Rapid evolution of Nova Per 2020 on the rise toward optical maximum

ATel #14229; U. Munari (INAF Padova), P. Ochner (Univ. Padova), P. Valisa and S. Dallaporta (ANS Collaboration)
on 27 Nov 2020; 21:04 UT
Credential Certification: U. Munari (ulisse.munari@oapd.inaf.it)

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Nova Per 2020 has been discovered on Nov 25.807 UT as TCP J04291884+4354232 by Seiji Ueda (Kushiro, Hokkaido, Japan), on images obtained with a Canon EOS 6D digital camera + f/3.2 200-mm lens, and classified as a nova in ATel #14224 based on the presence of broad Balmer lines with P-Cyg absorptions on spectra recorded on Nov 26.05 UT.

We are keeping a tight photometric and spectroscopic monitoring of Nova Per 2020. An extract of the fully transformed photometry so far obtained with ANS Collaboration telescope 0310 is listed in the table below. At the time of writing the nova is still quickly rising in brightness, going from V=10.331 to V=8.594 is 43 hours. Over the same period the color has changed little, from B-V=0.643 to 0.679. The current rate of rise in brightness suggests the maximum may have not been reached yet.

UTNov	B	V	R	I	z	Y
25.956	10.974	10.331	9.847	9.389	9.733	9.674
26.153	10.902	10.224	9.698	9.183	9.522	9.466
26.735	10.242	9.533	9.018	8.529	8.852	8.791
27.179	9.802	9.119	8.624	8.146	8.474	8.399
27.737	9.273	8.594	8.110	7.630	7.960	7.878

Echelle spectra (4200-8900 Ang, resolving power 18,000) have been obtained with Varese 0.84m telescope on Nov 26.813 and 27.703 UT. Low resolution spectra (3300-8000 Ang, 2.31 Ang/pix) were recorded with Asiago 1.22m telescope on Nov 27.004 and 27.715 UT.

The spectra obtained during the rise to maximum on Nov 26.813 and 27.004 show strong P-Cyg features for HeI (4471, 4922, 5016, 5876, 6678, 7065 Ang) and NII (multiplet 3). Marked P-Cyg profiles affect also many other lines, in particular Balmer and OI (7773, 8446). The velocity of the absorption with respect to the emission component is -475 km/s for Hgamma, -558 for Hbeta and OI 7773, -488 for HeI 5876, and -610 for Paschen 12.

The spectral appearance has changed completely the following night, with the nova one mag brighter and closer to maximum. On the spectra for Nov 27.703 and 27.715, all HeI and NI lines have disappeared, replaced by FeII lines of various multiplets, in particular 42, 48 and 49, with pronounced P-Cyg absorption at -750 km/s from emission. Deep P-Cyg profiles are shown also by Balmer and OI lines (-640 km/s for both). The overall appearance of the these later spectra, obtained closer to maximum brightness, is typical of novae of the FeII class.

Sharp and saturated interstellar lines of NaI doublet are observed at -4.7 (+/-0.4) km/s heliocentric velocity. An equivalent width of 0.197 Ang is measured for interstellar KI 7699. This value indicates optically thin conditions and corresponds to E(B-V)=0.77 following the calibration by Munari and Zwitter (1997, A&A 318, 269). A similar E(B-V)=0.82 is obtained from 0.186 Ang equivalent width measured for the diffuse interstellar band at 6614 Ang, which is recorded on the spectra along many other DIBs.