V2109 Oph (1969 nova) undergoing a dwarf-nova outburst http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia21dza/ ZTF data: Slowly rising. The orbital period appears to be long, which would explain why dwarf-nova outbursts occur less than 50 years after the nova eruption. YYYYMMDD(UT) mag observer 20210522.6098 <161C (Masayuki Moriyama) 20210529.5639 <162C (Masayuki Moriyama) 20210708.2728 18.919zg (Zwicky Transient Facility Lasair (Masci+ 2019)) 20210711.2099 18.779zg (Zwicky Transient Facility Lasair (Masci+ 2019)) 20210717.2314 18.482zg (Zwicky Transient Facility Lasair (Masci+ 2019)) 20210728.2110 17.740zg (Zwicky Transient Facility Lasair (Masci+ 2019)) 20210804.1900 17.560zg (Zwicky Transient Facility Lasair (Masci+ 2019)) 20210813.1726 17.119zg (Zwicky Transient Facility Lasair (Masci+ 2019)) 20210813.1896 16.475zr (Zwicky Transient Facility Lasair (Masci+ 2019)) 20210815.2105 16.839zg (Zwicky Transient Facility Lasair (Masci+ 2019)) 20210821.1747 17.021zg (Zwicky Transient Facility Lasair (Masci+ 2019))