Follow-up spectroscopic observations of Nova Sge 2026 (V488 Sge) with WHUT
ATel #18022; Sai-En Xu, Yi-Fei Qu, Bei You (Wuhan University), on behalf of the Wuhan University One-Meter Optical Telescope team.
on 31 Aug 2026; 12:02 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Bei You (youbei@whu.edu.cn)
Referred to by ATel #: 18028
Nova Sge 2026 (V488 Sge) was discovered by the NMW-TexasTech survey on 2026-08-25.12 UT (ATel #18009). Follow-up spectroscopic observations were conducted, as reported in ATel #18008 and ATel #18012, confirming it as a Fe II-type nova. Rapid photometric and spectroscopic evolution was subsequently reported in ATel #18021, including a rapid decline in optical brightness and substantial spectral changes within a few days.
We performed follow-up spectroscopy with the Wuhan University One-Meter Optical Telescope (WHUT) on 2026 August 29 - 30 UT. The observations cover approximately 4100 - 9000 Angstrom in three B/G/R spectral channels, with a resolving power of R around 1000. The spectra obtained on August 29 and 30, together with the corresponding flux-ratio spectrum and candidate line identifications, are shown in the accompanying material.
Date (UTC) | Channel | Exposure time
2026-08-29.69 | B/G/R | 1 x 300 s
2026-08-30.78 | B/G/R | 2 x 300 s
The spectral morphology observed on August 29.69 UT is broadly consistent with the August 29.82 UT spectrum reported in ATel #18021, showing strong Balmer and Fe II emission. Prominent emission features, including O I lambda 7774, O I lambda 8446, and the blended Ca II infrared triplet and H I Paschen emission in the 8500â8700 Angstrom region, are also revealed in our spectra.
A comparison of the August 29.69 and August 30.78 spectra reveals differential evolution between the optical continuum and the emission features. Measurements in several continuum windows indicate that the continuum decreased by approximately 30% over this interval. Approximate fixed-window measurements indicate that the Fe II emission complex faded at a rate comparable to the continuum, whereas the Balmer and O I features generally evolved more slowly. Specifically, H-beta, H-gamma, and O I lambda7774 showed moderate declines, while H-alpha and O I lambda 8446 changed only slightly. The structured blend around 8200 - 8250 Angstrom showed a decline broadly similar to that of the adjacent continuum. Given the broad and blended nature of several features and the uncertainties in absolute flux calibration, these relative changes should be regarded as approximate.
Further observations are planned to monitor its continued evolution.
The Wuhan University One-Meter Optical Telescope (WHUT) at the Lenghu Observatory, owned and operated by Wuhan University, is a Ritchey-Chretien system featuring a compact instrument package that integrates both a multi-band photometric camera and a low-resolution spectrograph. For access to raw data or to discuss potential collaboration, please contact Bei You (youbei@whu.edu.cn).
Spectra obtained on August 29 and 30
