AAVSO Alert Notice 680 announces a campaign on the faint white dwarf J0139 (ZTF J013906.17+524536.89). Please see the notice for details and observing instructions.
Please note the short name is J0139, NOT J1039 as originally announced by me!
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
J0139 is a white dwarf that fades ever 108 days. Each fade can last a week or longer so they are thought to be produced by large dust clouds surrounding a planetesimal in an eccentric, 108-day orbit. Last Fall I asked for AAVSO observations of this star to verify the 5th fade event. Seven AAVSO observers responded, and 3 produced observations that confirmed the 5th fade, which occurred in 2019 October. The next expected fade in 2020 January didn't occur. Amazing! This is still a puzzle. This season's observing season for J0139 has ended, so it's an appropriate time for me to thank the 7 AAVSO observers for their submissions: TRT, SPP, DFS, VMT, LPAC, SDM & SABB. This 18.4-mag target was a challenging object, and I want to especially thank TRT, SPP & DFS for some good quality observations. I have notified the professional astronomer who discovered the J0139 fades about the AAVSO observations, Dr. Zachary Vanderbosch (Univ. Texas), so he may contact some of you for additional information. My role in this project is ending, so I am concluding this AAVSO J0139 campaign. Thanks again for answering this call for observations of a most difficult target.