Spectroscopic Classification of PNV J23244760+6111140 as a classical nova (further reports)

ATel #14472; Kenta Taguchi (Kyoto University), Hiroyuki Maehara (National Astronomical Observatory of Japan), Keisuke Isogai, Yusuke Tampo, Naoto Kojiguchi, Taichi Kato, Daisaku Nogami (Kyoto University)
on 19 Mar 2021; 12:06 UT
Credential Certification: Keisuke Isogai (isogai@kusastro.kyoto-u.ac.jp)

Tweet

We further report on our follow-up observations (which partially include ATel #14471) of the nova PNV J23244760+6111140. We obtained the spectra from 2021-03-18.820 UT to 2021-03-18.850 UT using the fiber-fed integral field spectrograph (KOOLS-IFU; Matsubayashi et al. 2019) mounted on the 3.8-m Seimei telescope (Kurita et al. 2020). We also performed multicolor photometry using the 0.4-m telescope at Kyoto University.

As reported to CBAT, this transient was discovered by Yuji Nakamura at 9.6 mag (unfiltered) on 2021-03-18.4236 UT. S. Korotkiy et al. reported pre-outburst at 13.53 mag (unfiltered with V zero-point) on 2021-03-14.71. The discovered position is very close (distant only ∼1.3'') to that of a known W UMa-type eclipsing variable star CzeV3217 = Gaia EDR3 2015451512907540480, whose orbital period is 0.376938 days and whose distance is 1.69 ± 0.07 kpc (i.e. m - M = 11.13 mag). N. Ikonnikava and K. Sokolovsky confirmed that the position of the transient coincides with that of CzeV3217.

Before the outburst, it was g = 15.67, r = 15.46, i = 15.44, y = 15.32, and z = 15.36, according to Pan-STARRS, and was U = 15.3 according to IGAPS point source catalogue. According to ASAS-SN Sky Patrol, this was m_V ∼ 15 and M_V ∼ 4 before the outburst, which is typical for a novalike variable. The color is also consistent with a CV suffering from reddening (E (g - r) = 0.42 mag, according to Beyestar19; Green et al. 2019). The presence of orbital variation in the bright novalike phase suggests that this object has a relatively large (but not sufficient to show deep eclipses) orbital inclination.

Several multicolor photometries are reported. N. Ikonnikova and K. Sokolovsky reported the results of their preliminary photometries: B = 9.58, V = 9.27, and Rc = 8.87 on 2021-03-18.68 (CBAT). T. Vanmunster reported B = 9.36, V = 8.95, R = 8.45, I = 8.12 (vsnet-alert 25560) (The reported time of 2021-03-18.31 is wrong. The corrected time is 2021-03-18.81.). Our photometry was performed on 2021-03-18.85, and found that this object was B = 9.105, V = 8.460, Rc = 8.190, and Ic = 8.014, respectively. Using the Gaia distance, it was M_V = -2.68, is still faint for a classical nova. Our photometry and the one by N. Ikonnikova and K. Sokolovsky reveal that this object brightened by Δm_V = -0.81 mag and Δm_B = -0.47 mag in just 0.17 days. (m_B - m_V) of the three photometries were 0.31, 0.41, and 0.645 respectively, meaning that it cooled during then.

As we already reported to ATel #14471, our spectra show emission lines of Balmer series, N III 4640, and He II 4686, and He I emission lines with P-Cyg profiles (the blue curve is the same data as ATel #14471 but we reanalyzed it.). We further find and identify N II 5679, C III 5695, and Paschen emission lines. O. Ohshima reported a spectrum taken by the 30-cm telescope in Ohshima Tamashima Observatory, which confirms our results.

Our spectra and photometric data prefer this object is a classical nova in the rapid brightening stage. Highly ionized emission lines in our spectra indicate that the photosphere of the nova has not expanded enough to cool itself. We predict as the photosphere expands, this nova will cool and brighten further in optical bands, and be dominated by emission lines with lower excitation levels (such as Fe II).

Our Spectra