Detection of an 11-Minute Period in the X-ray SSS light curve of the Nova V572 Vel

ATel #17603; Jan-Uwe Ness (ESA-ESAC), Marina Orio (University of Wisconsin and INAF-Padova), Andrej Dobrotka Slovak University of Technology in Bratislava), Gerardo Juan Manuel Luna (CONICET-University of Buenos Aires), Kim L. Page (U. Leicester), Andy P. Beardmore (U. Leicester), Julian Osborne (U. Leicester)
on 15 Jan 2026; 17:43 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Jan-Uwe Ness (juness@sciops.esa.int)

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The nova V572 Vel has been observed for a duration of 39.1ks with XMM-Newton starting on UT 2025-11-28.3, 155.86 days after discovery (tref=June 25.440 UT). We report the presence of a strong, coherent periodic oscillation of 661.88s +/- 0.46s in all five simultaneous X-ray light curves, namely with the EPIC/pn (Timing Mode, Thick filter), EPIC/MOS1 (Small Window, Medium Filter), EPIC/MOS2 (Timing Mode, Medium Filter), RGS1 and RGS2. The shape of the phased light curve is sinusoidal, and no overtones are detected. The amplitude is ~10% in all light curves. The Optical Monitor (OM) located the source at the coordinates R.A. = 10h25m13s.90, Decl. = -53d31'18".9 (equinox J2000.0) which are consistent with the ones reported by K. Yoshimoto, Yamaguchi rather than those reported earlier by John Seach, Grafton being 20" off, see005574.txt."> http://www.cbat.eps.harvard.edu/cbet/005500/CBET005574.txt. Unfortunately we do not have a UV light curve due to a technical error resulting from assuming the Grafton coordinates. We attempted to confirm the period independently with Swift XRT but caution that the majority of the Swift-XRT data have been collected in short snapshots, most shorter than this 11-min period. A Lomb Scargle periodogram combining all the Windowed Timing data between 140-186 days after tref, when the XRT count rate was >5 count/s, confirms the XMM-Newton period, with an amplitude that reaches 10-20%. Folding the XRT data over shorter durations (up to 1e6s in length) at the 11 min period indicates the modulation is present throughout the interval covered by these XRT observations. The SSS is still bright on 14 January 2026. The RGS detects an atmospheric continuum spectrum, typical of other SSS, resembling most the very low-temperature V339 Del (see, e.g. ATel #5593). The continuum covers the wavelength range from ~23-38AA (38AA is the end of the spectral coverage of RGS) containing several absorption features, most prominently the CV absorption edge at 31.62A and, weaker, the CVI absorption edge at 25.3AA, plus several absorption lines including CV, CVI, NVI, and NVII, blue-shifted by ~1600km/s.