Alert Notice 645: Monitoring of LPVs for Maser Study

Note: This campaign has been extended to October 2020 and the list of targets has been revised. Please see AAVSO Alert Notice 687 for details. - Elizabeth O. Waagen, December 4, 2019

July 31, 2018: Michael Stroh (Ph.D. candidate, University of New Mexico) requests AAVSO assistance in monitoring 19 LPVs in support of a VLA campaign studying SiO masers. AAVSO monitoring begins now and goes through October 2019.

Stroh writes: "We have an approved Karl G. Jansky Very Large Array (VLA) monitoring campaign beginning in October of 2018 lasting for one year and observations from AAVSO would be invaluable. In particular, we believe that the strengths of the SiO maser lines we observe at 43 GHz in the radio are correlated with the phase of the stars in our sample and may allow us to probe the density in the stellar envelopes. Our VLA observations will likely occur about once every 3 weeks, thus AAVSO sampling of targets ranging from 2 to 4 weeks will guide our interpretation of the radio observations.

"We selected our stars based on previous SiO observations of these sources but we also tried to select some that already had a history of good AAVSO coverage. These stars were previously observed as part of the Bulge Asymmetries and Dynamical Evolution survey and more information can be found at www.phys.unm.edu/~baade/index.html. All stars are also in the International Variable Star Index [VSX].

"Observations occurring every 2-4 weeks are preferred.

"We prefer Johnson V photometry for all stars to standardize our measurements. If this is not possible, redder filters are preferred (if possible), and are considered a bonus if performed in addition to observations in V since these are very red stars.

"All targets are in the Galactic Plane which could make some of these stars challenging to obtain good photometry. But since these are among the brightest sources in our radio observations, they may be relatively close and may not suffer from large amounts of extinction."

Observations beginning now are requested in order to have a good baseline for all the targets, especially those which have had little or no previous AAVSO coverage. As said above, observations every 2-4 weeks are requested. However, the usual cadence for LPVs is one observation every 10 days, and this cadence is requested by the AAVSO. It is asked that more frequent observations not be made.

Visual observations are welcomed and encouraged.

Charts with comparison star sequences for each of the targets above may be created using the AAVSO Variable Star Plotter (VSP).

Please submit observations to the AAVSO International Database using the names given in the table.

AAVSO Forums: This campaign is the topic of the AAVSO Campaigns and Observation Reports forum thread https://www.aavso.org/lpv-maser-2018-campaign and the Long Period Variables forum thread https://www.aavso.org/lpv-maser-2018-campaign-01

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.
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