Fermi-LAT Gamma-ray Observations of the Classical Nova V462 Lup 2025

ATel #17249; G. Marti-Devesa (University and INFN Trieste), C. C. Cheung (NRL), P. Fauverge (University of Bordeaux and CNRS) , P. Monti-Guarnieri (University and INFN Trieste), S. Buson (DESY, University of Wuerzburg), R. J. Britto (University of the Free State), G. La Mura (INAF-O. A. Cagliari), and P. Jean (IRAP, Toulouse) on behalf of the Fermi Large Area Telescope Collaboration
on 26 Jun 2025; 21:06 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 target of opportunity (ToO) observations of the classical nova V462 Lup 2025 (ASASSN-25cm; AT 2025nlr; ATel #17228) aimed at increasing exposure on the source during the interval when gamma-ray emission is most expected. Preliminary analysis of the Large Area Telescope (LAT) data from 2025 June 25.0 to 26.0 indicates a gamma-ray excess consistent with the optical position (TNS, R.A. = 227.01364, Dec. = -40.14155, J2000).

Preliminary analysis indicates that this source was detected with ~5 sigma significance with an average flux F(E>100 MeV) = (3.2 +/- 1.1) x 10^-7 ph cm^-2 s^-1 and a power-law photon index of 2.6 +/- 0.3 (statistical errors only). The best-fit LAT position (J2000) is R.A. = 227.066 deg, Dec. = -40.153 deg with a 68% (95%) confidence error radius of 0.23 (0.38) deg. Evidence for gamma-ray emission from a position consistent at 95% confidence level with the new point-source was observed in the previous days, when a ~3 sigma excess was found in 2025 June 20.0 to 21.0, with F(E>100 MeV) = (1.0 +/- 0.7) x 10^-7 ph cm^-2 s^-1 and a power-law photon index of 2.4 +/- 0.5 (statistical errors only).

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 person is 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.