Spectroscopy of the Nova AT2026clk obtained in France

ATel #17805; C. Buil, M. Dennefeld, on behalf of the RAPAS group
on 18 May 2026; 12:05 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Michel Dennefeld (dennefel@iap.fr)

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Spectra of AT2026clk were obtained on May17, 2026, by C.Buil (from the STAROS project, and member of RAPAS) with his 0.2m Newton telescope located at Antibes in the south of France. The telescope was equiped with a TinyStar'Ex spectrograph, and two gratings were used, one in the blue, and one in the far red, with a spectral resolution of 1250, covering a total spectral range from 450 to 940nm. The spectrum is typical of a nova in an early phase, with a heavily reddened continuum. Prominent lines of Hydrogen, Helium and OI dominate the spectrum, showing typical PCygni profiles indicating an expansion velocity of ~1800 km/s. Lines of NI,CI,MgII, etc. show multiple components, confirming the findings of Frostig et al. (ATel 17801), but those components are not seen in Hydrogen or OI. The Halpha over Hbeta ratio is measured at 47, indicating heavy reddening, part of which must be due to our own Galaxy (galactic latitude of 2.5 degrees). The ratio of OI lines 844/777 nm is measured at 3.5, suggesting the Nova is of the FeII type (Williams, 1998) although no FeII lines are seen (yet ?). This is confirmed by another spectrum obtained on May 18th at OHP with the 1.93m telescope and its Mistral spectrograph (R~700). It will be interesting to follow this object further, to see if FeII lines appear later (as suggested by Aydi et al. 2024), although the heavy reddening will make the detection of FeII lines in the blue part of the spectrum more difficult. RAPAS is a ProAm collaboration created by T. Midavaine (SAF), W. Thuillot (Paris Observatory-PSL) and M. Dennefeld (IAP/CNRS and Sorbonne U.) and funded by Paris Observatory under an API initiative of its Scientific Council (http://rapas.imcce.fr). STAROS is a group aiming at developing instrumentation for Amateurs Astronomers (https://staros-projects.org).