Fermi-LAT Gamma-ray Observations of the Probable Nova V572 Velorum

ATel #17252; P. Jean (IRAP, Toulouse), G. Marti-Devesa (University and INFN Trieste), P. Fauverge (University of Bordeaux and CNRS), C. C. Cheung (NRL) on behalf of the Fermi Large Area Telescope Collaboration
on 27 Jun 2025; 22:17 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Guillem Marti-Devesa (guillem.marti-devesa@ts.infn.it)

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We report Fermi Gamma-ray Space Telescope observations of the probable nova V572 Velorum (PNV J10251200-5331109) discovered on 2025-06-25.440 (CBET #5574). Preliminary analysis of the Large Area Telescope (LAT) data from 2025-06-25 07:45 to 2025-06-27 13:02 indicates a gamma-ray excess consistent with the optical position (CBET #5574; R.A. = 156.3079 deg, Dec. = -53.5219 deg, J2000).

Preliminary analysis indicates that this source was detected with ~5.5 sigma significance with an average flux F(E>100 MeV) = (2.2+/- 0.9) x 10^-7 ph cm^-2 s^-1 and a power-law photon index of 2.2 +/- 0.2 (statistical errors only). The best-fit LAT position (J2000) is R.A. = 156.35 deg, Dec. = -53.63 deg with a 68% (95%) confidence error radius of 0.11 (0.18) deg. The signal is only significantly detected after 2025-06-27 00:00, with F(E>100 MeV) = (6.4+/-2.0) x 10^-7 ph cm^-2 s^-1 and a power-law photon index of 2.2 +/- 0.2 (statistical errors only). Before that time no gamma-ray excess is found, with a 95% confidence upper limit on the photon flux of F(E>100 MeV) < 2.6 x 10^-7 ph cm^-2 s^-1 for a power-law photon index of 2.0.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. We encourage multi-wavelength observations. For this source the Fermi LAT contact people are P. Jean (pjean at irap.omp.eu) and C.C. Cheung (Teddy.Cheung at nrl.navy.mil).

The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.