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 [1], 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 [2], "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 (http://www.aavso.org/vsp [3]).

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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