Special Notice #409: Chandra observations scheduled for RT Cru

October 30, 2015: Further to AAVSO Alert Notice 503, Dr. Margarita Karovska (Harvard-Smithsonian Center for Astrophysics) informs us that the Chandra observations of the symbiotic variable RT Cru have been scheduled.

Dr. Karovska writes: "In addition to the continuous, regular monitoring [that observers have been providing since August 2014, we] are requesting twice-weekly or more frequent [B, V, and visual photometry and spectroscopy] throughout November 2015 in support of Chandra observations scheduled for mid-November 2015.

"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.

"The Chandra observations of RT Cru 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."

Please continue your B, V, and visual observations at least twice weekly of RT Cru through December 5. Spectroscopy would be very valuable and is strongly encouraged if at all possible. RT Cru varies between 11.2 and 12.6 visual; as of 2015 October 18.77 UT it was V=12.09(03) and B=13.48(03) (NLX, P. Nelson, Ellinbank, VIC, Australia).

Coordinates: R.A. 12 34 53.74  Dec. -64 33 56.1  (2000.0)

Charts with a comparison star sequence for RT Cru may be created using the AAVSO Variable Star Plotter (VSP).

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

Observers who are able to obtain spectra should contact Elizabeth Waagen (eowaagen@aavso.org) for instructions on how to submit their data.

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


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