Optical fading of the intermediate polar FO Aquarii
ATel #12860; M. R. Kennedy (JBCA / Uni. of Manchester), R. P. Breton (JBCA / Uni. of Manchester), C. Littlefield (Uni. of Notre Dame), P. M. Garnavich (Uni. of Notre Dame), F.-J. Hambsch (AAVSO / VVS / BAV / Center for Backyard Astrophysics), V. Dhillon (University of Sheffield), T. Butterley (Uni. of Durham), R. Wilson (Uni. of Durham), S. Littlefair (Uni. of Sheffield), D. Steeghs (Warwick University), D. K. Galloway (Monash University), P. O'Brien (Uni. of Leicester), G. Ramsay (Armagh Observatory & Planetarium), D. Pollacco (Warwick University), E. Thrane (Monash University), S. Poshyachinda (National Astronomical Research Institute of Thailand), K. Ulaczyk (Warwick University), K. Ackley (Monash University), M. Dyer (University of Sheffield), E. Rol (Monash University), J. Lyman (Warwick University)
on 11 Jun 2019; 09:49 UT
Credential Certification: Mark Kennedy (kennedy.mark@manchester.ac.uk)
Subjects: Optical, Cataclysmic Variable
The intermediate polar FO Aquarii has been observed to fade at optical wavelengths over the last 10 days (see the attached light curve). Observations taken using the pt5m telescope (V band), the Gravitational Optical Transient Observatory (GOTO; L band covering 400-700 nm), the All-Sky Survey for Supernovae (ASAS-SN; Shappee et al. 2014; Kochanek et al. 2017; g band), and the Remote Observatory Atacama Desert (ROAD; V band) all show that FO Aquarii is currently fainter than its typical high state magnitude in these bands. In particular, in V-band the source is currently varying between 14.0-14.65, compared to its typical range of 13.4-13.9 during normal high states.
This suggests that FO Aquarii has entered another low state, the 4th in 3 years (Littlefield et al. 2016, ApJ, 833, 93; Littlefield et al. 2018, ATel #11844). A power spectrum of the V band data obtained within the last 5 days shows strong power at the 23 min beat period of the system, consistent with behaviour seen in previous low states. Optical monitoring of the source (both high time cadence photometry and spectroscopy) is highly encouraged, as the sudden onset of a deep low state may occur, in which FO Aquarii will fade by at least another 2 magnitudes (the true depth of a deep low state in FO Aquarii is currently unknown). Identification and detailed observations of such a low state are important in constraining the change of accretion geometry which may occur during these low states.
1 year light curve for FO Aquarii
