V392 Per turning into a Neon Nova, with marked changes in the three-component line profiles

ATel #11926; U. Munari (INAF Padova) and P. Ochner (UniPD, ANS Collaboration)
on 9 Aug 2018; 13:06 UT
Credential Certification: U. Munari (ulisse.munari@oapd.inaf.it)

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Y. Nakamura (CBET #4514) on UT 2018 April 29.474 discovered the cataclysmic variable V392 Per to have erupted into a nova, peaking at V~6.2. The nova was immediately detected as a strong gamma-ray source by Fermi-LAT (Li et al. ATel #11590), and three months later as an X-ray source when the Sun-constraint was lifted and the nova could be pointed by Swift (Darnley et al. ATel #11905).

On UT Aug. 9.083 we observed Nova V392 Per with the Asiago 67/92cm Schmidt telescope in BVgri bands. Calibration into the APASS photometric system provides B=15.250, V=14.267, g'=14.801, r'=14.000 and i'=13.671, with transformation errors about 0.005 mag in all bands. Simultaneous with the photometric observations, we obtained a deep spectrum of the nova with the Asiago 1.22m telescope, at a dispersion of 2.31 Ang/pix (for a resolving power 1100) and over the wavelength interval 3300-8000 Ang. The mid exposure time was UT Aug 9.061.

Compared to spectral observations just before (Tomov et al., ATel #11605) and soon after the Solar conjunction (Darnley, ATel #11846 and #11872), large changes have occoured. The transition to advanced nebular conditions is in place, with [OIII] 4959+5007 now 3.6 times the integrated flux of Halpha+[NII]. All emission lines result now composed by two broad and well separated components (both with a FWHM ~1800 km/sec; exact values range from 1500 to 2000 km/sec depending from the line). The bluer component is now generally the strongest. The velocity separation of these broad components ranges from 3400 km/s for Halpha up to 4500 km/sec for [NeV] 3426 Ang (well matching the FWHM=5200 km/s of the single peaked line profiles observed at the start of the eruption, Wagner et al., ATel #11588). A narrow and low-velocity component is visible in most of the lines, its width unresolved at our instrumental resolution (thus < 200 km/s). The peak intensity of this central, narrow component (Nw) varies greatly from line to line compared to the intensity of the broad components (BC), ranging from Nw >> BC for HeII 4686, to Nw > BC for HeI lines, Nw ~ BC for Balmer lines, Nw << BC for [NeIII], [OIII], [NII], and absent for [NeV]. Such profiles for the emission lines are closely similar to those observed at late stages in the extremely fast and He/N V2672 Nova Oph 2009, modelled by Munari et al. (2011, MNRAS 410, 525) as a bipolar flow aligned with the line of sight plus an equatorial torus seen face-on.

The large intensity of Neon lines, in particular [NeV] 3426 comparable in intensity to Halpha+[NII], suggest V392 Per to be a Neon Nova. The integrated flux of the two broad components of [NeV] 3426 is 4.5x10(-13) erg/cm2sec, and 3.5x10(-13) for [NeIII] 3869. The integrated flux of the narrow central peak for [NeIII] 3869 is 1.5x10(-14), or 4% of the broad components. [NeIV] 4715 is probably present too, but too heavily blended with HeII 4686 and the NIII 4640 complex for a reliable detection.