Swift Observations of V1452 Tau - Emission from Beryllium (7Be II) Revealed ?

ATel #18073; C. E. Woodward (U. Minnesota, USA), P. Kuin (Mullard Space Science Labs, UK), K. L. Page (U. Leicester, UK), L. Izzo (INAF, Osservatorio Astronomico di Capodimonte), P. Molaro (INAF, Osservatorio Astronomico di Trieste), S. Starrfield (Arizona State U., USA)
on 22 Sep 2026; 23:38 UT
Credential Certification: C.E. Woodward (chickw024@gmail.com)

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The galactic nova V1452 Tau (TCP J05210763+2338194) was discovered on 2026-Aug-06 (ATel# 17947; day 0) and subsequently spectroscopically classified as FeII-type nova (ATel# 17950). The AAVSO V-band light curve, which reached a maximum of near 8.7 mag roughly six days after discovery, exhibits an oscillatory behavior and a very slow decline from maximum light. Here we report Swift UVOT grism observations obtained on 2026-Sept-14 (day 39) when the V-band magnitude of the nova was near 11.4. These data reveal several emission lines including the Mg II (doublet) complex at 279.88nm and a complex at 313.13nm which we tentatively identify as the 7Be II (doublet). In some novae, this feature is identified as the O III 313.37nm line; however, the Swift spectrum on day 39 shows no strong evidence of other expected Bowen fluorescence oxygen lines (e.g., Sevelli et al. 2007, A&A 464, 715; Selvelli et al. 2018, MNRAS 481, 2261) and lines of helium are absent or below the detectability threshold. Observed fluxes in select lines (erg/s/cm2) are Mg II (279.88nm) 2.7e-12, 7Be II (313.13nm) 0.7e-12, H I-delta (410.28nm) 1.9e-12, O III (425.72nm) 0.7e-12, H I-gamma (434.168nm) 2.3e-12, and N I (465.313nm) 1.8e-12 (all wavelengths cited in vacuum). The Swift UV magnitudes on 2026-Sept-14 are: m2 13.61 +/- 0.03, w2 13.26 +/- 0.03 and average w1 11.91 +/- 0.02. No X-ray emission is yet detected to a 3-sigma upper limit of 4.8e-3 count/s in 1.7 kilo-seconds of exposure. The super-soft-phase (SSS) of evolution likely has not yet occurred. Further observations across the electromagnetic spectrum are encouraged. The investigators thank the Swift MOC for scheduling these DDT observations.