$O masers associated with a young stellar object (YSO) IRAS 22198+6336 in a dark cloud L1204G. Based on the phase-referencing VLBI astrometry, we derive an annual parallax of IRAS 22198+6336 to be 1.309$pm$0.047 mas, corresponding to the distance of 764$pm$27 pc from the Sun. Although the most principal error source of our astrometry is attributed to the internal structure of the maser spots, we successfully reduce the errors in the derived annual parallax by employing the position measurements for all of the 26 detected maser spots. Based on this result, we reanalyze the spectral energy distribution (SED) of IRAS 22198+6336 and find that the bolometric luminosity and total mass of IRAS 22198+6336 are 450$L_{odot}$ and 7$M_{odot}$, respectively. These values are consistent with an intermediate-mass YSO deeply embedded in the dense dust core, which has been proposed to be an intermediate-mass counterpart of a low-mass Class 0 source. In addition, we obtain absolute proper motions of the H$_{2}$O masers for the most blue-shifted components. We propose that the collimated jets aligned along the east-west direction are the most plausible explanation for the origin of the detected maser features.
We measured the trigonometric annual parallax of H$_2$O maser source associated with the massive star-forming regions IRAS 06061+2151 with VERA. The annual parallax of $0.496pm0.031$ mas corresponding to a distance of $2.02^{+0.13}_{-0.12}$ kpc was o
Maser emission plays an important role as a tool in star formation studies. It is widely used for deriving kinematics, as well as the physical conditions of different structures, hidden in the dense environment very close to the young stars, for exam
We present results of a multi-epoch monitoring program on variability of 6$,$cm formaldehyde (H$_2$CO) masers in the massive star forming region NGC$,$7538$,$IRS$,$1 from 2008 to 2015 conducted with the GBT, WSRT, and VLA. We found that the similar v
An overview is given of the analysis of more than a decade of H2O maser data from our monitoring program. We find the maser emission to generally depend on the luminosity of the YSO as well as on the geometry of the SFR. There appears to be a thresho
We report the detection of water maser emission from four nearby galaxies hosting ultradense HII (UDHII) regions, He 2-10, the Antennae galaxies (NGC 4038/4039), NGC 4214, and NGC 5253, with the Green Bank Telescope. Our detection rate is 100%, and a