Detection of dust in the nova V572 Velorum from SPHEREx observations

ATel #18127; D. P. K. Banerjee (Physical Research Laboratory, India), A. Evans (Keele University), C. E. Woodward (University of Minnesota), S. Starrfield (Arizona State University), Vishal Joshi (PRL, India)
on 29 Oct 2026; 16:46 UT
Credential Certification: Dipankar P.K. Banerjee (dpkb12345@gmail.com)

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V572 Velorum ( Nova Velorum 2025) was discovered by John Seach, and independently by Andrew Pearce, on 25 June 2025 (CBET 5574) at an apparent visual magnitude of 5.7. However, archival data showed that the nova had been detected earlier on 20 June 2025 by the Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) observatory (Banerjee et al., 2026, ATel #17601). It reached a peak brightness of 4.8 on June 27. The nova was also detected in gamma rays by FERMI-LAT on 2026 June 25 (Jean, P. et al, ATel #17252). Observations of the system before the 2025 explosion show the nova has already undergone several dwarf-nova outbursts with both "long" (over 13 days) and "short" (3 to 4 days) periods and is thus classified as a dwarf nova of the SU Ursae Majoris variable type (Mroz et al., 2026, ATel #17253). Mroz et al 2026 write that classical novae originating from dwarf nova progenitors are extremely rare; known examples include V1213 Cen and V392 Per. A spectrum taken of V572 Velorum on 30 June 2025 looks typical of a Fe II-type classical nova (Kaufman, R, 2026, CBET 5577). The nova has a well determined orbital period of 2.96 h (Schaefer, B.E., 2026, RNAAS, 9 (8), 213). A 11 minute period has also been found from X-ray studies (Jan- UWe Ness et al., ATel #17603, ATel #18121)

The AAVSO lightcurve of the nova shows a sudden rapid fading in the V magnitude starting from around 25 days after the discovery, fading from ~5.5 mag to ~12 mag at the lowest point of the lightcurve and then recovering. Such a rapid fading is typically associated with the formation of dust in novae. Here we confirm the formation of dust in the nova from SPHEREx archival data. The first spectrum covering 0.75-2.36 microns and showing the IR excess due to dust, covers the period JD 2461025.4823 to JD 2461072.4666 (between 178 to 225 days after t0 which is assumed to be 20 June 2025, ATel #17601). The nova had then just emerged from the deep dust dip but not all the dust had been destroyed. The dust emission can be fit by a blackbody with temperature of ~ 1030K. Assuming a carbonaceous composition, the associated dust mass is approximately 10^-09 M(sun). The second spectrum covering 0.75 to 5 micron, where the IR excess from the dust is more pronounced, spans the period between JD 2461181.7552 to JD 2461240.0709 (334 to 393 days after t0). A blackbody fit to this data indicates the dust has cooled to 480K from the earlier epoch, and had a mass of 10^-08 M(sun). Such a mass is typically observed in dust-forming classical novae. Prominent emission lines are seen in both the SPHEREx spectra arising from H, He and O - the lines are typical of those seen in novae spectra. Possibly coronal line emission is present; however, the low spectral resolution of SPHEREx inhibits clean identification of the species (resolution R ~ 40 between 0.75 to 3.8 microns and R ~110 between 3.8 to 5.0 microns). Higher resolution spectroscopy is encouraged.

This ATEL makes use of data products from the Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx), which is a joint project of the Jet Propulsion Laboratory and the California Institute of Technology, and is funded by the National Aeronautics and Space Administration.

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