An ongoing fade of the cataclysmic variable WX Arietis

ATel #12139; Colin Littlefield (University of Notre Dame), Katherine Hill (Bishop McGuinness Catholic High School; University of Notre Dame Pre-College Summer Scholars Astronomy Program)
on 23 Oct 2018; 00:03 UT
Credential Certification: Colin Littlefield (clittlef@alumni.nd.edu)

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V-band observations by the All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al. 2014, ApJ, 788, 48; Kochanek et al. 2017, PASP, 129, 104502) show that the cataclysmic variable WX Arietis (hereinafter, WX Ari) faded by ~0.3 magnitudes at some point during its solar conjunction in 2018 and then by another ~0.3 magnitudes in early-to-mid August 2018. Since then, it has remained stable near V~15.3, consistent with a drop in the binary's mass-transfer rate. A well-known member of the SW Sextantis class of cataclysmic variables, WX Ari is an eclipsing novalike system and is normally characterized by a high mass-transfer rate (see D. W. Hoard's "Big List of SW Sextantis Stars" at https://www.dwhoard.com/biglist; Hoard et al. 2003, AJ, 126, 2473).

To assess the notability of the current fading episode, we retrieved the long-term light curve of WX Ari from the Catalina Real-Time Transient Survey (CRTS; Drake et al. 2009, ApJ, 696, 870) and combined it with the ASAS-SN V-band light curve, obtaining a baseline of observations that extends back to 2005. In addition to showing that WX Ari spends most of its time near V~14.7, the combined light curve contains three low states: a pair of extremely faint states with a maximum depth of over 2.5 mag, and a partially observed low state in 2005 that was only 0.5 mag deep. The two extremely low states, which lasted from 2012-2013 and 2013-2016, were separated by a temporary bright state during which WX Ari returned to its typical luminosity. It is unclear whether the ongoing fade is simply a shallow low state (similar to the 2005 event) or a prelude to an extremely faint state, but continued ASAS-SN observations should provide the answer.

The linked figure is a two-page PDF containing (1) the combined ASAS-SN/CRTS light curve and (2) the ASAS-SN V- and g-band light curve from 2018 only. The large gap in the latter is due to solar conjunction.

The Notre Dame Pre-College Summer Scholars Astronomy Program made possible K.H.'s involvement with this work.

Figure: WX Ari light curves