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black hole binary

Alert Notice 624: Observations requested for ASASSN-18ey = MAXI J1820+070

March 19, 2018: Drs. Gregory Sivakoff (University of Alberta), Poshak Gandhi (University of Southampton), and Diego Altamirano (University of Southampton) have requested AAVSO observers' assistance in monitoring the new black hole X-ray binary candidate ASASSN-18ey = MAXI J1820+070.

AAVSO observers contribute to understanding the black hole binary V404 Cygni

Four AAVSO members listed as co-authors in Nature paper

V404 Cygni has been known as a variable star residing in the constellation Cygnus since the 18th century. It was believed to be a nova, a compact binary system containing a white dwarf primary and a sun-like secondary star, that undergoes unpredictable episodes of dramatic brightening - or 'outbursts' - before settling back down to quiescence for decades, until the next outburst. 

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