Swift XRT/WT upper limits on the X-ray emission from Nova Vel 2025 (V572 Vel)

ATel #17262; Gerardo Luna (UNAHUR/CONICET), Marina Orio (Univ. of Wisconsin and INAF-Padova), Isabel J. Lima (UNESP), Marina M. Cunha e Mello (INPE), Fernando F. Marques (INPE)
on 3 Jul 2025; 11:36 UT
Credential Certification: Gerardo Juan Manuel Luna (juan.luna@unahur.edu.ar)

Tweet

The source V572 Vel entered into an outburst on June 25.44 (CBET #5574), reaching U=5.6 magnitudes(as reported by CBAT, http://www.cbat.eps.harvard.edu/unconf/followups/J10251200-5331109.html ) on June 25.57. The light curve available at the AAVSO database reports visual magnitudes of about V=4.8 on June 27 and 5.8 on July 1st. FERMI LAT reports a detection just a few hours after the optical discovery (Jean et al. Atel #17252) Swift has observed V572 Vel on average every two days, starting on June 26th for about 1.5 ks each time in WT mode. Swift/XRT detected no X-ray source at the position of the transient with an upper limit of 0.017 +/-0.001 cts/s on the observation by June 28th. Using PIMMS and assuming power law emission with the photon index of 2 and HI column density of 0.5x10^22 cm^-2, this translates to the unabsorbed 0.3-10.0 keV flux limit of 3.6x10^-12 ergs/cm^2/s. The optical spectrum reported by Shore et al. (Atel #17256) suggests a similarity with the merger system V1309 Sco, which could explain the non-detection of X-ray emission so far. Further Swift observations are scheduled in the next few days. We thank the Neil Gehrels Swift Observatory team and the PI, Brad Cenko, for supporting the V572 Vel monitoring.