AAVSO Alert Notice 503
August 6, 2014
Request for regular monitoring of the symbiotic variableRT Cru
Current magnitude 12 -12.5.
Dr. Margarita Karovska (Harvard-Smithsonian Center forAstrophysics) and colleagues have requested AAVSO observer assistance in theircampaign on the symbiotic variable RT Cru. Weekly or more frequent monitoringbeginning now is requested in support of upcoming Chandra observations still tobe scheduled.
Dr. Karovska writes: "RT Cru is a fascinating memberof a new class of hard X-ray emitting symbiotic binaries. The RT Cru systemcontains a high-mass white dwarf accreting from a mass-losing M giant. The whitedwarf is surrounded by an accretion disk fed by the wind of the red giant.
"We plan Chandra observations of RT Cru in the nearfuture that will help us understand the characteristics of the accretion ontothe white dwarf in this sub-class of symbiotics. This is an important step fordetermining the precursor conditions for formation of a fraction of asymmetricPlanetary Nebulae, and the potential of symbiotic systems as progenitors of atleast a fraction of Type Ia supernovae.
"RT Cru is an optically variable source and has beenobserved sporadically, with a higher concentration of observations during arecent outburst from a couple of years ago. We are requesting regular opticalmonitoring (B and V photometry) of this source (on a weekly basis if possible)."Visual observations are also encouraged.
RT Cru varies between 11.2 and 12.6 visual; it iscurrently V magnitude 11.964 (2014 Aug 5.9631 UT, JD 2456875.4631; HMB, J.
Hambsch, Mol, Belgium, remotely from Chile).
Coordinates: R.A. 12 34 53.74 Dec. -64 33 56.1 (2000.0)
Charts for RT Cru with comparison star sequence may becreated using the AAVSO Variable Star Plotter (VSP, http://www.aavso.org/vsp
). Photometristsshould use the photometry table provided there for RT Cru.
Please submit observations to the AAVSO InternationalDatabase using the name RT CRU.
Many thanks for your contributions to this campaign!
This AAVSO Alert Notice was compiled by Elizabeth O.Waagen.