Positional Offsets Between SiO Masers in Evolved Stars and their Cross-Matched Counterparts. (arXiv:1811.04511v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Pihlstrom_Y/0/1/0/all/0/1">Ylva M. Pihlström</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sjouwerman_L/0/1/0/all/0/1">Loránt O. Sjouwerman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Claussen_M/0/1/0/all/0/1">Mark J Claussen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Morris_M/0/1/0/all/0/1">Mark R. Morris</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rich_R/0/1/0/all/0/1">R. Michael Rich</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Langevelde_H/0/1/0/all/0/1">Huib Jan van Langevelde</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Quiroga_Nunez_L/0/1/0/all/0/1">Luis Henry Quiroga-Nuñez</a>
Observations of dust-enshrouded evolved stars selected from infrared catalogs
requiring high positional accuracy, like infrared spectroscopy or long baseline
radio interferometric observations, often require preparational observational
steps determining a position with an accuracy much better than 1″. Using
phase-referencing observations with the Very Large Array at its highest
resolution, we have compared the positions of SiO 43 GHz masers in evolved
stars, assumed to originate in their infrared detected circumstellar shells,
with the positions listed in the MSX, WISE, 2MASS, and Gaia catalogs. Starting
from an MSX position it is, in general, simple to match 2MASS and WISE
counterparts. However, in order to obtain a Gaia match to the MSX source it is
required to use a two-step approach due to the large number of nearby
candidates and low initial positional accuracy of the MSX data. We show that
the closest comparable position to the SiO maser in our limited sample never is
the MSX position. When a plausible source with a characteristic signature of an
evolved star with a circumstellar shell can be found in the area, the best
indicator of the maser position is provided by the Gaia position, with the
2MASS position being second-best. Typical positional offsets from all catalogs
to the SiO masers are reported.
Observations of dust-enshrouded evolved stars selected from infrared catalogs
requiring high positional accuracy, like infrared spectroscopy or long baseline
radio interferometric observations, often require preparational observational
steps determining a position with an accuracy much better than 1″. Using
phase-referencing observations with the Very Large Array at its highest
resolution, we have compared the positions of SiO 43 GHz masers in evolved
stars, assumed to originate in their infrared detected circumstellar shells,
with the positions listed in the MSX, WISE, 2MASS, and Gaia catalogs. Starting
from an MSX position it is, in general, simple to match 2MASS and WISE
counterparts. However, in order to obtain a Gaia match to the MSX source it is
required to use a two-step approach due to the large number of nearby
candidates and low initial positional accuracy of the MSX data. We show that
the closest comparable position to the SiO maser in our limited sample never is
the MSX position. When a plausible source with a characteristic signature of an
evolved star with a circumstellar shell can be found in the area, the best
indicator of the maser position is provided by the Gaia position, with the
2MASS position being second-best. Typical positional offsets from all catalogs
to the SiO masers are reported.
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