SOAR and SALT spectroscopic follow up of V1047 Cen (Nova Cen 2005)

ATel #12975; E. Aydi, J. Strader, L. Chomiuk, A. Kawash, K. V. Sokolovsky, L. Shishkovsky (MSU) D. A. H. Buckley (SAAO), M. Orio (INAF Padova, UoW) P. Mroz (Warsaw U. Observatory), P. Woudt (UCT), D. P. K. Banerjee (Physical Research Laboratory, Ahmedabad), A. Evans (Keele University), T. R. Geballe (Gemini Observatory), F-J. Hambsch (VVS, BAV, AAVSO), S. Kafka (AAVSO), U. Munari (INAF Astronomical Observatory, Padova), G. Myers (AAVSO), K. L. Page (U. Leicester, UK), S. Starrfield (ASU), F. Walter (Stonybrook), R. D. Gehrz, C. E. Woodward (Minnesota), and R. M. Wagner (OSU, LBT Observatory)
on 1 Aug 2019; 17:50 UT
Credential Certification: Elias Aydi (eaydi@saao.ac.za)

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Nova Cen 2005 (V1047 Cen) was noticed as an optical transient AT2019hik/Gaia19cfn on 2019-06-10 while showing an unexpected long-term rise in brightness that started as early as 2019-04-06 (ATel #12876) and continues up to this moment. The initial spectroscopic observations (ATel #12885, #12893, #12923) suggested that the re-brightening is a slow dwarf nova outburst, similar to the ones displayed by GK Per. The long 8.66 h orbital period suggested from TESS observations (ATel #12889) seemed to fit this picture.

On 2019-07-28.97 UT, we obtained two spectra of low (R ~ 900) and medium (R ~ 5000) resolution using the Goodman spectrograph on the 4.1 m SOAR telescope. On 2019-07-29.73UT we also obtained a 2 x 1000 s spectra using the High Resolution Spectrograph (HRS; Crause et al. 2014, Proc. SPIE, 91476) mounted on the 11m Southern African Large Telescope under the SALT Large Science Program on Transients. The observations were taken in the LR mode of HRS which covers the spectral range of 3800-8900 A at a resolution of R=14000. The SALT spectra were reduced using the SALT HRS MIDAS pipeline (Kniazev et al. 2016, MNRAS 459, 3068).

The spectra show broad emission lines of H I, He I, C IV, and [O III] (as reported in ATel #12885, 12893, 12923). However, the Balmer lines have became significantly stronger than the [O III] lines, in comparison with the previous observations (the peak of Hbeta is comparable to [O III] 5007, while Halpha's peak is 5 times stronger; see below a comparison between the line flux ratios). We measure a FWZI > 5000 km/s for the Balmer lines, while the central emission of these lines show a significant broadening in comparison to previous observations. We also identify P Cygni profiles in some of the He I and H I lines at velocities ~ -1200 km/s (as reported in ATel #12893). The broadening of the Balmer lines along with the ongoing brightening of the system are unusual and worth further investigations. We encourage follow up observations in all bands.

 
June 19, 2019: 
F(Hbeta/[OIII]5007) ~ 0.35 
F(Halpha/[OIII]5007) ~ 3.07 
 
July 28, 2019: 
F(Hbeta/[OIII]5007) ~ 1.58 
F(Halpha/[OIII]5007) ~ 15.0