Alert Notice 635: Monitoring of SDSS J141118.31+481257.6 requested

May 25, 2018: Dr. Thomas Kupfer (University of California, Santa Barbara) has requested AAVSO assistance in monitoring the rare AMCVn binary SDSS J141118.31+481257.6 during its current WZ Sge-like outburst, the first outburst detected for this system.

The outburst was detected by Tadashi Kojima (Gunma-ken, Japan) on 2018 May 19.514 UT with a magnitude 12.6 V  +/- 0.2. At minimum brightness 19.7 CV, SDSS J141118.31+481257.6 brightened by over 6 magnitudes, reaching a peak brightness of 12.5-12.6 V.

Dr. Kupfer writes: "Over the last few days, the object faded much faster than expected. ZTF detected it last night [May 23] at 17.3mag. So, it's almost back in quiescence.

"This is very unusual and there is a chance that this is only a precursor outburst as seen in CR Boo (as similar system at even shorter period)

"If this is true I expect that within the next few days the system will start to brighten again and undergo a 'real' superoutburst where it will stay bright for a week or even longer (given its long orbital period). In this phase I would expect that we see very strong superhumps."

Observers are requested to monitor this object closely over the next one to two weeks to catch the possible rebrightening as quickly as possible. Filtered observations are preferred, but all observations are welcome. Please submit your observations to the AAVSO International Database as soon after you make them as possible. The cadence of observations will be determined by equipment and conditions, but timeseries to monitor superhumps as they evolve would be very valuable. Observers should continue to monitor the object until it has returned to minimum.

The most recent observation in the AAVSO International Database shows SDSS J141118.31+481257.6 on 2018 May 25.35343 UT at magnitude 17.427 CV +/-0.046 (J. Seitz, East Lansing, MI).

Coordinates (2000.0):  R.A. 14 11 18.32   Decl. +48 12 57.5

Charts: Charts with a comparison star sequence for SDSS J141118.31+481257.6 may be created using the AAVSO Variable Star Plotter (VSP). The AAVSO sequence is being extended at the faint end to accommodate the faint state of the variable.

Submit observations: Please submit observations to the AAVSO International Database using the name SDSS J141118.31+481257.6.

This campaign is being followed in the AAVSO Time Sensitive Alerts Forum at

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.

Information on submitting observations to the AAVSO may be found at:


An Alert Notice archive is available at the following URL:

Subscribing and Unsubscribing may be done at the following URL:


Please support the AAVSO and its mission -- Join or donate today: