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

¹ Astronomisches Institut, Ruhr–Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany
e-mail: hackstein@astro.rub.de
² Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, PO Box 67, 1525 Budapest, Hungary
³ Center for Backyard Astrophysics (Antwerp), American Association of Variable Star Observers (AAVSO), Verenigin Voor Sterrenkunde (VVS), Andromeda Observatory, Oude Bleken 12, 2400 Mol, Belgium
⁴ Instituto de Astronomia, Universidad Católica del Norte, Avenida Angamos 0610, Casilla 1280 Antofagasta, Chile
⁵ Institute for Astronomy, University of Hawaii, 640 N. Aohoku Place, Hilo, HI 96720, USA

Received: 5 August 2015
Accepted: 5 October 2015

Abstract

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 Å 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.