Recent news in the world of cataclysmic variables

The second part of 2020 I spent on my Slovak observatory in Kolonica performing the usual observing programs. There is always something interesting on the sky. Let me highlight 3 spectacular objects which attracted attention during this period. Read the stories of SS Cyg, V1391 Cas and V1112 Per.

SS Cyg

One of the most intensively observed variable stars. Prototype of long orbital period dwarf novae. And there is still space for surprise. The anomalous behavior started already in 2019. The outbursts became irregular, quiescence brighter. The optical irregularities are accompanied by increased flux in X rays. This was the reason for international observing campaign leaded by Dr. Mariko Kimura (RIKEN, Japan). My contribution were time series observations with high time resolution showing the rapid variations. See Figure 3. The analysis is not finished yet. Dr. Kimura just announced that the hot spot can be excluded as the source of this rapid variations.

Fig. 1 Optical light curve in V band in recent period. Data from AAVSO International Database.

Fig. 2 For the comparison the normal behavior in previous years. V band CCD and visual observations from AAVSO International Database.

Fig 3. One of time series observations on 1 meter VNT telescope.

V1391 Cas = Nova Cas 2020

Nova Cas 2020 was discovered by Stanislav Korotkiy and Kirill Sokolovsky at unfiltered magnitude 12.9 (V zero-point) on 2020 July 27. It was classified spectroscopicaly as an FeII type classical nova. It was later given a definitive designation V1391 Cas. I started simultaneous photometric and spectroscopic observations just after the return from Madeira island. The photometry is provided by 14″ Schmidt-Cassegrain telescope equipped with MII G2-1600 CCD camera and B, V, Rc, Ic filters. Low resolution spectra (R~1000) are acquired using 11″ Schmidt-Cassegrain telescope and LISA spectrograph. The nova spent ~ 3 months fluctuating around maximum, then evolved to the dust forming phase in 2020 December. It is too faint for small size telescopes during this episode. But after the recovery it can appear again on 14 – 15 mag in V band. So I encourage to keep the attention on this interesting object. The preliminary results were presented at the Conference about Variable Stars Research in Czech Republic. See: http://var.kozmos.sk/files/praha2020dpv.pdf.

Figure 4. V1391 Cas light curve in B V Rc and Ic bands from the AAVSO International database.

Figure 5. CCD observations of V1391 Cas in Kolonica

Figure 6. Photometric and spectroscopic coverage of the nova V1391 Cas eruption. DPV means my observations. Note the different density of coverage due to the good weather in the summer and cloudy weather later in the autumn.

Figure 7. Identification of spectral lines in spectra taken at different stages of the nova V1391 Cas eruption.

Figure 8. Evolution of spectral lines during the nova V1391 Cas eruption. Animation based only on spectra taken in Kolonica.

V1112 Per

Another well positioned nova for northern hemisphere observers. Statistically the novae are concentrated to the galactic center in Sagitarius. Obviously they are usually to low on the sky in the northern part of the Earth. And now we how simultaneously one nova in Cassiopeia and another in Perseus. The later much more faster as one can see from the overall light curve on the Figure 10.