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OGLE-IV Observations of ASASSN-16oh

ATel #9867; P. Mroz, A. Udalski, L. Wyrzykowski, S. Kozlowski, R. Poleski (Warsaw University Observatory), on behalf of the OGLE team
on 16 Dec 2016; 14:43 UT
Credential Certification: Przemek Mroz (pmroz@astrouw.edu.pl)

Subjects: Optical, Binary, Cataclysmic Variable, Nova, Transient

ASASSN-16oh is an unusual transient in the vicinity of the Small Magellanic Cloud (ATels #9859, #9866). The object is located in the field MBR103.17 that is regularly monitored by the OGLE-IV Survey since 2010.

The transient is located at equatorial coordinates (RA, DEC) = (01:57:43.79, -73:37:32.3) J2000.0, 0.7 arcsec from the position reported by the ASASN-SN group (ATel #9859). The mean brightness of the progenitor in quiescence was I = 20.35 and V = 21.09 mag. However, the progenitor showed irregular variability, including a 1.5-mag flare in November 2014.

The rise to the current brightness is very slow. The source has been brightening slowly (at least) since August 2016 at a mean rate of 0.02 mag/day. The rise is not linear, with low-amplitude oscillations.

The optical light curve does not resemble that of a classical nova nor a CV. Any interpretation that involves the classical nova eruption (even in an exotic binary with early-type companion) can be ruled out, because the rise is too slow.

Light curve and finding charts can be found here.