Alert Notice 558: CI Aql monitoring needed to support HST observations

October 19, 2016: Dr. Edward Sion (Villanova University) has requested AAVSO observers' assistance in monitoring the recurrent nova CI Aql in support of observations with the Hubble Space Telescope Cosmic Origins Spectrograph scheduled for October 31 - November 2, 2016, and November 3 - November 5, 2016. These observations are part of a study on short orbital period recurrent novae as Supernovae Type Ia progenitors.

It is essential to know 24 hours prior to the HST COS observations that CI Aql is not in outburst, in order to protect the instrumentation. Observers are asked to keep an eye on CI Aql with nightly snapshot images (V preferred) from now until November 12, and to report their observations promptly. It will be especially important to know the brightness of CI Aql each night for October 28 through November 7 UT. Visual observations are welcome.

CI Aql (Nova Aql 1917) has had recurrent outbursts in 1941 and 2000, brightening to V~8.5. At minimum it is V~16-16.5 or fainter.

Coordinates (2000.0): R.A. 18 52 03.57  Dec.  -01 28 39.4

Charts with a comparison star sequence for CI Aql may be created using the AAVSO Variable Star Plotter (VSP). Observers need to be aware that the field of view is complicated by some comparison stars appearing as close doubles.

Please submit observations to the AAVSO International Database using the name CI AQL.

This campaign is being followed on the AAVSO Observing Campaigns webpage. A thread has been created on the Campaigns and Observation Reports forum at (https://www.aavso.org/content/ci-aql-observing-campaign).

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

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