Additional Optical Spectroscopy of PNV J18040967-1803581 Indicates a Slow Fe II-type Classical Nova

ATel #11573; R. M. Wagner (LBTO and OSU), C. E. Woodward (Minnesota), S. Starrfield (Arizona State), M. J. Darnley (LJMU), L. Izzo (IAA-CSIC), M. Henze (SDSU), and J. Rupert (MDM Observatory)
on 25 Apr 2018; 17:26 UT
Credential Certification: R. Mark Wagner (rmw@as.arizona.edu)

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Following our initial report (ATEL #11528), we continued to follow the spectroscopic evolution of PNV J18040967-1803581 (CBET No. 4507), a possible classical nova or stellar merger event. In addition to our first spectrum obtained on 2018 April 10.444 UT and reported on ATEL #11528, we obtained additional optical spectra (range: 396-687 nm; resolution 0.3 nm) on 2018 April 12.466, 15.450, and 22.434 with the 2.4 m Hiltner telescope (+OSMOS) of the MDM Observatory on Kitt Peak. The four epochs are shown from bottom to top in the montage at the link below.

The most recent spectra show considerable strengthening of the emission components of Hα, Hβ, Fe II multiplets of 27, 37, 38, 42, 46, 48, 49, 55, and 74, and Na I D1 and D2. The spectrum is now consistent with that of a slow Fe II-type classical nova during the early decline phase in agreement with that reported by Joshi, Srivastava, and Banerjee (ATEL #11570) based on a near-infrared spectrum obtained on 2018 April 14.96. The optical emission lines still continue to exhibit P Cygni-type line profiles. On April 10, 15, and 22, the center of the blue-shifted absorption component of Hα is displaced by -617, -608 and -780 km/s respectively with respect to the fitted emission component. The FWHM of Hα emission corresponds to 774, 1500, and 1700 km/s respectively on the same dates. The equivalent width of the Hα emission component on April 22 was -44 nm.

Additional optical and infrared observations of PNV J18040967-1803581 are encouraged given the likelihood of dust formation (ATEL #11570).

Spectroscopic evolution of PNV J18040967-1803581 between 2018 April 10.4 and 22.4 UT