Spectroscopic Classification of the Transients PNV J00425220+4116246 = AT 2021bfs and PNV J00434645+4133408 = AT 2021boa as classical novae in M31

ATel #14370; Kenta Taguchi, Keisuke Isogai, Naoto Kojiguchi, Yusuke Tampo (Kyoto University), Claudio Balcon (ISSP)
on 5 Feb 2021; 04:39 UT
Credential Certification: Keisuke Isogai (isogai@kusastro.kyoto-u.ac.jp)

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We report on spectra of the transients PNV J00425220+4116246 (= AT 2021bfs = ZTF21aagkzmc) and PNV J00434645+4133408 (= AT 2021boa = ZTF21aagkzve). We obtained the spectra from 2021-02-04.40 UT to 2021-02-04.44 UT by using a fiber-fed integral field spectrograph (KOOLS-IFU; Matsubayashi et al. 2019) mounted on the 3.8-m telescope Seimei (Kurita et al. 2020) at Okayama Observatory of Kyoto University.

As reported to CBAT, PNV J00425220+4116246 was discovered by the Italian Supernovae Search Project (ISSP) at 17.6 ± 0.5 mag (unfiltered) on 2021-01-26.7209 UT. According to TNS, it was not detected on 2021-01-24.7889 by ISSP (limiting mag = 19) and by orange-ATLAS on 2021-01-25.2360 (limiting mag = 13.81, which is too small to be regarded as the last non-detection). It has brightened and was detected by ZTF at g = 15.960 on 2021-02-03.136 UT, g = 16.07 on 2021-02-05.14 UT, and r = 16.04 on 2021-02-05.16 UT. This object is located nearby (1 arcmin distant from) the center of M31. Our spectrum on 2021-02-04.4 UT shows broad Balmer emission lines and also Fe II emission lines around 5000 Å. So, we conclude this object is a Fe II-type nova in M31.

PNV J00434645+4133408 was discovered by XOSS at 16.8 mag (unfiltered) on 2021-02-03.5801, as reported to CBAT. It was also detected by ZTF at g = 17.274 ± 0.039 on 2021-02-03.136. It was not detected by XOSS on 2021-02-01.5752 (limiting mag = 18.5). Then, ZTF reported that this object was at g = 17.26 on 2021-02-05.14 UT and r = 17.09 on 2021-02-05.16 UT. This object is located about 20 arcmins from the center of M31. Our spectrum on 2021-02-04.4 UT shows broad Balmer emission lines. Moreover, features of Fe II emission lines around 5000 Å are similar to those of the previous one. So, we conclude this object is also a Fe II-type nova in M31.