Near-Infrared Observations of V7993 Sagittarii (TCP J18022164-3310319)

ATel #17122; Vishal Joshi, Dipankar P. K. Banerjee, Mudit Srivastava (Physical Research Laboratory, India)
on 31 Mar 2025; 12:19 UT
Credential Certification: Vishal Joshi (vjoshi@prl.res.in)

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V7993 Sagittarii (TCP J18022164-3310319) was identified as a transient by Korotkiy et al. (CBAT Transient Object Followup Reports) on 2025 March 24.056 UT. An independent discovery was reported by Tadashi Kojima on 2025 March 23.764 UT. (CBET 5531). Y. Tampo obtained a low-resolution optical spectrum (R ~ 400), classifying the transient as a classical nova (ATel #17108). We conducted near-infrared (NIR) photometric and spectroscopic observations using the Near-Infrared Camera Spectrograph (NICS) instrument on the 1.2m telescope at Mount Abu Observatory. Observations were performed on 2025 March 26.97 UT and 2025 March 27.95 UT. The resulting photometric magnitudes are given below, indicating a nova that is still brightening:

• Date: 2025 March 26.95 UT
  • J: 7.26 ± 0.13 mag
  • H: 6.76 ± 0.10 mag
  • Ks: 6.54 ± 0.06 mag
• Date: 2025 March 27.93 UT
  • J: 6.90 ± 0.15 mag
  • H: 6.35 ± 0.12 mag
  • Ks: 6.07 ± 0.09 mag

NIR spectra at R ~ 1000 were obtained, covering the wavelength ranges 0.86 - 1.81 um on 2025 March 26.99 UT and 1.11 - 2.40 um on 2025 March 27.97 UT. The highly reddened spectra exhibit prominent lines of hydrogen, oxygen, and carbon, all of which display P Cygni profiles with a significantly stronger absorption component compared to the emission component. Overall, the spectral characteristics are consistent with those of a Fe II class nova in its very early phase (Banerjee and Ashok, 2012, BASI, 40, 243). The velocity separation between the absorption and emission component of the Paschen beta 1.2818 um line is approximately 700 km/s which is in agreement with the outflow velocity derived from the optical spectrum reported by Y. Tampo (ATel #17108). Further observations are planned.