Optical spectroscopy of the SN impostor PSN J12355216+2755560 outburst
ATel #15808; A. S. Vinokurov, A. F. Valeev, Y. N. Solovyeva, V. N. Aitov (SAO RAS); K. E. Atapin, A. V. Dodin, A. M. Tatarnikov, N. I. Shatsky (SAI MSU)
on 14 Dec 2022; 13:50 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Azamat Valeev (azamat@sao.ru)
Subjects: Optical, Transient, Variables
We report on the first results of the photometric and spectroscopic analysis of the recent outburst of the "SN impostor" PSN J12355216+2755560 (=AT 2016blu, TCP J12355222+2755559). The V-band photometric observations were carried out on 1 December 2022 and from 7 through 11 December 2022 with the 2.5-m telescope of CMO SAI MSU and with the 1-m telescope of SAO RAS (Russia). To measure the object's magnitude, we performed relative photometry using 8 reference stars, the photometric error ranges from 0.02 to 0.08 mag depending on the instrument, atmospheric conditions and seeing. The absolute calibration was done using the HST image taken on 9 March 2005 with the ACS/WFC camera in the F550M filter, the calibration accuracy is about 0.1 mag. The interstellar extinction is taken equal to the Galactic value AV = 0.05 mag.
The brightness maximum of V=16.4 mag was observed on 9 December (MJD=59922.06), it is brighter or comparable to previous object outbursts (Atels #6303, #8755). The outburst profile is similar to that described in Atel #8755, it had a rapid increase (within two days) and then a decrease (of 3 days) by approximately 2 mag. The light curve is listed in the table below (the uncertainties include only errors of the relative photometry).
The spectroscopy was carried out on 1 and 2 December 2022 with the 6-m telescope of SAO RAS, and on 10 and 12 December with the 2.5-m telescope of CMO SAI MSU. Both instruments have approximately the same spectral range and resolution (~ 3600-7400 ÅÅ and ~ 4 Å respectively). The 6-m telescope spectra indicate very broad Balmer hydrogen and neutral helium lines, all with P Cyg profiles. The relatively weak absorption components show blue wings extending up to velocities ~5000-6000 km/s. The main change in the spectrum of 10th December compared to the previous one is a significant increase in depths of the absorption components, which made it possible to estimate the velocity more accurately as 6400 ±200 km/s, using the blue wings of the HeI 5875, Hα, Hβ and Hγ lines. There is no obvious double-peaked shape of absorptions in contrast to that was observed earlier (Atels #14460, #14638). In the spectrum of 12th December, the line profiles have changed due to the appearance of a new very broad emission component, which is most prominent in the Hα line.
59914.11 17.92 +- 0.02 (2.5m CMO)
59920.07 18.32 +- 0.05 (1m SAO)
59921.06 17.03 +- 0.08 (1m SAO)
59922.06 16.37 +- 0.04 (2.5m CMO)
59922.14 16.41 +- 0.03 (1m SAO)
59923.08 17.64 +- 0.04 (2.5m CMO)
59924.99 18.48 +- 0.03 (2.5m CMO)
