Alert Notice 451: Monitoring of the Symbiotic Variable RT Cru Requested

January 27, 2012: The symbiotic variable RT Cru has brightened in hard x-rays. Dr. Jeno Sokoloski, Columbia University, has requested AAVSO assistance in monitoring RT Cru both now and in the future to see if it is doing anything unusual in the optical. The Swift/BAT hard X-ray light curve shows RT Cru has apparently been gradually brightening over the past few years.  

Dr. Sokoloski writes: "The hard X-ray emission from RT Cru suggests that the accreting white dwarf is close to the Chandrasekhar limit (e.g., Luna and Sokoloski 2007, "The Nature of the Hard X-Ray-Emitting Symbiotic Star RT Cru") and that it is therefore a candidate supernova Type-Ia progenitor.  Also, since it is a massive white dwarf accreting at a reasonably high rate, it is similar to T CrB - so why isn't it a recurrent nova??

"Fast photometry (to look for CV-like flickering from the accretion disk) and optical spectroscopy would also be very interesting and could potentially help us interpret the current hard X-ray brightening."

Dr. Sokoloski requests time series photometry now for a few days, and then weekly or monthly observations for the forseeable future. Visual observations are also welcome. At magnitude B=10.7 and R=11.100 it is too faint for BVRI photoelectric photometry, but at magnitude J=6.646 and H=5.583 it may be a suitable target for near-IR photometrists.

Coordinates: R.A. 12 34 53.74 Dec. -64 33 56.0 (2000.0)

Finder charts may be made using VSP (

Please report your observations to the AAVSO International Database using the name "RT CRU".

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

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