Discovery of a Surprising Flux Event in White Dwarf HZ 4

HZ 4 is a DA White Dwarf (WD) and a commonly-used photometric standard star. While analyzing its suitability as a UV calibrator, supplementary optical data from TESS revealed an increase in flux by 43.2%, seen only on Sector 43.[Mention the date, The event 29 hr long, the flux shape is symmetric, and the flux increase is preceded and followed by a flux decrease of 11.4%] No other objects are observed in the DSS, GALEX, or WISE images within the TESS pixel in which HZ 4. HZ4 is not in the instability strip. Furthermore, there is no evidence of HZ 4 having a binary companion in literature and no evidence of any circumstellar material based on photometry. The event does resemble a dwarf nova, although no periodicity is observed. We present here the details of this event and our findings on HZ 4.