V462 Lup has entered the super-soft X-ray phase
ATel #17436; G. J. M. Luna (UNAHUR/CONICET/Argentina), K. L. Page (U. Leicester), N. P. M. Kuin (MSSL), Isabel de J. Lima (UNESP/Brazil), Claudia V. Rodrigues (INPE/Brazil) and N. E. Nunez (ICATE/UNSJ/Argentina)
on 6 Oct 2025; 19:07 UT
Credential Certification: Gerardo Juan Manuel Luna (juan.luna@unahur.edu.ar)
V462 Lup (Nova Lupi 2025; ASASSN-25cm; AT 2025nlr) was discovered as a bright nova on 2025 June 12 at 20:52:48 UT (https://www.wis-tns.org/object/2025nlr).
Since then the Neil Gehrels Swift Observatory regularly observed it and detected an X-ray source on August 22 2025. Combining further observations obtained until September 18 2025, we found a mean count rate of 0.0076 +/- 0.0011 counts/s. This spectrum can be modeled with an absorbed optically-thin plasma with kT > 1.3 keV, NH = 7.4 +9.0/-4.1 e22 cm^-2 and unabsorbed flux in the 0.3-10 keV energy range of 1.23e-12 erg/s/cm^2.
A new Swift/XRT observation obtained on October 4 2025 revealed a new super-soft X-ray component at a count rate of 0.024 +0.004/-0.003 count s^-1 that can be modeled with a combination of an absorbed blackbody-like optically thick X-ray emission plus an optically thin thermal plasma, with parameters kT > 7 keV, BB kT = 30 +14/-8 eV, NH=7.12e20 cm^-2 and unabsorbed flux in the 0.3-10 keV energy range of 3.56e-12 erg cm^-2 s^-1.
The Swift/UVOT observation yielded a magnitude in the UVW2 filter of 10.97 +/- 0.03 (stat) +/- 0.03 (sys). The ultraviolet spectrum is similar but overall weaker than that obtained on August 22 2025 and reported in Page et al. (Atel #17353).
Unfortunately, the source is going into Sun constraint for Swift until December 30 2025, so further observation will be requested by then. We thank the Swift PI, Brad Cenko, and his deputies for approving the time, as well as the Swift planning and operations teams for their continuing support.
