------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 3139 2016 Jan 22 11.16UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074 INTERNET: GUY@TAHQ.DEMON.CO.UK Backup: gmh@wdcc1.bnsc.rl.ac.uk WORLD WIDE WEB http://www.theastronomer.org ------------------------------------------------------------------- R AQR OBSERVING CAMPAIGN Elizabeth Waagen advises us via AAVSO alert 535: Dr. George Wallerstein (University of Washington) has requested coverage of the long period/symbiotic variable R Aquarii beginning immediately in support of high resolution spectroscopic observations planned for 2016 January 19 and 21. Several other astronomers, including Drs. Lee Anne Willson (Iowa State University), Ulisse Munari (INAF, Astronomical Observatory of Padua, Italy), and Fred Walter (Stony Brook University) are studying R Aqr closely and additional spectroscopic and other observations are planned for the near future. R Aqr is an extremely interesting system. Its type is both Mira (M) and symbiotic (ZAND) - it is a close binary system consisting of a hot star and a late-type star (the Mira), both enveloped in nebulosity. As a result, the very interesting light curve shows not only the Mira pulsation but also complex eclipse behaviour as the two stars interact. The period of Mira variation is 387.0 days; the eclipse period is 43.6-44 years. The cause of the eclipse is unknown; several theories have been proposed, including a focused accretion stream, a disk or cloud around the secondary, and a triggered mass loss that produces an opaque cloud. Careful investigation of this upcoming event should help to resolve this question. The last eclipse of R Aqr was in 1978. The next eclipse is predicted for 2022, but may be early. The current behaviour of R Aqr suggests that the eclipse, which lasts for several years, may either be beginning or its beginning may be imminent. R Aqr was at minimum in early December 2015 at magnitude V=11.4, and is currently at visual magnitude 11.0. During this phase of the approximately 44-year eclipse cycle, at maximum it may be as bright as V~6.0-6.5 but is not expected to become brighter. Beginning immediately, nightly BVRI CCD and DSLR photometry and visual observations are requested. As R Aqr brightens towards maximum and is in range, PEP observations are also requested. Ongoing spectroscopy over the next several years will be interesting to see as the system evolves throughout the eclipse. Coordinates (J2000): R.A. 23 43 49.46  Dec. -15 17 04.2 Charts with a comparison star sequence for R Aqr may be created using the AAVSO Variable Star Plotter (VSP; https://www.aavso.org/vsp). Please report all observations to the AAVSO International Database using the name "R AQR". Editor: Please copy these results monthly to Gary Poyner as part of your TA report. Guy M Hurst