TESS detects stable 0.1802-day modulation in slowly-rising nova PGIR22akgylf 3-16 days post-discovery

The arXiv preprint from Sokolovsky and collaborators at Michigan State University reports TESS 2-minute cadence data covering days 3-16 after the PGIR discovery alert, supplemented by ground-based photometry that tracked the full 133-day rise. The team identified the periodic signal through Lomb-Scargle analysis and confirmed spatial-temporal coincidence with the nova position; the period remained constant, favoring an orbital rather than pulsational origin. At these epochs the photosphere had already expanded beyond the white dwarf yet remained comparable to binary separation, allowing the companion to tidally distort the envelope and imprint the observed modulation. This places common-envelope interaction as a plausible driver of mass ejection even in systems lacking a giant donor, distinguishing PGIR22akgylf from the symbiotic-nova subset previously invoked to explain slow rises.

The 0.18-day period implies a dwarf secondary and orbital separation of roughly 1-2 solar radii once the white-dwarf mass is assumed near 1 solar mass, consistent with the observed amplitude if the envelope is only modestly aspherical. Earlier TESS nova detections lacked comparable early-time coverage, so the present dataset supplies the first direct photometric probe of envelope geometry during the critical pre-maximum phase. The finding also tightens the empirical boundary between fast and slow novae by showing that slow optical rise can occur without an evolved companion.

Future radial-velocity monitoring of the post-nova remnant can test whether the photometric period equals the orbital period or half of it, while continued TESS sectors on other slow risers will reveal how common this early-time modulation is. High-cadence ultraviolet spectroscopy during the next similar event would directly map velocity fields across the distorted photosphere.