Alert Notice 503: Request for regular monitoring of the symbiotic variable RT Cru

Notes:  Please continue to monitor RT Cru as it continues to decline slowly from its outburst that began in 2021 and after it returns to minimum.  -  Elizabeth O. Waagen, April 4, 2023; July 2, 2024

This campaign has been extended indefinitely. Dr. Karovska requests monitoring of RT Cru until further notice.  -  Elizabeth O. Waagen, 17 April 2020

Discussion forum thread created for this campaign at Campaigns and Observation Reports:  -  Elizabeth O. Waagen, 21 May 2020

Campaign extended through 2018. Also, campaign updated in Special Notice #409 (20151030)  and Special Notice #411 (20151215).

August 6, 2014: Dr. Margarita Karovska (Harvard-Smithsonian Center for Astrophysics) and colleagues have requested AAVSO observer assistance in their campaign on the symbiotic variable RT Cru. Weekly or more frequent monitoring beginning now is requested in support of upcoming Chandra observations still to be scheduled.

Dr. Karovska writes: "RT Cru is a fascinating member of a new class of hard X-ray emitting symbiotic binaries. The RT Cru system contains a high-mass white dwarf accreting from a mass-losing M giant. The white dwarf is surrounded by an accretion disk fed by the wind of the red giant.

"We plan Chandra observations of RT Cru in the near future that will help us understand the characteristics of the accretion onto the white dwarf in this sub-class of symbiotics. This is an important step for determining the precursor conditions for formation of a fraction of asymmetric Planetary Nebulae, and the potential of symbiotic systems as progenitors of at least a fraction of Type Ia supernovae.

"RT Cru is an optically variable source and has been observed sporadically, with a higher concentration of observations during a recent outburst from a couple of years ago. We are requesting regular optical monitoring (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 is currently 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 be created using the AAVSO Variable Star Plotter (VSP, Photometrists should use the photometry table provided there for RT Cru.

Please submit observations to the AAVSO International Database using the name RT CRU.

This campaign is being followed on the AAVSO Observing Campaigns page (

Many thanks for your contributions to this campaign!

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


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