Spectroscopic classification of TCP J18573095+1653396 as a nova bordering naked-eye brightness

ATel #14704; U. Munari (INAF Padova), P. Valisa and S. Dallaporta (ANS Collaboration)
on 12 Jun 2021; 21:44 UT
Credential Certification: U. Munari (ulisse.munari@oapd.inaf.it)

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TCP J18573095+1653396 (=ZTF19aasfsjq) has been discovered on 2021 June 12.537 UT at mag. 8.4 by Seiji Ueda (Kushiro, Hokkaido, Japan).

We have obtained a high resolution Echelle spectrum of TCP J18573095+1653396 with the Varese 0.84m telescope on Jun 12.84 UT (resolving power 20,000, range 4250-8900 Ang) and a low resolution spectrum with the Asiago 1.22m + B&C (3300-8000 Ang, 2.31 Ang/pix) on June 12.85 UT.

The spectrum has an overall blue shape and shows very pronounced broad absorptions (FWHM about 3000 km/s) compatible with P-Cyg components for Halpha, Hbeta and Hgamma blue-shifted by about 3100 km/s. A feeble emission component is visible at the position expected for Halpha, with a FWHM of 2100 km/s. Similarly broad (~3000 km/s) and similarly blue-shifted (by about 2700 km/s) absorptions seems to affect HeI lines (4471, 5876, 7065 Ang). The strongest absorption is centered around 6295 Ang, with a FWHM of 2700 km/s. Overall, the spectrum could be compatible with a nova of unusual large velocity.

Numerous interstellar absorption features are clearly visible, in particular the atomic KI 7699 and NaI doublet and the diffuse interstellar bands at 5780, 5797, and 6614. Adopting the calibration by Munari and Zwitter (1997, A&A 318, 269), the equivalent width of KI 7699 translates to a reddening E(B-V)=0.55.

We have also observed TCP J18573095+1653396 with ANS Collaboration telescope IR 0310 on Jun 12.90 UT, and obtained the photometric values B=6.903, V=6.184, R=5.749, and I=5.232. The color B-V=0.719 confirms the above derived reddening when compared with the intrinsic colors of novae given by van den Bergh & Younger (1987, A&AS 70, 125).