Bright nova V572 Vel Has Orbital Period of 0.12317997 +- 0.00000010 days
ATel #17254; Bradley E. Schaefer (Louisiana State University)
on 28 Jun 2025; 06:48 UT
Credential Certification: Bradley E. Schaefer (schaefer@lsu.edu)
The bright nova V572 Vel (CBET #5574, ATel #17252) was discovered by J. Seach and also by A. Pearce (both in Australia) with it currently at V=4.9 and still rising. S. Otero (VSX) reports that the likely progenitor is seen with Gaia as a blue variable at G=18.21.
TESS has light curves in Sectors 9 and 10 (early 2019), 36 and 37 (early 2021), 63 and 64 (early 2023), as well as 90 (early 2025). I have extracted the RC light curves from a 3x3 pixel photometry aperture centered on the latest coordinates, with a total of 42,940 fluxes. Fourier transforms for each and every Sector shows a highly significant and isolated peak, all for a period near 0.12318 days. This periodicity is stable and coherent across the 4 years of data. The folded light curve appears close to a simple sinewave. (A double period near 0.24636 days is ruled out because the odd/even minima are closely identical in shape and depth.) My chi-square fit to all 42,940 fluxes from all 7 Sectors gives the period to be 0.12317997 +- 0.00000010 days, and an epoch of minimum light to be BJD 2460040.0650. These data can strongly reject all the 2-year aliases. As a stable and coherent periodicity seen in all 7 Sectors, this must be the orbital period. With the orbital period of 2.956 hours, this nova is somewhat above the nova period gap, with a common period. With this orbital period, V572 Vel must have a companion star that is like a low-mass main sequence star, and such do not have winds or shells that can provide the outside material for external shocks to create the gamma-ray emission seen by Fermi (ATel #17252). So the gamma emission must be coming from internal shocks within the ejecta itself.
For two months in 2023 (Sectors 63 and 64) only, V572 Vel displayed two weak transient periodicities, at 0.105495 and 0.156470 days, of unknown origin.
