Light curves of the latest FUor: Indication of a close binary

摘要

We monitored the recent FUor 2MASS J06593158-0405277 (V960?Mon) since November 2009 at various observatories and multiple wavelengths. After the outburst by nearly 2.9?mag in r around September 2014 the brightness gently fades until April 2015 by nearly 1?mag in U and 0.5?mag in z. Thereafter the brightness at λ> 5000 ? was constant until June 2015 while the shortest wavelengths (U,B) indicate a new rise, similar to that seen for the FUor V2493 Cyg (HBC722). Our near-infrared (NIR) monitoring between December 2014 and April 2015 shows a smaller outburst amplitude (~2?mag) and a smaller (0.2–0.3?mag) post-outburst brightness decline. Optical and NIR color–magnitude diagrams indicate that the brightness decline is caused by growing extinction. The post-outburst light curves are modulated by an oscillating color-neutral pattern with a period of about 17 days and an amplitude declining from ~0.08?mag in October 2014 to ~0.04?mag in May 2015. The properties of the oscillating pattern lead us to suggest the presence of a close binary with eccentric orbit.